Anatomy of The Skull PDF

THE SKULL( II) DR.FAHD AL-AMODI LECT.2 HSC(OMFS),BDS 01/10/2023  III- THE NORMA FRONTALIS It is the anterior aspect of the skull.  CONTINUE… * Bones forming i...

THE SKULL( II) DR.FAHD AL-AMODI LECT.2 HSC(OMFS),BDS 01/10/2023  III- THE NORMA FRONTALIS It is the anterior aspect of the skull.  CONTINUE… * Bones forming it: frontal bone, 2 zygomatic bones, 2 maxillary bones (uniting to form the upper jaw) & the mandible (lower jaw). Sutures between the bones: (1) Metopic suture: between the 2 halves of the frontal bone (present in 9% of people only). (2) Frontonasal suture. (3) Frontomaxillary suture. (4) Zygomaticomaxillary suture. (5) intermaxillary suture * Parts of the norma frontalis: (1) Upper part or forehead: formed by the frontal bone. (2) Middle part: containing the 3 cavities: 2 orbital cavities & nasal cavity. (3) Lower part: formed by the upper & lower jaws. * Special Features:  CONTINUE… (1) Frontal eminences: the most prominent areas on either side of the forehead. (2) Superciliary arches: elevated arched ridges just above the medial parts of the sup. orbital margins. They are more prominent in males. (3) Glabella: a median elevation between the 2 superciliary arches above the root of nose. (4) Nasion: the point of meeting of frontonasal & internasal sutures. (5) Supra-orbital notch (or foramen): lies at the junctiorn of the med. 1/3 & lat. 2/3 of the sup. orbital margin. It transmits supra orbital nerve & vessels. (6) the nasal bones: they form the bridge of the nose. They articulate above with the frontal bone (frontonasal suture), laterally, with the frontal process of maxilla. They articulate together in the middle line (internasal suture). Their lower borders form the upper boundary of the ant. nasal aperture (piriform aperture)  (7) the zygomatic bones: each bone has: (a) Frontal process: articulating with the frontal bone. (b) temporal process: articulating with zygomatic process of temporal bone to form the zygomatic arch. (c) maxillary process: articulating with maxilla. (d) orbital plate: sharing in formation of the lat. wall & the floor of the orbital cavity. (e) zygomaticofacial f: close to the inferolateral angle of the orbit.  (8) The 2 Maxillary bones: - they articulate together in the median plane forming the upper jaw & form a large share of the facial skeleton. - each maxillary bone has: (a) body containing the maxillary air sinus. (b) frontal process: articulates with the Frontal bone (above), with nasal bone (anteriorly) & with lacrimal bone (posteriorly). (c) anterior surface showing: (1) nasal notch: medially sharing in the ant. nasal aperture. (2) ant. nasal spine: is a median projection at the lower border of the ant. nasal aperture.  CONTINUE… (3) canine eminence: a projection produced by the root of canine tooth. (4) canine fossa: a shallow depression lat. to the canine eminence. (5) incisor fossa: a shallow depression med. to the canine eminence (above the incisor teeth). (d) Alveolar process: carrying 8 teeth (16 in both maxillae) arranged as follows: (counting from the middle line backwards): (1, 2) 2 incisors: med. & lat. (3) canine tooth. (4, 5) 2 premolars. (6, 7 & 8) 3 molars. (e) Zygomatic process: articulates with the maxillary process of the zygomatic bone. Orbital openings:  (9) Orbital openings: each opening is quadrangular having 4 margins: (a) supra-orbital margin: formed by the frontal bone. (b) infra-orbital margin: formed by zygomatic bone laterally + maxillary bone medially. (c) lat. orbital margin: formed by frontal process of zygomatic bone +zygomatic process of frontal bone. (d) med. orbital margin: formed by frontal bone (above) + frontal process of maxilla (below) (10) Anterior nasal (Piriform) aperture: - it is pear-shaped & bounded by: - above: by the lower borders of the nasal bones. - below: by the nasal notch of maxilla on each side.  (11) Foramina in norma frontalis include: (a) supra-orbital notch or foramen (b) infra-orbital foramen (c) mental foramen (d) zygomaticofacial f.: in the zygomatic bone (in male) zygomaticofacial nerve & vessels. N.B: (A,B AND C)lie along a vertical line passing between the 2 premolar teeth & transmit nerves and vessels indicated by their names (terminal brs. of trigeminal n.) IV- THE NORMA LATERALIS  Bones forming it: - Superiorly: nasal, frontal & parietal bones. - inferiorly: maxilla, zygomatic, greater wing of sphenoid, squamous & mastoid parts of temporal bone & squamous part of the occipital bone.  Special Features (1) Temporal line(s): strata anteriorly at the zygomatic process of the frontal bone. It soon divides into: (a) superior temporal line: fades away as it passes backwards. It gives attachment to: (a) epicranial aponeurosis (b) temporal fascia. (b) inferior temporal line: curves backwards then downwards & forwards to become continuous with the supramastoid crest. It gives origin to: temporalis muscle. (2) Supramastoid crest: it is the distinct lower end of the temporal line as it passes above the mastoid process to reach the post. end of the zygomatic process of temporal bone. (3) Zygomatic arch: it is a bony bridge formed of: (a) the temporal process of the zygomatic bone (anteriorly) & (b) the zygomatic process of the temporal bone (posteriorly). - Its lower border & inner surface give origin to the masseter m.  