Anatomy of the Skull PDF

OUTLINE 1. The skull Frontal, occipital and sphenoid bone  SKULL The skull is the bony skeleton of the head and most complex osseous structure in the body. The vertebrate skull is modified part of the axial skeleton together with...

OUTLINE 1. The skull Frontal, occipital and sphenoid bone  SKULL The skull is the bony skeleton of the head and most complex osseous structure in the body. The vertebrate skull is modified part of the axial skeleton together with vertebral column, ribs and sternum. The skull is composed of 28 separate bones, of which most are paired, but some in the median plane are single. The majority of bones in the skull are held by fibrous joints termed sutures. The skull can be subdivided into cranium and mandible, based upon the fact that most of bones of the skull articulate by fixed joints, mandible is easily detached. The skull can be divided into – neurocranium and viscerocranium. The neurocranium protects the brain and organs of special sense and viscerocranium is associated with the cranial parts of the respiratory and digestive tract. Neurocranium is devided into the upper part termed the calvaria or calva (skull “cap”) and inferior part basis cranii or the base of the cranium. The cranial cavity contains the brain, pineal and hypophyseal (pituitary) gland, parts of cranial nerves, blood vessels, meninges and cerebrospinal fluid. The important nerves and vessels pass in and out of the skull via openings termed foramina. Many of the bones are flat, irregular or pneumatic. The cranial bones consist of two thin plates of compact bones: outer and inner tables, separated by diploe. Trabecular bones contain red bone marrow.  FRONTAL BONE Frontal bone is like half a shallow, irregular cap forming the forehead or frons. The frontal bone is pneumatic bone (frontal sinus). The frontal bone has two parts: vertical and horizontal part. Each part has external and internal surface. VERTICAL – SQUAMOUS PART OF THE FRONTAL BONE This forms the major portion of the bone. The squamous part has two surfaces: external and internal. External surface External surface of the vertical or squamous part has rounded frontal tuber (tuberosity) about 3 cm above the midpoint of each supra-orbital margins. These tubera are especially prominent in young skulls and in adult females. Below them, are two curved superciliary arches, medially joined by a smooth median elevated glabella; they are more prominent in males. The supra-orbital margins of the orbital openings lie inferiorly to the superciliary arches. On their medial thirds is a supra-orbital notch (or foramen) containing supraorbital vessels and nerve. Medially to it is a small frontal notch or foramen. The supra-orbital margin ends laterally into the zygomatic process that meets the zygomatic bone. From here a line – temporal line curves postero-superiorly. The area of the frontal bone below and behind the temporal line is known as temporal surface and forms the anterior part of the temporal fossa. The region between supra-orbital margins is the nasal part. Internal surface Internal surface of the vertical part is concave. Its upper, median part has a vertical groove for the superior sagittal sinus, the edges of which unite below as the frontal crest. Groove contains the superior sagittal sinus and crest ends with a foramen caecum. Several granular foveolae for arachnoid granulations usually exist along the groove for the superior sagittal sinus. Internal surface of the horizontal part shows impressions for cerebral gyri and small furrows for meningeal vessels. HORIZONTAL PART External surface of the horizontal part of the frontal bone is divided into two orbital and one nasal part. Orbital parts The orbital parts of the frontal bone are two thin, triangular laminae which are separated by wide ethmoidal notch. The orbital surface of each plate is concave with antero-lateral fossa for the lacrimal gland. Behind the medial end of the supra-orbital margin is the trochlear fovea (or spine), for attachment of a fibrocartilaginous trochlea for the superior oblique muscle of the eyeball. The cerebral (or internal) surface is convex and marked by frontal gyri and faint grooves for meningeal vessels. Nasal part The region between the supra-orbital margins is the nasal part. The serrated nasal notch (or nasal border) articulates with the nasal bones, maxillary frontal processes and lacrimal bones. The region ends into the nasal spine. Lateral to the nasal spine are placed the openings of frontal sinuses. Behind the nasal spine is wide, quadrilateral ethmoidal notch. Several ethmoidal air cells are visible along its lateral margins. Two transverse grooves across each margin are converted into anterior and posterior ethmoidal canals by the ethmoid bone; these canals open on the medial orbital wall, transmitting anterior and posterior ethmoidal nerves and vessels. Border The parietal (posterior) margin is thick, deeply serrated. FRONTAL SINUS Frontal sinus is paired structure which consists of two irregular cavities placed behind the superciliary arches. Each communicates with the middle meatus of the nasal cavity.  OCCIPITAL BONE Occipital bone forms the back and base of the cranium. It has four parts which enclose the foramen magnum; the plate postero-superior to foramen is the squama (squamous part), the massive quadrilateral part anterior to it is the basilar part (basi-occipital); on each side of the foramen is the lateral part (exoccipital). SQUAMA The squama is convex externally and concave internally. The squama has two surfaces: external and internal. The external surface presents, the external occipital protuberance. On each side two curved lines extend laterally from it: the highest nuchal line and the superior nuchal line. From the external occipital protuberance the median external occipital crest descends to the foramen magnum. On each side an inferior nuchal line spreads laterally from the crest‫׳‬s midpoint. The squama‫׳‬s internal surface is divided into four deep fossae by an internal occipital protuberance and by sagittal and horizontal extensions from it. The two superior fossae are triangular and adapted to the cerebral occipital poles, the inferior are quadrilateral and adapted to the cerebellar hemispheres. A wide groove ascends from the protuberance – groove for the superior sagittal sinus. An internal occipital crest descends from the protuberance. On each side a wide groove for the transverse sinus extends laterally from the protuberance. Angles The squama has angles: superior angle and two lateral angles (marked internally by ends of the grooves for the transverse sinuses). Borders The squama has two borders. The lambdoid border extends from the superior to the lateral angles, and articulates with the occipital borders of the parietal bones, forming the lambdoid suture. The mastoid borders extend from lateral angles to the jugular processes, articulating with the mastoid parts of temporal bones. BASILAR PART The basilar part extends anteriorly from the foramen magnum, fusing with the sphenoid in adults (spheno-occipital synchondrosis). This part has two surfaces: Inferior surface of the basilar part has a small pharyngeal tubercle for attachment of the fibrous pharyngeal raphe, about 1 cm anterior to foramen magnum. Superior surface of the basilar part is a broad groove and forms part of the clivus, which ascends anteriorly from the foramen magnum. On its lateral margins are grooves for the inferior petrosal sinuses, below which the lateral margins articulate with petrous parts of the temporal bones. LATERAL (CONDYLAR) PARTS The lateral (condylar) parts of the occipital bone flank the foramen magnum. On their inferior surface are occipital condyles for articulation with superior facets of the atlas. There are oval or kidney like shaped. Behind each condyle is condylar fossa. Its floor is sometimes perforated by a condylar canal. On the superior surface an oval jugular tuberculum. It overlies the hypoglossal canal, which transmits the hypoglossal nerve and meningeal branch of the ascending pharyngeal artery. Laterally to the jugular tuberculum is jugular process, quadrilateral plate, lined by a jugular notch. This notch is sometimes divided by small intrajugular process. Jugular notch, together with the same structure on the petrous part of the temporal bone, forms the jugular foramen. On the superior surface of the jugular process a deep groove ends at the jugular notch, it contains the end of the sigmoid sinus (groove for the sigmoid sinus).  SPHENOID BONE Sphenoid bone lies in the base of the skull, among the frontal, temporal and occipital bone. It has body, paired greater and lesser wings and two pterygoid processes, descending from junctions of the body and greater wings. The body contains sphenoidal sinuses. BODY The body is cuboidal in shape (it has six surfaces) and it contains two paranasal sphenoidal sinuses. Cerebral or superior surface Anteriorly, on the cerebral or superior surface the jugum sphenoidale is placed. Jugum sphenoidale is bounded behind by the prechiasmatic sulcus, leading laterally to the optic canals. Posterior to it lies the Turkish saddle (sella turcica), which consists of: tuberculum sellae, hypophysial fossa (containing the pituitary gland) and dorsum sellae. The tuberulum sellae is completed laterally by two middle clinoid processes and dorsum sellae by two posterior clinoid processes. Posterior surface Posteriorly to the dorsum sellae, the sphenoidal body, together with the basilar part of the occipital bone, forms the clivus. Lateral surfaces The body‫׳‬s lateral surfaces have carotid sulcuses, which accommodate the internal carotid artery and cavernous sinus. Anterior surface On the anterior surface lies the sphenoidal crest. Its joints the ethmoid bone. On each side of the crest is an opening of the sphenoidal sinus. The sphenoidal sinuses are closed antero-inferiorly by sphenoidal conchae. Inferior surface The body‫׳‬s inferior surface bears a median triangular sphenoidal rostrum, which articulates with the vomer. On each side of the posterior part of the rostrum a thin vaginal process is placed. LESSER WINGS The lesser wings are triangular in shape, protruding laterally from the superior margin of the body. The lesser wing is connected to the body by anterior and posterior root. Between roots lies the optic canal, containing the optic nerve and ophthalmic artery. The suprior surface of each wing is a smooth. The inferior surface, together with the greater wing, forms the superior orbital fissure. On the medial end of the posterior border of the lesser wings anterior clinoid processes are located. Superior orbital fissure, triangular in shape, connects middle cranial with orbital cavity. It is bounded medially by sphenoidal body, superiorly by the inferior surface of the lesser wing and inferiorly by the orbital surface of the greater wing. GREATER WINGS The greater wing is connected to the body by three roots. Between anterior and middle root is foramen rotundum (transmitting the maxillary nerve); between middle and posterior root is foramen ovale (transmitting the mandibular nerve). On the spine of the sphenoid bone is foramen spinosum (transmitting the middle meningeal artery and meningeal branch of the mandibular nerve). The greater wings have two surfaces: cerebral and lateral surface. The crebral surface participates in formation of the middle cranial fossa. The lateral surface is, further, divided into four surfaces. Temporal surface (which participates in formation of the temporal fossa) and infratemporal surface (which participates in formation of the infratemporal fossa) are divided by a transverse infratemporal crest. Orbital surface forms the lateral wall of the orbital cavity and participates in formation of the superior, as well as inferior orbital fissurae and maxillary surface participates in formation of the pterygopalatine fossa. PTERYGOID PROCESSES The pterygoid processes descend perpendicularly from the junctions of greater wings and body. Each consists of a medial and lateral plate, which upper parts are fused anteriorly. Below, the plates are separated by pterygoid notch and posteriorly they diverge in the pterygoid fossa, in which is the medial pterygoid muscle attached. Above is the small, oval scaphoid fossa (for the tensor veli palatini muscle attachment), formed by division of the upper posterior border of the medial plate. The anterior surface of the root of the pterygoid process is pierced by the anterior orifice of the pterygoid canal. The lateral pterygoid plate is thin. Its lateral surface is part of the medial wall of the infratemporal fossa. Its medial surface is the pterygoid fossa‫׳‬s lateral wall. Also, it has anterior and posterior border. The medial pterygoid plate is narrower and longer. Its lower end curves into pterygoid hamulus. The lateral surface is the pterygoid fossa‫׳‬s medial wall. The medial surface participates in formation of the posterior nasal aperture. Also, it has anterior and posterior border. The medial plate is prolonged above on the sphenoid body‫׳‬s inferior aspect as the thin vaginal process, connecting anteriorly with the sphenoidal process of the palatine bone (in that way they form the palatovaginal canal) and medially with the ala of the vomer (in that way they form the vomerovaginal canal). SPHENOIDAL SINUS Sphenoidal sinus is undeveloped at birth. Pneumatization begins at the age of three and progress posteriorly.  