Memorix Anatomy E-book PDF

2 Skull – Cranium 2 The neurocranium, or more colloquially the “brain case”, is a group of bones in the skull that encloses and protect...

2 Skull – Cranium 2 The neurocranium, or more colloquially the “brain case”, is a group of bones in the skull that encloses and protects the brain and its associated organs of vision, audition and balance. The neurocranium is divided into the cranial vault and the cranial base. The viscerocranium (facial skeleton) is a group of bones in the skull that surrounds and protects the proximal parts of the digestive and respiratory systems. Overview of the bones of the skull 1.1 1 Neurocranium – brain box or brain case 1.2 Cranial vault / calvaria 1.1 Parietal bone (os parietale) 1.2 Frontal bone (os frontale) 1.3 Occipital bone (os occipitale) 2.2 Cranial base (basis cranii) 2.1 1.4 Temporal bone (os temporale) 1.6 1.5 Sphenoid bone (os sphenoidale) 1.3 1.6 Ethmoid bone (os ethmoidale) 2.5 1.4 2 Viscerocranium – facial skeleton 2.1 Lacrimal bone (os lacrimale) 2.7 2.2 Nasal bone (os nasale) 2.3 Vomer 2.4 Inferior nasal concha (concha nasalis inferior) 2.8 2.5 Zygomatic bone (os zygomaticum) 2.9 2.6 Palatine bone (os palatinum) 2.7 Maxilla Lateral view (norma lateralis) 2.8 Mandible (mandibula) 2.9 Hyoid bone (os hyoideum) 1.1 1.2 1.2 1.6 1.2 1.5 1.5 1.6 1.4 1.4 1.5 2.1 2.2 2.5 1.6 2.6 2.4 2.7 2.3 1.1 1.1 1.3 1.3 2.8 Superior view (norma superior/verticalis) Superior view (norma superior/verticalis) Anterior view (norma facialis/frontalis) 2.6 2.7 2.5 1.2 1.5 1.1 2.3 1.3 1.4 1.4 2.6 2.7 1.1 1.1 1.3 1.3 2.8 Inferior view (norma inferior/basalis) Inferior view (norma inferior/basalis) Posterior view (norma occipitalis) This copy belongs to Devosree De 21  2.1 Frontal bone – Os frontale Bones The frontal foramen and the supra- Originally a paired bone of the cranial vault which develops by intramembranous os- orbital foramen (foramina frontalis sification, the frontal bone is an unpaired pneumatised bone and contains a paranasal et supraorbitalis) are variable open- ings which can replace the frontal sinus: the frontal sinus. The frontal bone consists of a squamous part, a nasal part and and supraorbital notch (incisura two paired orbital parts. frontalis et supraorbitalis). 1 Squamous part (squama frontalis) Gyral impressions (impressions gyr- arum) are impressions of the cere- External surface (facies externa) 1.1 Frontal tuber (tuber frontale) – paired large elevations containing ossification centers bral gyri on the inner surface of the frontal bone. The cerebral juga are 1.2 Superciliary arch (arcus superciliaris) – paired arches located above the orbits eminences between these impres- 1.3 Glabella – a flattened area above the nasal root and between the superciliary arches sions. 1.4 Supra-orbital margin (margo supraorbitalis) – the superior border of the orbit 1.4.1 Frontal notch/foramen (incisura/foramen frontale) The spheno-occipital synchondro- – a notch or foramen above the orbit that is only occasionally present sis ossifies at the age of eighteen. – transmits the medial branch of the supra-orbital nerve 1.4.2 Supra-orbital notch/foramen (incisura/foramen supraorbitalis) The transverse occipital suture lies in the upper part of the occipital – a notch or foramen above the orbit that is always present 1.7 squama and marks the boundary – contains the supra-orbital vessels and the 1.6 between the upper part of the oc- lateral branch of the supra-orbital nerve 1.1 cipital bone, which develops by 1.5 Zygomatic process (processus zygomaticus) 1 intramembranous ossification, and – connects to the zygomatic bone the lower part of the occipital bone, 1.6 Temporal line (linea temporalis) 1.2 which develops by endochondral ossification. – the upper border of the origin 3 of the temporalis muscle 1.5 Failure of fusion the transverse – continues on the parietal bone 2 occipital suture (sutura occipitalis 1.7 Parietal margin (margo parietalis) transversa) gives