Parts of Norma lateralis: --supratemporal area. temporal fossa. Infratemporal fossa. Stylomastoid region. (1) the supratemporal area: It lies between the middle line & the temporal line. It is covered by scalp. (2) the temporal fossa: - Boundaries: a) sup. temporal line --------------------------------------- above & behind. b) zygomatic arch -------------------------------------------- below. c) frontal process of zygomatic bone ------------------- anteriorly. Structures attached: the 2 superficial muscles of mastication: a) temporalis m. arises from the floor of the temporal fossa. b) masseter m. arises from the lower border & inner surface of zygomatic arch. (3) Infratemporal fossa: it is the space below the temporal fossa & behind maxilla. - Boundaries: - anteriorly: post. surface of maxilla. - medially: lateral pterygoid plate. - laterally: ramus & coronoid process of mandible. - posteriorly: styloid & mastoid processes. - Communications: it communicates with: (1) orbit through the inferior orbital fissure. (2) temporal fossa through the gap deep to the zygomatic arch. (3) pterygopalatine fossa through the pterygomaxillary fissure. (4) middle cranial fossa through the foramen ovale & foramen spinosum. Contents of the infra temporal Fossa: (1) Muscles: the 2 deep muscles of mastication: (2) Ligament: the sphenomandibular lig. (3) Vessels: (a) 1st & 2nd parts of maxillary artery & their branches (b) pterygoid venous plexus & maxillary vein. (4) Nerves: (a) mandibular n. & its brs. (b) small part of maxillary n. (c) chorda tympani. (d) otic ganglion. Important landmarks:  Important landmarks: (1) Pterion: - it is the area of meeting of 4 bones connected by H-shaped suture:( forntal bone,greater wing of sphenoid,squamous part of temporal bone and parietal bone) - At birth, the pterion is occupied by a membrane called the anterolateral (sphenoidal) fontanelle which ossifies at the age of 3 months. - In the adult, the centre of the pterion lies about 1 ½ʺ behind the frontozygomatic suture & 1 ½ʺ above the midpoint of the zygomatic arch. - Importance: the center of the pterion is related internally to ant. br. of middle meningeal a. (2) Asterion: -it is the point of meeting of 3 bones: 1-pariatel bone. 2- occipital bone. 3- mastoid temporal bone. At birth, the asterion is occupied by a membrane called the posterolateral (mastoid) fontanelle which ossifies at the age of 3 months. - In the adult, the asterion is related internally to the highest point of transverse sinus. External auditory meatus: - lies just below the post. root of the zygomatic process of temporal bone. - It is bounded: a) posterosuperiorly by squamous temporal bone. b) anteroinferiorly by tympanic part of temporal bone. -its rough margin gives attachment to the cartilagenous part of the meatus. Mastoid process: - it is a nipple-like process felt subcutaneously deep to the lobule of the ear. - its outer surface gives insertion to 3 muscles arranged from before backwards as follows: (a) Sternomastoid m. (b) Splenius capitis m. (c) Longissimus capitis m. Styloid process: - it is a thin long projection from temporal bone anteromed. to mastoid pr. - its base is partly ensheathed by the tympanic plate. - It gives attachment to 2 ligaments & 3 muscles Pterygo-maxillary fissure: - it is a vertical slit between the upper parts of(1)pterygoid process posteriorly(2)maxilla anteriorly. - it leads medially into the pterygopalatine fossa (connecting it with the infratemporal fossa laterally). - its upper end is continuous with the inferior orbital fissure which leads to the orbit. - it transmits maxillary n. & maxillary a. Pterygo-palatine fossa: - it is a small inverted pyramidal-shaped space lying med. to the pterygomaxillary fissure & behind the apex of orbit. - Boundaries: - ant. wall: post. surface of maxilla. - post. wall: pterygoid process of Sphenoid bone. - med. wall: perpendicular plate of the palatine bone. - laterally: pterygomaxillary fissure communicates it with the infratemporal fossa. - Contents of the pterygopalatine fossa: (1) terminal part of maxillary artery. (2) maxillary nerve. (3) sphenopalatine ganglion suspended from the nerve. Foramina & fissures opening in the pterygopalatine fossa:  Foramina & fissures opening in the pterygopalatine fossa: In the posterior wall: (1) foramen rotundum: transmitting maxillary n. from the cranial cavity to the fossa. (2) pterygoid canal: transmitting the nerve and artery of the pterygoid canal. (3) palatovaginal canal: transmitting the pharyngeal branch of the sphenopalatine ganglion to the pharynx. - In the medial wall: (4) the sphenopalatine foramen: transmitting the short and long sphenopalatine nerves to the nasal cavity - In the anterior wall: (5) the inf. orbital fissure: connecting the fossa with the orbit. - In the apex: (meeting of the ant. & post. walls): (6) greater palatine and lesser palatine canals: transmitting the greater and lesser palatine nerve and vessels to the palate. - In the lateral wall: (7) pterygomaxillary fissure: connecting the pterygopalatine fossa to the infratemporal fossa and transmitting maxillary n. and a. THANK YOU FOR ATTENTION