OUTLINE 2. Ethmoid, parietal and temporal bone  ETHMOID BONE Ethmoid bone lies in the anterior part of the cranial base and participates in formation of the medial wall of the orbits, as well as the roof, lateral and medial wall of the nasal cavity. It has a horizontal, perforated cribriform plate, a median perpendicular plate and two lateral labyrinths which contain ethmoidal air cells. CRIBRIFORM PLATE fills the ethmoidal notch of the frontal bone and forms a large part of the roof of the nasal cavity. It is penetrated by numerous foramina. A triangular median crista galli projects up from this lamina; its anterior border has two small alae, completing the foramen caecum, described with the frontal bone. PERPENDICULAR PLATE, thin and quadrilateral descends from the cribriform plate to form the upper part of the nasal septum. Its anterior border is attached to the nasal septal cartilage; its posterior border joining the sphenoidal crest; its inferior border meets the vomer; its superior border is fused with the cribriform plate, as well as with the nasal spine of the frontal bone and the nasal bone. ETHMOIDAL LABYRINTHS consist of thin-walled ethmoidal air cells, classified in the anterior, middle and posterior group. The lateral surface or orbital plate of the labyrinth is part of the medial orbital wall, the medial being part of lateral nasal wall. The superior surface shows open air cells. It is crossed by two grooves completing anterior and posterior ethmoidal canals with the frontal bone. On the posterior surface air cells are completed by the sphenoidal conchae and orbital process of the palatine bone. The medial surface of the labyrinth forms part of the lateral nasal wall and end as the convoluted middle nasal concha (forming the middle nasal meatus). Above this the surface shows the thin, curved superior nasal concha (forming the superior nasal meatus). Posterior ethmoidal air cells open into this meatus. The conchae curve infero-medially, each roofing a meatus, which open into the nasal cavity. Concha’s superior border articulates with the medial surface of the labyrinth and its free lower border is gently curved. The superior concha is thin, curved lamina, superior to the middle concha. It roofs the superior nasal meatus. The middle concha is larger and it extends above the middle nasal meatus. Middle ethmoidal air cells produce a swelling called bulla ethmoidalis which is placed on the lateral wall of the middle meatus. A thin, curved uncinate process, variable in size, projects postero-inferiorly from the labyrinth and below bulla ethmoidalis. Uncinate process crosses the ostium of the maxillary sinus to join the etmoidal process of the inferior nasal concha. The curved gap between process and bulla is the semilunar hiatus. At its upper end it is in continuous with the ethmoidal infundibulum. Infundibulum communicates with the anterior and middle group of ethmoidal air cells, frontal and maxillary sinus. ETHMOIDAL SINUS The ethmoidal cells (sinuses) are present at birth. By two years of age they are recognizable through the use of CT scanning.  PARIETAL BONE Parietal bone forms the most of the cranial roof and sides. Quadrilateral in shape, each bone has two surfaces, four borders and four angles. Surfaces 1. External surface is convex, with a central parietal tuber (tuberosity). Curved superior and inferior temporal lines cross it, forming two arches. To the superior arch is attached the temporal fascia and to the inferior arch is attached the temporalis. Posteriorly close to the sagittal (superior) border a parietal foramen is placed (sometimes it could be absent). 2. Concave internal surface is marked by cerebral gyri and grooves for the middle meningeal vessels. Along the sagittal border is a groove for the superior sagittal sinus, completed by the opposite parietal bone. Granular foveolae for arachnoid granulations flank the groove for the sagittal sinus. Borders 1. Serrated sagittal border, longest and thickest, articulates with the opposite parietal bone and participates in formation of the sagittal suture. 2. Squamous (inferior) border articulates with sphenoid bone. 3. Frontal border is deeply serrated and articulates with the frontal bone to form half of the coronal suture. 4. Occipital border, deeply serrated, articulates with the occipital bone, forming half of the lambdoid suture. Angles 1. Frontal (antero-superior) angle is at the BREGMA (meeting of the sagittal and coronal sutures). 2. Spenoidal (antero-inferior) angle (PTERION), meeting the frontal bone and greater sphenoid wing. 3. Occipital (postero-superior) angle is at the LAMBDA, the meeting of sagittal and lambdoid sutures. 4. Mastoid (postero-inferior) angle (ASETERION) articulates with the occipital and mastoid process of the temporal bone.  TEMPORAL BONE Temporal bones are placed in the sides of the calvaria and the base of the skull. It belongs to flat and pneumatic bones. Each temporal bone consists of four components: the squamous, petromastoid and tympanic part, as well as the styloid process. SQUAMOUS PART The squamous part is thin. It has vertical and horizontal part. Vertical part Its external surface is convex and forms the part of the temporal fossa for the attachment of temporalis. Also, it shows the groove for middle temporal artery. The supramastoid crest curves backwards and upwards across its posterior part. The suprameatal triangle lies in the anterior end of the supramastoid crest. The triangle usually contains a small suprameatal spine anteriorly. The internal (cerebral) surface of the squamous part is concave. This surface shows grooves for the branches of middle meningeal vessels. Its lower border is fused to the anterior region of the petrous part. The superior border is thin and joints the inferior border of the parietal bone. Posteriorly it forms an angle with the mastoid element. Horizontal part The horizontal part of the squamous part consists of the zygomatic process and mandibular fossa. Zygomatic process The zygomatic process extends forward from the lower region of the squamous part. The posterior part of the zygomatic process is bounded by anterior and posterior roots. The anterior root is forming an articular tubercle. The posterior root is small, conical postglenoidal tubercle, prolonged forwards above the external acoustic meatus. Its upper border continues into the supramastoid crest. The anterior part of the zygomatic process is thin and flat. The anterior end is serrated and articulates with the temporal process of the zygomatic bone, forming zygomatic arch. Mandibular fossa The mandibular fossa is limited by the articular tubercle of the zygomatic process. It presents an anterior articular area, formed by the squamous part, and a posterior, non-articular area, formed by the tympanic element. Posteriorly, the mandibular fossa is separated from the tympanic part by the squamotympanic fissure. Medially, a projection from the petrous part of the temporal bone (tegmen tympani) goes through the squamotympanic fissure further dividing it into petrotympanic and petrosquamosus fissures. PETROMASTOID PART Petrous part It has a base, apex, three surfaces (anterior, posterior and inferior) and three borders (anterior, posterior and superior). It contains the acoustic labyrinth. The base corresponds to the mastoid processes. The apex is irregular in shape. It shows the internal opening of the carotid canal and limits the foramen lacerum posteriorly (with the greater wing of the sphenoid and the basilar part of the occipital bone). Anterior surface contributes to the floor of the middle cranial fossa. Behind the apex is a trigeminal impression for trigeminal ganglion. The arcuate eminence is raised by the anterior semicircular canal; laterally and anteriorly to it is placed the tegmen tympani (roof of the tympanic cavity). Anteriorly, tegmen bears groove for the greater petrosal nerve which passes to enter the bone by hiatus for the greater petrosal nerve. Groove and hiatus for the lesser petrosal nerve are placed in front of the latter structures. Posterior surface shows the internal acoustic opening near its center. Behind it lies the opening of vestibular canaliculus and above it is the subarcuate fossa. The irregular inferior surface is part of the external surface of the base of the cranium. Near the apex of the petrous part is a quadrilateral area which is associated with the attachment of muscles. Behind this region is the large circular external opening of the carotid canal, behind which is the jugular fossa which contain the superior bulb of the internal jugular vein. Superior border is the longest and is grooved by the superior petrosal sinus. Posterior border is intermediate in length. Together with the occipital bone jugular fossa contributes to the jugular foramen. The jugular foramen is divided into two parts. Anterior part transmitting nerves (IX, X XI cranial nerve) and posterior part is place where sigmoid sinus continues as internal jugular vein and descends into the neck. Mastoid part This is posterior region of the temporal bone. This part projects down as mastoid process. It has three surfaces. Outer or lateral surface shows the mastoid foramen, which is variable size and position. Internal surface of the mastoid process bears a deep groove for the sigmoid sulcus. Inferior surface contains the deep mastoid notch for the posterior belly of digastric muscle attachment and the occipital groove, in which occipital artery runs. It is located medially to the notch. Superior border of the mastoid part is serrated for the articulation with the mastoid angle of the parietal bone. Posterior border, serrated as well, articulates with the occipital bone. TYMPANIC PART The tympanic part of the temporal bone is part below the squamous part and in front of the mastoid process. The bony part of the external acoustic meatus is about 16 mm long. Its medial end is closed by tympanic membrane (placed in the tympanic sulcus) and the outer end is bounded by the posterior zygomatic root (the postglenoid tubercle), superiorly. Inferior border is sharp and form the sheath of the styloid process (vaginal process). Between the styloid and mastoid process the stylomastoid foramen is placed, the external end of the facial canal which transmits the facial nerve and stylomastoid artery. The cartilaginous part of the external acoustic meatus is attached to the lateral surface of the bony part. STYLOID PROCESS The styloid process projects antero-inferiorly from the inferior aspect of the temporal bone. Its length is variable. The process is covered laterally by the parotid gland; the facial nerve crosses its base, the external carotid artery its tip. Medially, the process is separated from the beginning of the internal jugular vein by the attachment of stylopharyngeus.  