rise to the inter- – connects with the parietal bone parietal bones (Inca bones). These to form the coronal suture bones occur in 30 % of the Native Internal surface (facies interna) American population but only in 5 % 1.8 Groove for superior sagittal sinus Lateral view of the skull 1.1 of the European population. (sulcus sinus sagittalis superioris) The sutura mendosa is formed after – contains the superior sagittal sinus 1.7 1.2 incomplete fusion of the squamous 1.9 Frontal crest (crista frontalis) 1.4.2 1 part of the occipital bone. It projects – the site of attachment of the falx cerebri 1.5 medially or vertically from the lamb- 2 doid suture and is variable in length. – the anterior continuation of the groove 2.1 for the superior sagittal sinus 2.2 2 Orbital part (pars orbitalis) 1.4.1 The trochlear spine is a cartilagi- nous pulley in the trochlear fovea 2.1 Lacrimal fossa (fossa glandulae lacrimalis) 2.4 1.3 which is ossified in less than 15 % of – a fossa on the lateral part of the roof population. of the orbit for the lacrimal gland 2.2 Trochlear fovea (fovea trochlearis) The orbitocranial canal connects – fossa containing the trochlear spine Anterior view of the skull the orbit to the anterior cranial 2.3 Trochlear spine (spina trochlearis) 2.5 4 2 fossa. It opens into the anterior eth- – the attachment of the trochlea moidal foramen. of the superior oblique muscle 1 The orbitoethmoidal canal con- 2.4 Anterior and posterior ethmoidal foramina 2.6 nects the orbit to the ethmoidal air (foramen ethmoidale anterius et posterius) cells. It opens into the posterior eth- – formed by connection with the ethmoidal bone moidal foramen. – transmit the anterior and posterior ethmoidal artery, vein and nerve The internal occipital crest (crista 2.5 Ethmoidal notch (incisura ethmoidalis) occipitalis interna) is a vertical osse- ous crest. Sometimes it is replaced – a notch for the ethmoidal bone by the groove for the occipital sinus. 2.6 Sphenoidal margin (margo sphenoidalis) 3 Nasal part (pars nasalis) Internal surface of the cranial base The foramen caecum of the frontal – a small unpaired part of the bone located at the nasal root bone is a small hole on the cranial where the nasal spine and nasal margin are found surface of the squama of the fron- 1.7 4 Frontal sinus (sinus frontalis) – a paired paranasal sinus 1.8 tal bone. It represents a remnant of a foetal foramen and contains an – develops in children after the first year of life 1.9 emissary vein, which persists after – the full volume is reached at the end of the growth period 1 birth in about 1 % of the population. – opens into the middle nasal meatus 2.5 2 4.1 Septum of the frontal sinuses 2.6 (septum sinuum frontalium) Posterior view of the frontal bone – separates the left and right frontal sinus 4.2 Opening of the frontal sinus (apertura sinus frontalis) – the entrance to the frontal sinus 22 2.2 Occipital bone – Os occipitale 2 The occipital bone is an unpaired bone composed of four main parts: the squamous part, the basilar part and the two lateral parts. The basilar parts, the lateral parts and a portion of the squamous part contribute to the cranial base. These parts develop by endochondral ossification. A portion of the squamous part forms part of the cranial vault and develops by intramembranous ossification. 1 Foramen magnum – a large opening that contains the medulla oblongata as it changes into the spinal cord – contains the vertebral arteries, the anterior spinal artery, the paired posterior spinal arteries, the spinal root of the accessory nerve and the spinal vein 2 Basilar part (pars basilaris) – lies anterior to the foramen magnum and articulates with the sphenoid bone 2.1 Clivus – a slope on the internal surface located beneath the brain stem, basilar artery and basilar venous plexus 2.2 Pharyngeal tubercle (tuberculum pharyngeum) – an unpaired tubercle for the attachment of the pharyngeal raphe to the base of the