OUTLINE 3. FACIAL BONES  MAXILLA Maxillae hold the upper teeth, both together form the upper jaw, and connect on the left and right with the zygomatic bones (cheek bones). Each assists in forming the boundaries of three cavities, namely, the roof of the oral cavity, the floor and lateral wall of the nasal cavity and the floor of the orbit. The maxilla also enters into the formation of two fossae, the infratemporal and pterygopalatine, and two fissures, the inferior orbital and pterygomaxillary. Each bone consists of a body and four processes, frontal, alveolar, zygomatic and palatine. The body (‘corpus maxillae’) The body is pyramidal in shape, and contains a large cavity, the maxillary sinus. It has base, nasal surface, apex and three surfaces - an anterior or facial, a posterior or infratemporal, a superior or orbital. Surfaces of the body The anterior surface is directed anterolaterally. Just above of the canine teeth is a depression, the canine fossa. Above the fossa is the infraorbital foramen, the end of the infraorbital canal; it transmits the infraorbital vessels and nerve. Medially, the anterior surface is limited by a deep concavity, the nasal notch, which with its fellow of the opposite side forms the anterior nasal spine. The infratemporal surface is convex, directed posterolaterally and forms part of the infratemporal fossa. It is separated from the anterior surface by the zygomatic process and by a strong ridge, extending upward from the socket of the first molar tooth. It is pierced about its center by the alveolar foramina, the apertures of the alveolar canals, which transmit the posterior superior alveolar vessels and nerves. At the lower part of this surface is a rounded eminence, the maxillary tuberosity. The orbital surface is a thin plate of bone, which forms the floor of the orbit. Immediately deep to this thin plate is the maxillary sinus. Near the middle of the posterior part of the orbital surface is the infraorbital groove, for the passage of the infraorbital vessels and nerve. The groove passes forward, and ends in an infraorbital canal. The canal opens into the anterior surface as the infraorbital foramen. The nasal surface presents a large, irregular opening, maxillary hiatus, leading into the maxillary sinus. Below the aperture is a smooth concavity which forms part of the inferior meatus of the nasal cavity, and behind it is a rough surface for articulation with the perpendicular plate of the palatine bone; this surface is traversed by a greater palatine groove. Groove is converted into a greater palatine canal by the perpendicular plate. In front of the opening of the sinus is deep groove, the lacrimal groove, which makes up about two-thirds of the cicrumference of the nasolacrimal canal. The rest of the canal is contributed by the lacrimal bone and inferior nasal concha; this canal opens into the inferior meatus of the nose and transmits the nasolacrimal duct, which transports tears from the orbit to the nasal cavity. More anteriorly is an oblique ridge, the conchal crest, for articulation with the inferior nasal concha. The frontal process ('processus frontalis; nasal process') Its lateral surface is divided by vertical anterior lacrimal crest, which is continuous below with the infraorbital margine of the body. The smooth area anterior to the anterior lacrimal crest merges below with the anterior surface of the body of the maxilla. Behind the crest, a vertical groove combines with one on the lacrimal bone to complete the lacrimal fossa. Its medial surface forms part of the lateral wall of the nasal cavity. A rough subapical area articulates with the ethmoidal bone, below this is the ethmoidal crest, the posterior end of which articulates with the middle nasal concha. The upper border articulates with the frontal bone and the anterior with the nasal; the posterior border is thick, and hollowed into a groove, which is continuous below with the lacrimal groove on the nasal surface of the body. The zygomatic process ('processus zygomaticus; malar process') The zygomatic process extends laterally to the zygomatic bone. In front it forms part of the anterior surface; behind, it is concave, and forms part of the infratemporal fossa; above, it is serrated for articulation with the zygomatic bone; while below, it presents the prominent arched border which marks the division between the anterior and infratemporal surfaces. The zygomatic process is the apex of the pyramid. The alveolar process ('processus alveolaris') The alveolar process of booth maxillae form the upper alveolar (dental) arch. The alveolar process forms the sockets and supporting bone for the maxillary teeth. These cavities dental alveoli are separated by interalveolar septa. They are eight in number, and vary in size and depth according to the teeth they contain. That for the canine tooth is the deepest; those for the molars are the widest, and are subdivided into minor cavities by interradicular septa; those for the incisors are single, but deep and narrow. The palatine process ('processus palatinus; palatal process') The palatine process, is horizontal and projects medially from the nasal surface of the bone. It forms a considerable part of the floor of the nose and the roof of the mouth. The superior surface of the palatine process is concave from side to side, smooth, and forms the greater part of the floor of the nasal cavity. It presents, close to its medial margin, the upper orifice of the incisive canal. The lateral border of the process is continuous with the body of the maxilla. The medial border is thicker in front than behind, and is raised above into a ridge, the nasal crest, which, with the corresponding ridge of the opposite bone, forms a groove for the reception of the vomer. The front of this ridge rises to a considerable height, and is named the incisor crest; it is prolonged forward into a sharp process, which forms, together with a similar process of the opposite bone, the anterior nasal spine. The posterior border is serrated for articulation with the horizontal part of the palatine bone (the transverse palatine suture). Its inferior surface is concave, and forms, with the palatine process of the opposite bone, the anterior three-fourths of the bony palate. The inferior surface displays palatine spines and palatine grooves for the transmission of the descending palatine vessels and nerve. The medial border articulates with the palatine process of the opposite bone, and forms the median palatine suture. The lateral border of the process is continuous with the rest of the bone. When the two maxillae are articulated, a tunnel-shaped opening, the incisive foramen, is seen in the middle line, immediately behind the incisor teeth. In this opening the orifices of two lateral canals are visible; they are named the incisive canals. On the under surface of the palatine process, a delicate linear suture, well seen in young skulls, may sometimes be noticed extending anterolaterally on either side from the incisive foramen to the interval between the lateral incisor and the canine tooth. The small part in front of this suture constitutes the premaxilla (os incisivum), which in most vertebrates forms an independent bone; it includes the whole thickness of the alveolus, the corresponding part of the floor of the nose and the anterior nasal spine, and contains the sockets of the incisor teeth. The maxillary sinus ('sinus maxillaris') The maxillary sinus is a large pyramidal cavity within the body of the maxilla: its apex extends into the zygomatic process and the base, medial wall, forms part of the lateral wall of the nasal cavity. Its walls are everywhere exceedingly thin, and correspond to the nasal, orbital, anterior, and infratemporal surfaces of the body of the bone. Its nasal wall, or base, presents a large, irregular aperture, communicating with the nasal cavity. In the articulated skull this aperture is much reduced in size by the following bones: the uncinate process of the ethmoid above, the ethmoidal process of the inferior nasal concha below, the vertical part of the palatine behind, and a small part of the lacrimal bone. It usually opens into the posterior part of the middle meatus of the nose, generally by two small apertures left between the above-mentioned bones. Usually only one small opening exists, near the upper part of the cavity; the other is closed by mucous membrane. The floor is formed by the alveolar process and part of the palatine process of the maxilla and the roof contributes the major part of the floor of the orbit. Anterior wall forms anterior, facial surface, and posterior wall is formed by infratemporal surface of the maxilla. The infraorbital canal usually projects into the cavity as a well-marked ridge extending from the roof to the anterior wall. On the posterior wall are the alveolar canals, transmitting the posterior superior alveolar vessels and nerves to the molar teeth. The size of the cavity varies in different skulls, and even on the two sides of the same skull. Changes produced in the maxilla by age At birth the transverse and anteroposterior diameters of the bone are each greater than the vertical. The frontal process is well-marked and the body of the bone consists of little more than the alveolar process, the teeth sockets reaching almost to the floor of the orbit. The maxillary sinus presents the appearance of a furrow on the lateral wall of the nose. In the adult the vertical diameter is the greatest reflecting the development of the alveolar process and enlargement of the sinus. In old age the bone reverts in some measure to the infantile condition; its height is diminished, and after the loss of the teeth the alveolar process is absorbed, and the lower part of the bone contracted and reduced in thickness. MANDIBLE The mandible is the largest, strongest and lowest bone in the face. It holds the lower teeth in place and articulates with the temporal bones of the skull at the temporomandibular movable synovial joints. It has a horizontally curved body that is convex forwards, and two broad rami, that ascend posteriorly. The junction of the posterior border of the ramus and the lower border of the body forms the prominent angle of the mandible. The body of mandible The body is U-shaped and has external and internal surfaces separated by upper and lower borders. Anteriorly, the external surface shows an inconstant faint median ridge, which indicates fusion of the halves of the fetal bone at the mandibular symphysis (symphysis menti). It is present at birth and begins to fuse in the first year of life, resulting in one mandible. Inferiorly, this ridge divides to enclose a mental triangle. Its base forms mental protuberance which eds on each side as a mental tubercle. The mental protuberance and mental tubercles constitute the chin. The mental foramen, from which the mental nerve and vessels emerge, is situated below either the interval between the premolar teeth, or the second premolar tooth. The external oblique line is a ridge of bone, which originates at the mental tubercle and sweeps upward and posteriorly to become the sharp anterior border of the ramus. A number of muscles of facial expresion are attached to the external surface of the mandible. The internal surface is divided by an oblique mylohyoid line, sharp and distinct near the molars, but faint in front. It extends from a point a centimetre from the upper border behind the third molar to the mental symphysis. To the mylohyoid line is attached mylohyoid muscle (and above its posterior end the superior pharyngeal constrictor, some fascicles of the buccinator, and the pterygomandibular raphe behind the third molar). Below this line is the slightly concave submandibular fossa which adjoins submandibular salivary gland. The area above the mylohyoid line widens anteriorly into a triangular sublingual fossa related to the sublingual gland. Above the mylohyoid line, medial to the molar roots, a rounded torus mandibularis – mandibular torus sometimes appears. In the midline of the body is a small elevation, often divided into upper and lower parts, the superior and inferior mental spines (or genial spine). The superior mental spine gives attachment to the genioglossus, and the inferior mental spine to the geniohyoid. The upper border, the alveolar part, contains 16 dental sockets, or the dental alveoli, for the roots of the lower teeth. It consists of lateral, or buccal (also called facial), and medial, or lingual, plates of bone joined transversely by interdental and interradicular septa. Interalveolar septa form individual sockets between the roots of adjacent teeth. Interradicular septa form individual sockets for the multirooted teeth. The roots cause on external surface of mandible bulges called alveolar yokes. The external surface of the alveolus adjacent to the molar teeth gives attachment to buccinator. If the teeth are lost, alveolar bone is resorbed and the mandibular canal and mental foramen come to lie nearer the superior border. The lower border of the body, the base, extends posterolaterally from the mandibular symphysis into the lower border of the ramus behind the third molar tooth. It can be palpated in its entirety just deep to the skin. Near the midline, on each side, is a rough digastric fossa that gives attachment to the anterior belly of the digastric muscle. The facial artery usually curls round the base of the mandible, sometimes making a shallow groove. The ramus of mandible The mandibular ramus is quadrilateral, and has two surfaces (lateral and medial), four borders (superior, inferior, anterior and posterior) and two processes (coronoid and condylar). The lateral surface is relatively fetureless and bears the oblique ridges in its lower part providing attachment for masseter (masseteric tuberosity). The medial surface presents, a little above centre, an irregular mandibular foramen, leading into the mandibular canal, curving down and forwards into the body. Anteromedially the foramen is overlapped by a thin, triangular, and tonguelike lingula. Attached to it is the sphenomandibular ligament. The mylohyoid groove runs downward and forward from the inferior border of the mandibular foramen, below the posterior part of the mylohyoid line. Occupying this groove are the nerve and vessels to the mylohyoid muscle. The medial surface of the ramus receives the medial pterygoid on the roughened area postero-inferior to the mylohyoid groove (pterygoid tuberosity). The thin superior border bounds the mandibular incisure (or the mandibular notch) surmounted in front by the somewhat triangular, flat coronoid process and behind by a strong condylar process. The inferior border of the mandibular ramus is continuous with the mandibular base. It is typically everted in males, but in females is frequently inverted. The anterior border is thin above where it is continuous with that of the coronoid process, and thicker below where it is continuous with the oblique line. The temporal crest is a ridge of bone on the internal surface of the ramus, paralelly to its anterior border. It runs down from the tip of the coronoid process to the third molar tooth where it divides into two ridges, lateral and medial. The retromolar fossa, is the depression between the lateral and medial ridges of temporal crest and the third molar. This landmark is extremly important in locating the site of injection for an anesthetic block of the inferior alveolar nerve. The posterior border, thick and rounded, extends from the condyle to the angle, being gently convex backwards above, and concave below. It is in contact with the parotid gland. The coronoid process is sharp and projects up slightly forwards. Its margins and medial surface are attachments for most of the temporalis. The condylar process consists of the head and neck. The head is covered by fibrocartilage and articulates with reciprocally shaped mandibular fossa of the temporal bone. It is convex in all directions with greater transverse dimension. Its lateral aspect is palpable in front of the auricular tragus. Below the head is the narrower neck. The neck’s anterior surface bears a rough pterygoid fovea which receives the lateral pterygoid. Its medial surface is related to the auriculotemporal nerve and maxillary artery. The mandibular canal The mandibular canal is the continuation of the mandibular foramen deep into the mandible. It runs obliquely inferiorly and anteriorly through the ramus and body just below the roots of the mandibular teeth with which it communicates by small canals. The canal ends at the midline. It carries the inferior alveolar nerve and vessels from which branches enter dental roots, periodontal sockets and septa. Between the roots of the first and second premolars, or below the second, the canal divides into mental and incisive parts. The mental canal swerves up, back and laterally to the mental foramen, and the incisive canal continues below the incisor teeth. INFERIOR NASAL CONCHA The inferior nasal concha is curved horizontal lamina in the lateral nasal wall. It has two surfaces, medial and lateral, two borders, superior and inferior and two ends, anterior and posterior. The medial surface is convex, and lateral is concave forming internal wall of the inferior nasal meatus. The superior border is divided into three regions; anterior articulating with the conchal crest of the maxilla, posterior articulating with the conchal crest of the palatine bone, and the middle part with three processes, variable in size and form. The lacrimal process is small and articulates with descending process from the lacrimal bone, it forms part of the nasolacrimal canal. Most posteriorly, a thin ethmoidal process articulates with uncinate process of the ethmoidal bone. In the midlle part of the superior border there is maxillary process. It curves inferolaterally to articulate with medial surface of the maxilla at the opening of the maxillary sinus. The inferior border is thick. LACRIMAL BONE The lacrimal bone is the smallest of the cranial bones. It lies anteriorly in the medial wall of the orbit. It has two surfaces, medial and lateral, and four borders, superior, inferior, posterior and anterior. The lateral (orbital) surface is divided by a vertical posterior lacrimal crest. Anterior to the crest there is vertical groove and the anterior edge of the groove meets the posterior border of the frontal process of the maxilla to complete the fossa for the lacrimal sac. The medial wall of the groove is prolonged by a descending process that contributes to the formation of the nasolacrimal canal by joining the maxilla and lacrimal process of inferior nasal concha. A part of the lateral surface behind the lacrimal crest extends inferiorly into the lacrimal hamulus, which, together with maxilla, completes the upper opening of the nasolacrimal canal. The anterior lacrimal border articulates with the frontal process of the maxilla, the posterior border with orbital plate of the ethmoid bone, the superior border with the frontal bone and the inferior border with the orbital surface of the maxilla.  NASAL BONE Two nasal bones are small, oblong, variable in size and form, and placed side by side between the frontal processes of the maxillae. They form the nasal bridge. Each nasal bone has two surfaces, external and internal, and four borders, superior, inferior, lateral and medial. The external surface is convex and internal concave. The superior border articulates with frontal bone. Thin inferior border is continuous with lateral nasal cartilage. The lateral border joins the frontal process of the maxilla and medial meet its fellow. VOMER The vomer is thin, flat and almost trapezoid. It forms posteroinferior part of the nasal septum. It has two surfaces and four borders, superior, inferior, anterior and posterior. Both surfaces are marked by grooves for nerves and vessels. The tick superior border bears alae separated by deep groove. The inferior border articulates with median nasal crests of the maxillae and the palatine bones. The anterior border is the longest and articulates in its upper half with the perpendicular plate of the ethmoid bone. The posterior border is concave, separating the posterior nasal apertures. ZYGOMATIC BONE Each zygomatic bone forms the prominence of a cheek, contributes to the floor and lateral wall of the orbit and the walls of the temporal and infratemporal fossae, and completes the zygomatic arch. It is described as having three surfaces, five borders and two processes. The surfaces are lateral, posteromedial and orbital. The lateral (facial) surface is convex. Its upper part bears zygomaticofacial foramen for the zygomaticofacial nerve and vessels. The posteromedial (temporal) surface articulates anteriorly with zygomatic process of the maxilla, and greater posterior smooth part extends up posteriorly on its frontal process forming anterior wall of temporal fossa. This surface bears the zygomaticotemporal foramen. The orbital surface is smooth and concave and forms anterolateral ppart of the orbital floor and adjacent lateral wall. It bears zygomatico-orbital foramen which leads into the zygomatic canal. The concave anterosuperior (orbital) border forms inferolateral part of the orbital opening. The anteroinferior (maxillary) border articulates with the maxilla. The posterosuperior (temporal) is convex above and concave below. The posteroinferior border serves as attachment of masseter. The posteromedial border articulates with the greater wing of the sphenoidal bone above and maxilla below. The frontal process articulates above with the zygomatic process of the frontal bone and behind with greater wing of the sphenoidal bone.  The temporal process, directed backwards, articulates with zygomatic process of the temporal bone to complete the zygomatic arch. PALATINE BONE The palatine bone is paired bone, posteriorly placed in the nasal cavity between the maxilla and the pterygoid process of the sphenoidal bone. It contributes to the floor and lateral wall of the nose, to the floor of the orbit, to the pterygopalanine and pterygoid fossae. It is irregular in shape with two plates, horizontal and perpendicular, arranged as an L- shape, and three processes, pyramidal, orbital and sphenoidal. Horizontal plate The horizontal plate is guadrilateral, with two surfaces, nasal and palatine, and four borders, anterior, posterior, lateral and medial. The nasal, superior surface is concave, and forms the posterior part of the nasal floor. The palatine, inferior surface, with its fellow, forms the posterior quarter of the bony palate. The posterior border is thin and concave. Medially, with its fellow from the opposite side, the posterior border forms a median posterior nasal spine. The anterior border articulates with the palatine process of the maxilla. The lateral border is continuous with the perpendicular plate of the palatine bone. The medial border articulates with its fellow in the midline and forms posterior part of the nasal crest which articulates with the posterior part of the lower edge of the vomer. Perpendicular plate The perpendicular plate is thin and has two surfaces, nasal and maxillary, and four borders, anterior, posterior, superior and inferior. The nasal, medial surface bears two crests, conchal and ethmoidal. Inferiorly, the nasal surface is concave where it contributes to part of the inferior nasal meatus. Above this is horizontal crest that articulates with inferior nasal concha. Above the conchal crest there is shallow depression which forms a part of the middle nasal meatus. This depression is limited above by an ethmoidal crest for the middle nasal concha, above which a narrow, horizontal groove forms part of the superior nasal meatus. The maxillary, lateral surface is largely rough and irregular and articulates with nasal surface of the maxilla. Posterosuperiorly it forms a smooth medial wall to the pterygopalatine fossa. Its anterior area, also smooth, overlaps the maxillary hiatus from behind to form a posterior part of the medial wall of the maxillary sinus. Posteriorly on the maxillary surface there is deep descending greater palatine groove. This groove is converted into the canal by the maxilla. The greater palatine canal transmits the greater palatine vessels and nerv. The anterior border is thin and irregular. Level with the conchal crest, a pointed lamina projects below and behind the maxillary process of the inferior concha and articulates with it and so appears in the medial wall of the maxillary sinus. The posterior border articulates with medial pterygoid plate.  