skull 2.3 Groove for the inferior petrosal sinus (sulcus sinus petrosi inferioris) 4.7 2.4 Spheno-occipital synchondrosis (synchondrosis sphenooccipitalis) 4.1 – a cartilaginous connection between the sphenoid and occipital bone 4.5 4.2 3 Lateral parts (partes laterales) – located laterally to the foramen magnum 4.8 4.3 3.1 Occipital condyles (condyli occipitales) – protuberances for articulation with the atlas 4.6 4.4 3.2 Hypoglossal canal (canalis nervi hypoglossi) – transmits the hypoglossal nerve and venous plexus of the hypoglossal canal 3.3 Condylar fossa (fossa condylaris) – located behind the occipital condyle and may contain the condylar canal which transmits the condylar emissary vein Posterior view of the skull 3.4 Jugular notch (incisura jugularis) – forms the jugular foramen with the jugular notch of the temporal bone 3.4.1 Jugular process (processus jugularis) – a prominence at the end of the jugular notch for the origin of the rectus capitis anterior 2.2 3.4.2 Intrajugular process (processus intrajugularis) – is located inside 3.2 the jugular notch and separates the jugular foramen into two compartments 4 Squamous part (squama occipitalis) 2 3.4 External surface (facies externa) 3.1 4.1 Highest nuchal line (linea nuchalis suprema) – the attachment of the nuchal fascia 3 3.3 4.2 Superior nuchal line (linea nuchalis superior) 1 4 4.4 – the attachment of the trapezius and sternocleidomastoid 4.3 4.6 4.3 Inferior nuchal line (linea nuchalis inferior) 4.5 4.2 – the attachment of the rectus capitis posterior major and minor 4.1 4.4 Occipital plane (planum occipitale) – the attachment of some back muscles External surface of the cranial base 4.5 External occipital protuberance (protuberantia occipitalis externa) – a palpable tubercle on the posterior surface of the skull 4.6 External occipital crest (crista occipitalis externa) – a vertical crest for attachment of the nuchal ligament 4.7 Lambdoid border (margo lambdoideus) – forms the lambdoid suture with the parietal bone 2.1 4.15 4.8 Mastoid border (margo mastoideus) – connects to 2 2.3 the temporal bone to form the occipitomastoid suture 3.2 3.4 Internal surface (facies interna) 3 1 4.9 Cruciform eminence (eminentia cruciformis) – a cross-shaped prominence formed 4 4.13 by the grooves for the occipital, superior sagittal and transverse sinuses 4.14 – divides the occipital bone into two cerebral fossae and two cerebellar fossae 4.12 4.10 4.10 Internal occipital protuberance (protuberantia occipitalis interna) 4.11 – contains the confluence of sinuses, which is the connection point of the transverse, straight, superior sagittal and occipital sinuses Internal surface of the cranial base 4.11 Groove for superior sagittal sinus (sulcus sinus sagittalis superioris) 4.7 – contains the superior sagittal sinus and the attachment of the falx cerebri 4.12 Groove for transverse sinus (sulcus sinus transversi) 4.9 – contains the transverse sinus as well as the attachment of the tentorium cerebelli 4.16 4.13 Groove for sigmoid sinus (sulcus sinus sigmoidei) – contains the sigmoid sinus 4.14 Groove for occipital sinus (sulcus sinus occipitalis) 1 4.10 – contains the occipital sinus and the attachment of the falx cerebelli 4.15 Groove for marginal sinus (sulcus sinus marginalis) 3.2 – contains the marginal sinus and surrounds the foramen magnum 4.17 3.4 4.16 Cerebral fossae (fossae cerebrales) 2.1 4.8 – contains the posterior part of the occipital lobes of the telencephalon 2.4 4.17 Cerebellar fossae (fossae cerebellares) – contains the cerebellar hemispheres 3.1 – separated from the cerebral fossae by the tentorium cerebelli Oblique view of the occipital bone This copy belongs to Devosree De 23  2.3 Sphenoidal bone / sphenoid – Os sphenoidale Bones The majority of the sphenoidal bone The sphenoidal bone is an unpaired bone of the base of the skull that develops pre- develops by endochondral ossifica- dominantly by endochondral ossification. It consists of an