Orbital and sphenoidal processes project from the superior border, and are separated by the sphenopalatine notch (converted into a foramen by articulation with the body of the sphenoid). The inferior border is continuous with the lateral border of the horizontal plate. Pyramidal process The pyramidal process slopes down posterolaterally from the junction of the horizontal and perpendicular palatine plates into the angle between the pterygoid plates of the sphenoid bone. On its posterior surface there is a smooth, grooved triangular area which completes, with pterygoid plates, the pterygoid fossa. Orbital process The orbital process is directed superolaterally from the anterosuperior angle of the perpendicular plate. It has three articular and two non-articular surfaces. It articulates with maxilla, sphenoidal and ethmoidal bones. Of the non-articular, the superior orbital forms small posterior part of the orbital floor. The lateral surface forms part of the anterior wall of the ptreygopalatine fossa. Sphenoidal process The sphenoidal process is a thin plate that is directed superomedially from the superoposterior angle of the perpendicular plate. Its superior surface articulates with sphanoidal bone (body and root of the medial pterygoid plate). The lateral surface with its anterior smooth pars forms part of the medial wall of the pterygoid fossa. The inferomedial surface forms part of root and lateral wall of the nose. HYOID BONE The hyoid bone is a small bone that has the shape of the horseshoe, or the letter U. It is placed in the anterior side of the neck, between the mandible and the larynx. Main parts of the hyoid bone are the body and two paired processes, the greater and the lesser horns. The body has two surfaces, anterior and posterior and two borders, superior and inferior. The greater horns project posteriorly and superiorly from the body and the lesser horns start superiorly from the place where greater horns joins the body. The hyoid bone connects the floor of the oral cavity in front with the pharynx behind and the larynx bellow.  OUTLINE 4. CRANIO-FACIAL CAVITIES NEONATAL CRANIUM TEMPORAL FOSSA The temporal fossa is a narrow fan-shaped space that cover the lateral surface of the skull. It is limited above by a pair of temporal lines that extend across the skull from the zygomatic process of the frontal bone to the supramastoid crest of the temporal bone. INFRATEMPORAL FOSSA The wedge-shaped infratemporal fossa is inferior to the temporal fossa and middle cranial fossa and deep to the ramus of the mandible. It has four walls, anterior, medial, lateral and superior wall or the roof and is open to the neck posteroinferiorly. The anterior wall is formed by the posterior, infratemporal surface of the maxilla, contains the alveolar foramina. Along the superior border of the anterior wall there is lateral part of the inferior orbital fissure. The lateral wall is formed by medial surface of the ramus of the mandible. It bears the opening to the mandibular canal. The medial wall is formed by lateral plate of the pterygoid process of the sphenoid bone. It contains the pterygomaxillary fissure anteriorly, which is communication between the infratemporal and pterygopalatine fossae. The superior wall, or roof is formed by inferior, infratemporal surface of the greater wing of the sphenoid. Lateral to the infratemporal crest of the greater wing of the sphenoid the infratemporal fossa communicates through the zygomatic foramen with the temporal fossa superiorly. The zygomatic foramen is space between the infratemporal crest of the greater wing medially and zygomatic arch laterally. The major structures which occupy the infratemporal fossa are medial and lateral pterygoid muscles, the maxillary artery, the mandibular nerve, chorda tympani branch of the facial nerve, the parasympathetic otic ganglion and the pterygoid venous plexus. PTERYGOPALATINE FOSSA The pterygopalatine fossa is an inverted “tear-drop” shaped space between bones on the lateral side of the skull immediately posterior to the maxilla and anterior to the pterygid process of the sphenoid. It is placed laterally to the nasal cavity, medially to the infratemporal fossa. Shaped like four-sided pyramid, it has three walls, anterior, medial and posterior, (the lateral wall is missed), the base or the roof, turned upward and apex turned downward. The anterior wall is formed by the posterior surface of the maxilla. Along the superior border of the anterior surface there is medial part of the superior orbital fissure. The medial wall is formed by the lateral surface of the perpendicular plate of the palatine bone. In the upper part of this surface there is sphenopalatine foramen, the communication with the nasal cavity. The posterior wall is formed by the anterosuperior surface of the pterygoid process and the upper part of the posterior wall is formed by the maxillary surface of the greater wing of the sphenoid bone. It bears the foramen rotundum (communication with middle cranial fossa) and more medial and inferior small foramen, the anterior opening of the pterygoid canal. Laterally the pterygopalatine fossa communicates with infratemporal fossa through the pterygomaxillary fissure. The roof is formed by the inferior surface of the body of the sphenoid bone. The apex of the pterygopalatine fossa extends inferiorly in to the greater palatine canal, which is communication with oral cavity. Major contents of the pterygopalatine fossa are the maxillary nerve, the pterygopalatine ganglion and the terminal part of the maxillary artery. NASAL CAVITY The two nasal cavities are the irregular spaces between the roof of the mouth and the cranial base, divided by bony vertical septum that is approximately median in position. Lateral to the nasal cavities are orbits. Each nasal cavity has superior wall or roof, inferior wall or floor, lateral wall and medial or septal wall and two openings, anterior and posterior. The cavity is wider below than the above, and widest and vertically deepest in its central region. Bones that contribute to the skeletal framework of the nasal cavities include: - the unpaired ethmoid, sphenoid, frontal bone and vomer - the paired nasal, palatine and lacrimal bones, maxillae and inferior nasal conchae. Of all the bones associated with the nasal cavities, the ethmoid is a key element. Roof The roof is horizontal. Its anterior part is formed by the nasal spine of the frontal bones and the nasal bones. The central part is formed by the cribriforme plate of the ethmoid bone which separates the nasal cavity from the anterior cranial fossa. Posteriorly, the roof is formed by the anterior and inferior surfaces of the body of the sphenoid. At the junction of the cribriforme plate of the ethmoid and the body of the sphenoid there is spheno-ethmoidal recess. Floor The floor of the nasal cavity or bony palate is smooth, concave and slopes up from anterior to posterior apertures. Anteriorly, the palatine processes of the maxillae and, behind them, the horizontal plates of the palatine bones, articulate in the midline and with each other. The nasal floor is therefore crossed at the junction of its middle and posterior thirds by the transverse palatine suture and in the midline, at the junction of the two halves of the bony palate there is median palatine suture. Medial wall The medial wall of the nasal cavity is the bony nasal septum which is placed vertically in the median sagittal plane and separates the right and left nasal cavities from each other. It is formed primarily by the vomer and the perpendicular plate of the ethmoid. The vomer extends from the body of the sphenoid to the bony palate, forming the posteroinferior part of the septum (including the posterior border). The perpendicular plate of the ethmoid forms the anterosuperior part of the bony nasal septum. The nasal septum is often deviated, more usually to the left. Lateral wall The lateral wall is formed largely by the maxilla, anteroinferiorly; by the perpendicular plate of the palatine bone and medial plate of the pterygoid process of the sphenoid bone posteriorly; superiorly by the labyrinth of the ethmoid bone (which separates the nasal cavity from the orbit) and medial surface of the lacrimal bone and inferiorly by the inferior nasal concha. The lateral wall contains three projections of variable size called the inferior, middle and superior nasal conchae. The inferior nasal concha is independent bone which articulates with the nasal surface of the maxilla and the perpendicular plate of the palatine bone. It is the largest nasal concha and extends along almost all the lateral nasal wall. The middle and superior nasal conchae are medial processes of the ethmoidal labyrinth. Inferolateral surfaces of the superior, middle and inferior nasal conchae form with lateral nasal wall superior, middle and inferior nasal meatuses. The part of the nasal cavity between the superomedial surfaces of the three nasal conchae and the nasal septum is common nasal meatus and the part of the nasal cavity behind the nasal conchae and the posterior opening of the nasal cavity is nasopharyngeal meatus. The posterior nasal apertures or choanae are oval openings separated by the posterior border of the vomer. Each choana is limited below by the horizontal plate of the palatine bone, above by the body of the sphenoid and laterally by the medial pterygoid plate. The anterior nasal aperture or piriform aperture is formed in its larger inferior and lateral parts by the maxillae and the nasal bones above. ORBIT The upper part of the facial skeleton contains two orbital cavities. Each cavity is pyramidal in shape and has a base at the orbital opening and long, posteromedially directed axis. The major structures which occupy the orbital cavity are eye and optic nerve, the extraocular muscles, blood vessels and nerves and lacrimal apparatus. Each orbit has four walls, the roof or superior wall, floor or inferior wall, medial and lateral walls, a base and the apex. Roof The roof or the superior wall is formed chiefly by the thin orbital plate of the frontal bone with small contribution from the sphenoid bone. Posteriorly, the lesser wing of the sphenoid bone completes the roof. It is gently concave at its orbital surface, which separates the orbital contents and the brain in the anterior cranial fossa. Anteromedially it bears a small trochlear fovea or spine where the trochlea for superior oblique is attached. Anterolaterally there is a shallow lacrimal fossa for the orbital part of the lacrimal gland. Floor The floor or inferior wall is mostly formed by the maxilla and, anteriorlly, by the zygomatic bone. Posteromedially the small triangular orbital process of the palatine bone joints the medial wall. The floor is thin and largely roofs the maxillary sinus. Not quite horizontal, it ascends a little laterally. Posteriorly it is separated from the lateral wall by the inferior orbital fissure, which connects the orbit posteriorly to the pterygopalatine fossa, and more anteriorly to the infratemporal fossa. From the posterior border of the floor of the orbit runs forwards the infraorbital groove and continues into the infraorbital canal which opens on the face at the infraorbital foramen. Lateral wall The lateral wall is formed by the orbital surface of the greater wing of the sphenoid posteriorly and by the frontal process of the zygomatic bone anteriorly. The lateral wall is the thickest wall of the orbit, especially posteriorly where it separates the orbit from the middle cranial fossa. Anteriorly the lateral wall separates the orbit and the temporal fossa. The lateral wall and the roof are separated posteriorly by the superior orbital fissure. The superior orbital fissure connects orbit with middle cranial fossa. Medial wall The medial wall of the orbit is extremely thin except posteriorly. It consists of four bones: the maxilla, lacrimal, ethmoid and sphenoid bones. Anteriorly is frontal process of the maxilla. Behind it is lacrimal bone. The largest part of the medial wall is formed by orbital plate of the ethmoid bone, and posteriorly is the body of the sphenoid bone. The anterior part of the medial wall bears the fossa for the lacrimal sac formed by lacrimal grooves on the frontal process of maxilla and lateral surface of the lacrimal bone. The fossa for the lacrimal sac is limited anteroirly by the anteiror lacrimal crest on the frontal process and posteriorly by the posterior lacrimal crest on the lacrimal bone. The fossa for the lacrimal sac continues below into the nasolacrimal duct. The orbital plate of the ethmoid bone articulates above with the frontal bone at a suture which is interrupted by anterior and posterior ethmoidal foramina which connect orbit with anterior cranial fossa. Orbiral opening The orbital opening or base of the orbit is quadrangular in shape with rounded angles. On the orbital opening there is the orbital margin formed by four margins: supra-orbital margin on the frontal bone, medial margin, the anterior lacrimal crest on the frontal process of the maxilla, infra-orbital margin on the maxilla and on the zygomatic bone, and lateral margin on the frontal process of the zygomatic bone and zygomatic process of the frontal bone. Apex The apex of the orbit lies near the medial end of the superior orbital fissure and contains the optic canal. The optic canal lies between the roots of the lesser wing of the sphenoid and is bounded medially by the body of the sphenoid. NEONATAL CRANIUM – FONTANELLES The many bones of the head collectively form the skull. Most of these bones are interconnected by sutures, which are immovable fibrous joints. In the fetus and newborn there are large membranous and unossified gaps, fontanelles between the bones of the skull, particulary between the large flat bones that cover the top of the cranial cavity. The fibrous membrane, forming the cranial vault before ossification, is unossified at the angles of the parietal bones, leaving six fonticulli (fontanelles), two median (anterior and posterior) and two lateral pairs (sphenoidal and mastoid). The anterior fontanelle, the largest, at the junction of the sagittal, coronal and frontal sutures, and hence rhomboid in shape, is 4 cm in anteroposterior and 2,5 cm in transverse dimensions. The posterior fontanelle, at the junction of the sagittal and lambdoid sutures, is hence triangular. The sphenoidal (anterolateral) and mastoid (posterolateral) fontanelles are small, irregular and at the sphenoidal and mastoid angles of the parietal bones. The fontanelles allow the head to deform during its passage through the birth canal, and to allow the postnatal growth. Fontanelles and the width of the sutures allow bones of the cranial vault some overlap. The skull is compressed in one plane with compensatory elongation orthogonal to this. These disappear within the first week. At birth the skull is larger in proportion to other skeletal parts, but the facial region is relatively small compared with its size in the adult life. Smallness of the face at birth is due to the rudimentary stage of the mandible and maxillae, non-eruption of the teeth and the small size of the maxillary sinuses and nasal cavity. The large size of the calvaria, especially the cranial vault, is related to precocious cerebral growth. Growth of the vault is rapid during the first year and then slower to the seventh by which time it has reached almost adult dimensions. Most of the fontanelles close during the first year of life by ossification of the bones around them. The sphenoidal and posterior fontanelles are closed within 2 or 3 months of birth. Mastoid fontanelles are closed usually near the end of the first year and the anterior fontanelle at about the middle of the second year.  OUTLINE General vertebral features Cervical vertebrae Craniovertebral joints GENERAL VERTEBRAL FEATURES A vertebra has a ventral body and a dorsal vertebral (neural) arch, together enclosing a vertebral foramen, occupied by the spinal cord, meninges and their vessels. Opposed surfaces of adjacent bodies are bound together by intervertebral discs of fibrocartilage. The foramina form a vertebral canal for the spinal cord and between vertebral bodies, intervertebral foramina. The cylindroid vertebral body varies in size, shape and proportions in different regions. The vertebral arch has on each side a narrower ventral part, the pedicle and dorsally a broader lamina. Projecting from their junctions are paired, superior and inferior articular processes; dorsally is a median spinous process. Pedicles are short and thick. The upper (superior) and lower (inferior) border, of the pedicle are concave and form a superior shallow and an inferior deep notch. Adjacent vertebral notches contribute to an intervertebral foramen when. Laminae, directly continuous with pedicles are vertically flattened. The spinous process (spine) projects dorsally from the junction of the laminae. Spines vary much in size, shape and direction. The superior and inferior articular processes (zygapophyses) arise from the vertebral arch at the pediculolaminar junctions. Articular processes of adjoining vertebrae thus form small synovial zygapophyseal joints. Transverse processes project laterally from the pediculolaminar junctions. Vertebrae are internally trabecular with an external shell of compact bone perforated by vascular foramina. All vertebrae, from second cervical to first sacral, articulate by cartilaginous joints between their bodies, synovial joints between their articular processes and fibrous joints between their laminae and also between their transverse and spinous processes. CERVICAL VERTEBRAE The seven cervical vertebrae, the smallest of the movable vertebrae, are typified by a foramen in each transverse process. The first, second and seventh have special features. Typical cervical vertebra The typical cervical vertebra has a small, vertebral body. The superior surface of the vertebral body is saddle-shaped, formed by flange-like lips which arise from most of the lateral circumference of the upper margin of the vertebral body; these are sometimes referred to as uncinate or neurocentral lips or processes. The pedicles and the longer laminae, enclosing a large, triangular vertebral foramen. The spinous process of the sixth cervical vertebra is larger and is often not bifid. The spinous process (spine) is short and bifid, with two tubercles. The junction between lamina and pedicle bulges laterally between the superior and inferior articular processes. The transverse process is morphologically composite around the foramen transversarium. Its dorsal and ventral roots terminate laterally as corresponding tubercles. Anterior tubercles of the transverse process of the fourth to sixth cervical verterbrae are elongated and rough for tendinous slips of scalenus anterior; the sixth is the longest and is often called the carotid tubercle. The carotid artery can be immobilized and compressed in the groove formed by the vertebral bodies and the larger anterior tubercles. Atlas The atlas, the first cervical vertebra, supports, the head. The atlas consists of two lateral masses connected by a short anterior and a longer posterior arch. The anterior arch is convex anteriorly, and carries a roughened anterior tubercle. Its upper and lower borders provide attachment to the anterior atlanto-ocipital membrane. The posterior surface of the anterior arch carries a concave, facet for the dens. The lateral masses are ovoid; their long axes converging anteriorly. Each bears a reniform superior articular facet for the respective occipital condyle. On the medial surface of each lateral mass is a tubercle for attachment of the transverse ligament. On the posterior arch the superior surface bears a wide groove for the vertebral artery. The posterior tubercle of the posterior arch is a rudimentary spinous process.  The transverse processes are longer than those of all cervical vertebrae except the seventh. The apex of the transverse process, which is usually palpable between the mastoid process and ramus of the mandible is homologous with the posterior tubercle of typical cervical vertebrae. Axis The axis, the second cervical vertebra, has a dens (odontoid process), which projects cranially from the superior surface of the body. The dens is conical in shape, with a length of 15.0 mm. The anterior surface bears an ovoid articular facet for the anterior arch of the atlas. Large ovoid articular facets are present on either side of the dens. Seventh cervical vertebra The seventh cervical vertebra, or „vertebra prominens“, has a long spinous process visible at the lower end of the nuchal furrow. CRANIOVERTEBRAL JOINTS The articulation between the cranium and vertebral column consists of the occipital condyles, atlas and axis and functions like a universal joint. 1. Atlanto-occipital joints Each joint consists of two articular surfaces, one on the occipital condyle the other on the lateral mass of the atlas. The bones are connected by articular capsules and the anterior and posterior atlanto-occipital membranes. The anterior atlanto-occipital membrane connects the anterior margin of the foramen magnum to the upper border of the anterior arch of the atlas. The posterior atlanto-occipital membrane is also broad, but relatively thin, connecting the posterior margin of the foramen magnum to the upper border of the posterior atlantal arch. It arches over the grooves for the vertebral arteries, venous plexuses and first cervical nerve. The main movement at the atlanto-occipital joints is flexion, with a little lateral flexion and rotation. 2. Atlanto-axial joints Articulation of atlas to axis is at three synovial joints, a pair between lateral masses (lateral atlantoaxial joints), and a median complex between the dens of the axis and the anterior arch and transverse ligament of the atlas (median atlantoaxial joint). Median atlantoaxial joint is a pivot between the dens and a ring formed by the anterior arch and transverse ligament of the atlas. It has two synovial cavities which sometimes communicate. A ovoid facet on the anterior dens articulates with the one on the posterior aspect of the anterior atlantal arach. The synovial cavity of the posterior component of the median joint complex lies between the posterior surface of the dens and the cartilaginous anterior surface of the transverse ligament. The transverse ligament divides the ring of the atlas into unequal parts; the posterior and larger surrounds the spinal cord and meninges, the anterior contains the dens. The transverse atlantal ligament is a broad, strong band. It is attached laterally to a small but prominent tubercle on the medial side of each atlantal lateral mass. From its upper margin a strong median longitudinal band arises which inserts into the basilar part of the occipital bone, and from its interior surface a weaker consistent longitudinal band passes to the posterior surface of the axis. These transverse and longitudinal components together constitute the cruciform ligament. Movements at the atlantoaxial joints are simultaneous at all three joints and consist almost exclusively of rotation of the axis. 3. Ligaments connecting axis and occipital bone Ligaments of the craniovertebral joints consist of the membrana tectoria, and paired alar and median apical ligaments. Membrana tectoria is placed inside the vertebral canal. This is a strong band representing the upward continuation of the posterior longitudinal ligament. Membrana tectoria is attached to the posterior surface of the axial body, attaching above the foramen magnum. Alar ligaments are thick cords that extend from the apex of the dens horizontally and laterally to the occipital condyles. Apical ligament of the dens fans out from the apex of the dens into the anterior margin of the foramen magnum between the alar ligaments. Ligamentum nuchae also connects cervical vertebrae with the cranium. This is a bilaminar fibroelastic intermuscular septum often considered homologous supraspinous and interspinous ligaments in the neck. Extends from the external occipital protuberance to the spine of C7.  