unpaired body and three tion. However, the greater wings and the medial plate of the ptery- paired projections: the greater wing, lesser wing and pterygoid process. The spenoidal goid process develop by intramem- bone connects the middle cranial fossa to several topographical spaces of the skull via branous ossification. various foramina. These topographical spaces are the infratemporal fossa, pterygopala- tine fossa, tympanic cavity and the orbit. The sphenoidal bone is an pneumatised bone The middle clinoid process (processus clinoideus medius) is and contains a paired paranasal sinus: the sphenoidal sinus. a variable binate prominence situ- 2 ated medial to the carotid groove Basic parts 1 2 1 that serves for the insertion of the sellar diaphragm. 1 Body of the sphenoid 5 3 3 (corpus ossis sphenoidalis) The foramen of Arnold and cana- 2 Lesser wings 4 4 liculus innominatus are obsolete terms for the foramen petrosum. (alae minores ossis sphenoidalis) 3 Greater wings Left superior posterior view Left superior anterior view The foramen of Vesalius is an obso- (alae majores ossis sphenoidalis) of the sphenoid of the sphenoid lete term for the foramen venosum. 4 Pterygoid processes (processus pterygoidei) The pterygospinous process of 5 Superior orbital fissure 2 2 Civini (processus pterygospinosus) (fissura orbitalis superior) 5 is a variable feature located on the 1 5 posterior aspect of the lateral plate – an opening located between the greater 3 3 of the pterygoid process. It is a sharp and lesser wings bony protuberance that serves as 6 Inferior orbital fissure 6 the attachment of the pterygospi- (fissura orbitalis inferior) nous ligament. The pterygospinous – an opening between the greater wing ligament can ossify to create the fo- and the maxilla ramen of Hyrtl, containing the mo- Internal surface tor root of the mandibular nerve. Anterior view of the skull Body of sphenoid (corpus ossis sphenoidalis) of the cranial base The vomerovaginal canal (canalis 1 Sella turcica vomerovaginalis) is a small canal 1.1 Hypophysial fossa (fossa hypophysialis) without any content, formed be- tween the vaginal process of the – contains the hypophysis pterygoid process and the vomer. 1.2 Dorsum sellae – the posterior wall 4 1.3 Posterior clinoid processes 1.1 1.2 The cavernous sinus is discussed on (processus clinoidei posteriores) 1.3 page 534. – the attachment of the sellar diaphragm 2 and tentorium cerebelli 2 Carotid sulcus (sulcus caroticus) Left 3 superior posterior view of the sphenoid – a groove for the internal carotid artery – located lateral to the sella turcica 3 Sphenoidal lingula (lingula sphenoidalis) – the lateral margin of the carotid sulcus 4 Prechiasmaticus sulcus 4 1 – a shallow groove located anterior to the optic chiasma 5 Sphenoidal sinus (sinus sphenoidalis) Clinical notes – a paired paranasal sinus located inside Internal surface of the cranial base the sphenoid body and under the sella turcica The pterion is a craniometric point at the point where the greater wing 5.1 Septum of sphenoidal sinuses of the sphenoid bone, the parietal (septum sinuum sphenoidalium) bone and the frontal bone meet. – separates the left and right sphenoidal sinuses It is the weakest point of the skull. 5.2 Opening of sphenoidal sinus 7 The middle meningeal artery is lo- (apertura sinus sphenoidalis) cated underneath it on the internal – connects the sphenoidal sinus to surface of the skull. Trauma to this the superior nasal meatus region may result in bleeding of the middle meningeal artery, which re- 5.3 Sphenoidal concha (concha sphenoidalis) External surface of the cranial base sults in an epidural hematoma. – a rudimentary paired nasal concha that narrows 6 1.3 the opening of the sphenoidal sinus 1.2 From the developmental point of 6 Sphenoidal crest (crista sphenoidalis) 1.1 view, the pterion is the location of – a vertical crest in the midline of the ventral surface of 5 the fibrous sphenoidal fontanelle. the sphenoid body that articulates with the perpendicular plate of the ethmoidal bone 7 The pituitary gland can be accessed via the sphenoidal sinus. This is 7 Sphenoidal rostrum (rostrum sphenoidale) know as the transnasal transsphe- – a vertical crest on the inferior surface noidal approach and can be used to of the sphenoid body that articulates with the vomer Medial wall of the nasal cavity remove pituitary tumours. 