OUTLINE Temporomandibular joint Muscles and fasciae of the head JOINTS OF THE HEAD There are three types of the joint of the head: fibrous joints, cartilagineous joints and synovial joints. Fibrous joints are: sutures and dento-alveolar syndesmoses. Sutures are junctions between adjacent bones of the skull. They are rigidly held together by fibrous connective tissue. The major sutures are: coronal suture (between the frontal and parietal bones), sagittal suture (between the right and left parietal bones), squamous suture (between squamous part of the temporal bone and parietal bone), lambdoid suture (between occipital and parietal bones). Other sutures are: sphenosquamous suture, occipitomastoid suture, sphenofrontal suture, sphenoparietal suture, parietomastoid suture. Dento-aveolar syndesmoses (gomphoses, or gompholitic joints) are fibrous joints by which the root of a tooth is fixed into the dental alveoli or sockets of the alveolar part of the mandible or maxilla by the periodontal ligaments or periodontium. Cartilagineous joints (synchondroses) are the cartilagineous junctions betweeen the bones of the cranium. The synchondroses occur within the developing chondrocranium forming early support for the rapidly developing brain. They occur between the bones forming the base of the skull (occipital, temporal, sphenoidal and ethmoidal bones): sphenoethmoidal synchondrosis, sphenooccipital synchondrosis, sphenopetrosal synchondrosis, petrooccipital synchondrosis... Synovial joints of the head are temporomandibular and atlanto-occipital joint. TEMPOROMANDIBULAR JOINT (TMJ) The temporomandibular joint is a bilateral synovial articulation between the mandible and temporal bone. The name of the joint is derived from the names of bones which form the joint. Each joint involves the temporal articular tubercle and anterior part of the mandibular fossa above and mandibular condyle below. An articular disc completely divides the joint, into upper and lower parts. Articular disc is oval in shape and it is composed of dense fibrous connective tissue. It has central depression in its lower surface that accommodates the articular surface of the mandibular condyle. Its edges are fused with the fibrous capsule. Its function is to stabilize the TMJ. It is like a cushion. The position of the disc is controlled by muscle function. The major ligament associated with the TMJ is the lateral ligament. It is a strong and broad ligament within the lateral part of the fibrous capsule (it is woven into the capsule). It is attached to the articular tubercle and extends downwards and backwards to the lateral surface of the neck of the mandible. It prevents posterior displacement of the condyle of the mandible. There are also some distant ligaments that are important in restriction of excessive movements in the joint (especially in excessive opening of the mouth). Sphenomandibular ligament is medial; it descends from the spine of the sphenoidal bone and merges to the lingula of the mandibular foramen. Stylomandibular ligament is a specialized band of deep cervical fascia wich streches from the apex of styloid process to the mandible’s angle.  During jaw movements, only the mandible moves. Normal movements of the mandible during function, such as mastication, or chewing, are known as excursions: depression of mandible (opening of the mouth), elevation of mandible (closing the mouth), two lateral excursions (left and right), known as diduction, the forward excursion, known as protrusion, and the reversal of protrusion, known as retrusion or retraction. ATLANTO-OCCIPITAL JOINT Joint consists of two articular surfaces, one on the occipital condyle the other on the lateral mass of the atlas. The bones are connected by articular capsules and the anterior and posterior atlanto-occipital membranes. The anterior atlanto-occipital membrane connects the anterior margin of the foramen magnum to the upper border of the anterior arch of the atlas. The posterior atlanto-occipital membrane is also broad, but relatively thin, connecting the posterior margin of the foramen magnum to the upper border of the posterior atlantal arch. It arches over the grooves for the vertebral arteries, venous plexuses and first cervical nerve. The main movement at the atlanto-occipital joint is flexion, extention, with a little lateral flexion. MUSCLES AND FASCIAE OF THE HEAD Muscles of the head are divided into two groups Superficial (craniofacial or mimetic) muscles Deep (masticatory) muscles are concerned primarily with movements of the temporomandibular joint This division of head musculature reflects differences in embryonic origin and innervation. In functional terms, activities such as mastication, deglutition, vocalization, communicative and emotional expression, respiration, ocular, aural and nasal action brought about by close co-operation and interdependence between muscles of the two groups. I. CRANIOFACIAL MUSCLES (muscles of the face or muscles of facial expression). Craniofacial myology is structurally and functionally very complex. The muscles of the face are embedded in the superfical fascia and the majority arise from the bones of the skull and are inserted into the skin. The orifices of the face, namely, the orbit, nose and mouth are guarded by the eyelids, nostrils and lips. Craniofacial muscles surround these openings and serve as sphincters or dilators of these structures. A secondary function of the facial muscles is to modify the expression of the face. All the muscles of the face are supplied by the facial nerve. Craniofacial muscles are grouped topographically and functionally as: Epicranial Epicranial group consists of occipitofrontalis and temporoparietalis muscles. Occipitofrontalis covers the dome of the skull from the eyebrows to the highest nuchal line. It has occipital and frontal part connected by the epicranial aponeurosis. Occipital part arises from the highest nuchal line, while frontal part has no bony attachments of its own. Acting from the above, frontal part raise eyebrows and skin over the root of the nose (expressions of surprise or horror). Acting from the below it draws the skalp forwards, throwing the forehead into transverse wrinkles. Occipital part draws the skalp backwards. Temporoparietalis muscle is variable developed muscle which lies between the frontal parts of occipitofrontalis and the anterior and superior auricular muscles. Circumorbital and palpebral The circumorbital and palpebral group of muscles are the muscles that surrounds orbit and form the lids. These muscles are: orbicularis oculi, corrugator supercilli and levator palpebrae superioris (which belongs to the lids). Orbicularis oculi is a broad, flat and elliptical muscle which surrounds the circumference of the orbit. It is a sphincter muscle and plays important role in the facial expression and ocular reflexes. It closes the lids voluntarily or reflexly (to close the lids protectively in blinking), and helps drainage of tears. When contracts it produces the skinfolds which radiate from the lateral angle of the eyelids (they become permanent in middle age). Corrugator supercilii is a small muscle located at the medial end of each eyebrow. It cooperates with orbicularis oculi, drawing the eyebrows medially and downwards. It is also involved in frowning. Nasal Nasal muscle group comprises procerus, nasalis and depressor septi. Procerus is a small pyramidal slip close to (or blended with) the occipitofrontalis muscle. It is inserted into the skin between the eyebrows. It produces transverse wrinkles over the bridge of the nose in frowning and “concentration”. Nasalis covers the lateral parts of the nose and assists in widening the anterior nasal aperture. Depressor septi arises above the incisors and ascends to attach to the nasal septum. It pulls the septum downwards and widens the nasal aperture. Buccolabial Buccolabial group is the largest. The most important muscle in this group is the buccinators. It is the muscle of the cheek and the only one which has a fascia. It occupies the interval between the maxilla and mandible. It attaches to the alveolar processes of the maxilla and mandible and the anterior margin of the pterygomandibular raphe. It compresses the cheek against the teeth anf gums during mastication and assist the tongue in directing the food between the teeth. When the cheeks have been distended with air, the buccinator expel it between the lips (activity important when playing wind instruments). Other buccolabial muscles are: levator labii superioris (starts from the infraorbital margin and ends on the uper lip; it elevates and everts upper lip), levator labii superioris alaeque nasi (arises from the upper part of the frontal process of maxilla and inserts into an greater alar cartilage of the nose and the upper lip; it raises and everts upper lip), zygomaticus muscles (arise from zygomatic bone and pass to the angle of the mouth; they draw the angle upwards and laterally in laughing and elevate upper lip in expressing smugness and contempt), risorius (known as „a muscle of laughing“; it is variable; it arises from the zygomatic arch and ends on the dense, fibromuscular mass on each side of the face), depressor anguli oris (it has the origin from the mental tubercle and ends at the angle of the mouth; it draws the angle of the mouth downwards and laterally expressing the sadnesss), depressor labii inferioris (arises from the oblique line of the mandible and ends at the lower lip; it draws the lower lip downwards and little laterally in expression of melancholy, sorrow and doubt), orbicularis oris (surrounds the mouth like an ellipse) and mentalis (arises from the incisive fossa on the mandible and attaches to the skin of the chin; it raises the lower lip, wrinkling the skinnof the chin). II. MASTICATORY MUSCLES The masticatory muscles are most immediately concerned with the movements of the mandible in mastication (and speech). One side of the masticatory muscles is attached to the mandible. All masticatory muscles are innervated by mandibular nerve. There are four masticatory muscles: masseter, temporalis, and medial and lateral pterygoid muscles. Temporalis Temporalis arises from the whole of the temporal fossa up to the inferior temporal line and from the deep surface of the temporal fascia. Its fibres converge and descend into a tendon which passes through the gap between the zygomatic arch and the side of the skull. The muscle attaches to the medial surface, apex, anterior and posterior borders of the coronoid process and to the anterior border of the mandibular ramus. The anterior fibres of temporalis are orientated vertically, the most posterior fibres almost horizontally. Temporalis elevates the mandible and so closes the mouth. It also contributes to side-to-side grinding movements. The posterior fibers retract the mandible after it has been protruded.  The nerve supply is provided by the branches of the mandibular nerve. Masseter Masseter is a quadrilateral muscle consisting of three layers which blend anteriorly. The superficial layer is the largest: it arises by a thick aponeurosis from the zygomatic bone and from the anterior two-thirds of the inferior border of the zygomatic arch. Fibres pass downwards and backwards, to insert into the angle and lateral surface of the mandibular ramus. The middle layer arises from the medial aspect of the anterior two-thirds of the zygomatic arch and from the lower border of the posterior third of the arch, and inserts into the central part of the mandibular ramus. The deep layer arises from the deep surface of the zygomatic arch and inserts into the upper part of the mandibular ramus and into its coronoid process. Because it is so close to the skin, the masseter is easily palpated when it contracts. Masseter elevates the mandible to occlude the teeth in mastication and has small effect in side-to-side movements, protraction and retraction. Masseter is supplied by a branch of the mandibular nerve. Lateral pterygoid Lateral pterygoid is a short, thick muscle consisting of two heads - upper and lower one. Upper head arises from the infratemporal surface and infratemporal crest of the greater wing of the sphenoid bone, while lower head arises from the lateral surface of the lateral pterygoid plate. The fibers of the lateral pterygoid converge and pass backwards and laterally to be inserted into the pterygoid fovea. A part of the upper head may be attached to the capsule of the temporomandibular joint. Lateral pterygoid assists in opening the mouth (digastric and geniohyoid are the main jaw opening muscles). When right and left muscles contract together the condyle is pulled forward and slightly downward producing protrusion and depression of the mandible Lateral pterygoid muscle is innervated by the branch from the mandibular nerve. Medial pterygoid Medial pterygoid is a thick, quadrilateral muscle with the deep origin from the medial surface of the lateral pterygoid plate of the sphenoid bone (pterygoid fossa), and superficial origin from the maxillary tuberosity and the pyramidal process of the palatine bone. Its fibres descend and are attached by a strong tendinous lamina to the medial surfaces of the mandibular ramus and angle. Medial pterygoid muscle is suppled by the branch from the mandibular nerve. It assists in elevating the mandible and protracts the mandible (acting with the lateral pterygoid). FASCIAE OF THE HEAD Temporal fascia The temporal fascia that covers temporalis is a strong aponeurosis overlapped. The superficial temporal vessels and the auriculotemporal nerve ascend over it. Above, it is a single layer, attached to the whole of the superior temporal line; below, it has two layers, one attached to the lateral and the other to the medial margin of the superficial temporal artery. The deep surface of the fascia affords attachment to the superficial fibres of temporalis. Masseteric fascia The masseteric fascia is continuous with the temporal fascia on the zygomatic arch and then passes downwards. Posteriorly it is attached to the cartilage of the external acoustic meatus and passes over to the mastoid process. Inferiorly it is continuous with the cervical fascia; anteriorly it covers the masseter after which it is continuous with the buccopharyngeal fascia. Parotid fascia The parotid fascia is a strong layer of fascia, derived from the deep cervical fascia. It is attached to the lower border of the zygomatic arch and invests the parotid gland. Buccopharyngeal fascia The buccopharyngeal fascia covers the buccinator muscle and at the anterior border of the masseteric muscle, passes over to the medial surface of the mandibular ramus where it covers the medial pterygoid muscle and then stretches over to the pharyngeal wall.  OUTLINE Blood vessels of the head and neck CAROTID SYSTEM OF ARTERIES The common carotid artery is a large bilateral vessel supplying head and neck; it ascends to the level of the thyroid cartilage`s upper border, where it divides into an external carotid, supplying the head, face and most of the neck, and an internal carotid, supplying the cranial and orbital contents. COMMON CAROTID ARTERIES The right and left carotid arteries differ in length and origin. The right carotid, originates from the brachiocephalic trunk behind the right sternoclavicular joint. The left carotid originates directly from the aortic arch and therefore has both, thoracic and cervical parts. Thoracic part of the left common carotid artery ascends until the level of the left sternoclavicular joint, where it enters the neck. It is 20-25 mm long and it lies at first in front of the trachea, then it inclines to the left. Cervical part of both common carotid arteries ascends, diverging laterally from behind the sternoclavicular joint to the thyroid cartilage`s upper border, where it divides into external and internal carotid arteries. At its division the vessel has a dilatation, the carotid sinus. The sinus is responsive to changes in arterial blood pressure, leading to reflex hemodynamic modification. Its position on the main artery of the brain accounts for its role as a baroreceptor in the control of intracranial pressure. The carotid body, behind the common carotid bifurcation, a small, reddish-brown structure is a `chemoreceptor`. Each common carotid is contained in a carotid sheath, continuous with the deep cervical fascia. This sheath encloses also the internal jugular vein and vagus nerve; the vein lies lateral to the artery, the nerve between them and posterior to both. EXTERNAL CAROTID ARTERY This artery begins lateral to the thyroid cartilage`s upper border. It first ascends between the mastoid tip and the mandibular angle. Behind the mandible`s neck, in the substance of the parotid gland, it divides into the superficial temporal and maxillary arteries. At its origin, it is anteromedial to the internal carotid but becomes anterior, than lateral to this as it ascends. At mandibular levels the styloid process and its attached structures intervene between the vessels, the internal carotid being deep and the external superficial to the styloid process. First part of the external carotid artery is placed in the carotid triangle and it is covered by superficial fascia and skin. Leaving the carotid triangle, it is crossed by the posterior belly of digastrics and by stylohyoid muscle. It enters the parotid gland where it is placed medial to the facial nerve and the junction of the superficial temporal and maxillary veins. External carotid artery gives eight branches (superficial temporal and maxillary artery are terminal branches): 1. Superior thyroid 2. Ascending pharyngeal 3. Lingual 4. Facial 5. Occipital 6. Posterior auricular 7. Superficial temporal 8. Maxillary 1. SUPERIOR THYROID ARTERY  This arises from the anterior surface of the external carotid artery dividing into terminal branches at the apex of the thyroid lobe. It supplies the thyroid gland and adjacent skin. 2. ASCENDING PHARYNGEAL ARTERY This, the smallest branch of the external carotid, is a long vessel, arising posteriorly near the external carotid`s origin and ascending to the cranial base. It supplies muscles of the pharynx, palatine tonsil, middle ear and meninges. 3. LINGUAL ARTERY Lingual artery provides the chief blood supply to the tongue and the floor of the mouth. It often arises with the facial or, less often, with the superior thyroid artery. It arises anteromedially from the external carotid ascending almost vertically, courses sinuously forwards on the tongues inferior surface as far as its tip. Its relationship to hyoglossus divides the lingual artery into “thirds”: first part is in the carotid triangle; second part passes deep to hyoglossus, the lower part of the submandibular gland and the posteror part of mylohyoid; third part is the arteria profunda linguae which turns upward near the anterior border of hyoglossus and then passes forwards close to the inferior lingual surface, accompanied by the lingual nerve. Branches are suprahyoid, dorsal lingual arteries and sublingual artery. 4. FACIAL ARTERY This artery, arises anteriorly from the external carotid artery in the carotid triangle above the lingual artery. Reaching the surface of the mandible it curves round its inferior border, anterior to the masseter, to enter the face. Here it ascends sinuously and ends at the medial palpebral commissure where it joins the dorsal nasal branch of the ophthalmic artery. Terminal part of the facial artery is termed the angular artery. Facial artery gives several branches: ascending palatine artery (supplies pharynx and tonsils), tonsillar artery (supplies palatine tonsils and the tongue), superior and inferior labial arteries (supply the structures of the upper and lower lip) and submental artery. 5. OCCIPITAL ARTERY This artery arises posteriorly from the external carotid, about 2 cm from its origin. It runs in the occipital groove of the temporal bone and ends posteriorly in the scalp. 6. POSTERIOR AURICULAR ARTERY Posterior auricular artery is a small vessel which branches posteriorly from the external carotid artery. It ascends to the groove between the auricular cartilage and mastoid process and divides into auricular and occipital branches. 7. SUPERFICIAL TEMPORAL ARTERY This, the smaller terminal branch of the external carotid, begins in the parotid gland behind the mandible`s neck, crosses the posterior root of the zygomatic process of the temporal bone and this divides into anterior and posterior branches.  The superficial temporal supplies the parotid gland, temporomandibular joint and masseter and it also has several named branches (transverse facial, auricular, zygomatico-orbital, middle temporal, frontal and parietal arteries). 8. MAXILLARY ARTERY This, the larger terminal branch of the external carotid artery. It arises behind the mandibular neck, at first embedded in the parotid gland; it then passes medial to the mandibular neck and superficial or deep to the lower head of the lateral pterygoid to reach the pterygopalatine fossa. Its terminal part (sphenopalatine artery) traverses sphenopalatine foramen end enters the nasal cavity. It has mandibular, pterygoid and pterygopalatine segments. The first, mandibular, part is horizontal and passes between the mandible`s neck and the sphenomandibular ligament. The second, pterygoid, part ascends obliquely forwards superficial or deep to the lateral pterygoid. The third, pterygopalatine, part passes through the pterygomaxillary fissure into the pterygopalatine fossa, where it is situated anterior to the pterygopalatine ganglion. The artery supplies mandible, maxilla, teeth, muscles of mastication, palate, nose and cranial dura mater. Its branches are organized into three groups, corresponding with its parts. Branches of the first part Deep auricular artery pierces the wall of the external acoustic meatus, and supplies its skin and the outer surface of the tympanic membrane. Anterior tympanic artery is a small artery that supplies the middle ear. It enters the tympanic cavity through the petrotympanic fissure, and ramifies upon the tympanic membrane. Middle meningeal artery is the largest of the meningeal arteries. It enters the cranial cavity through the foramen spinosum. It then runs in a groove on the squamous part of the temporal bone, dividing into frontal and parietal branches. Inferior alveolar (dental) artery descends to the mandibular foramen. Before entering the foramen it has a mylohyoid branch, which descends with the mylohyoid nerve in its groove on the mandibular ramus. The inferior alveolar artery then traverses the mandibular canal with the inferior alveolar nerve and divides into the incisor and mental branches near the first premolar. The incisor branch continues to the midline, where it anastomoses with its fellow. The mental branch leaves the mental foramen, supplies the chin and anastomoses with the submental and inferior labial arteries. Branches of the second part Branches of the second part are muscular branches for the masticatory and craniofacial muscles (deep temporal branches, pterygoid branches, masseteric artery, buccal artery). Branches of the third part Posterior superior alveolar (dental) artery leaves the maxillary artery as it eaters the pterygopalatine fossa. It descends on the maxilla`s infratemporal surface. It divides into numerous branches, some of which enter the alveolar canals, to supply the molar and premolar teeth and the lining of the maxillary sinus, while others are continued forward on the alveolar process to supply the gingiva. Infraorbital artery enters the orbit posteriorly through the inferior orbital fissure, to run in the infraorbital groove and canal with the infraorbital nerve, both emerging on the face via the infraorbital foramen. It supplies the upper incisor and canine teeth and the mucous membrane of the maxillary sinus. Greater (or descending) palatine artery descends in their palatine canal. The artery gives off two or three lesser palatine arteries. The main vessel emerges on the palate’s oral surface by the greater palatine foramen and runs in a curved groove near the alveolar border of the hard palate to the incisive canal: it ascends this canal and anastomoses with a branch of the sphenopalatine artery. It supplies the gingivae, palatine glands and mucous membrane. Artery of the pterygoid canal passes through the pterygoid canal and supplies the upper part of the pharynx, auditory tube,