24 2.3 Sphenoidal bone / sphenoid – Os sphenoidale 2 Lesser wing (ala minor ossis sphenoidalis) 1 2 2 2 1 1 Anterior clinoid process (processus clinoidei anteriores) – the attachment of the tentorium cerebelli 2 Optic canal (canalis opticus) – leads to the orbit – transmits the optic nerve and ophthalmic artery Left superior posterior view Cranial base Anterior view of the skull of the sphenoid Greater wing (ala major ossis sphenoidalis) 1 Infratemporal crest (crista infratemporalis) 5 9.1 – forms the border between the temporal and infratemporal fossae 5 3 4 4 – the origin of the superior head of the lateral pterygoid muscle 2 Spine of sphenoidal bone (spina ossis sphenoidalis) 3 – the most dorsal part of the sphenoid 9.2 – points downwards and is located near the foramen spinosum 1 9.3 – the attachment of the sphenomandibular ligament, 9.1 9.2 9.3 1 pterygospinous ligament and anterior ligament of the malleus 9.5 – the origin of the tensor veli palatini Left superior posterior view Left superior anterior view 3 Foramen rotundum – transmits the maxillary nerve (n. V2) of the sphenoid of the sphenoid 4 Foramen ovale – transmits the mandibular nerve (n. V3) 3 and the venous plexus of foramen ovale 4 5 Foramen spinosum – transmits the middle meningeal vessels 9.1 6 9.2 9.3 1 and the meningeal branch of the mandibular nerve 5 6 4 6 Petrosal foramen (foramen petrosum) 5 – a variable opening for the lesser petrosal nerve 7 Sphenoidal emissary foramen / foramen venosum – a variable opening for the sphenoidal emissary vein 8 Sulcus of the auditory tube (sulcus tubae auditivae) – contains the auditory tube (tuba auditivea), Internal view of the cranial base External view of the cranial basel which connects the tympanic cavity to the nasopharynx 9 Surfaces: 9.1 Cerebral surface (facies cerebralis) 9.2 Temporal surface (facies temporalis) 9.3 Infratemporal surface (facies infratemporalis) 9.2 9.5 9.2 9.4 Maxillary surface (facies maxillaris) 9.5 Orbital surface (facies orbitalis) 10 Margins: 10.1 Zygomatic margin (margo zygomaticus) 10.2 Frontal margin (margo frontalis) 10.3 Parietal margin (margo parietalis) Lateral view of the skull Anterior view of the skull 10.4 Squamosal margin (margo squamosus) Pterygoid process (processus pterygoideus) 2 2.1 1 Lateral plate (lamina lateralis) 1 4 – the origin of the inferior head of the lateral pterygoid muscle 2 Medial plate (lamina medialis) – the attachment of the 6 2 1 pharyngobasilar fascia and superior constrictor of the pharynx 5 4 2.1Pterygoid hamulus (hamulus pterygoideus) 2.1 – serves as a pulley for the tensor veli palatini tendon 3 Pterygoid notch (incisura pterygoidea) – a notch between the lateral and medial plates 4 Pterygoid fossa (fossa pterygoidea) – a fossa located between the lateral and medial plates 1 – the origin of the medial pterygoid muscle 2 Inferior aspect of the skull 5 Scaphoid fossa (fossa scaphoidea) –is located cranial to the pterygoid fossa – the origin of the tensor veli palatini 6 Pterygoid canal of Vidius (canalis pterygoideus) – transmits the vessels and nerve of the pterygoid canal 2 7 Vaginal process (processus vaginalis) 1 – a small prominence under the body of the sphenoid 1 2.1 – forms the palatovaginal canal, which transmits the pharyngeal nerve 2 4 and the pharyngeal branch of the maxillary artery Lateral wall of the nasal cavity Medial wall of the nasal cavity This copy belongs to Devosree De 25  2.4 Parietal bone – Os parietale Bones The granular foveolae (foveolae The parietal bone is a paired bone in the cranial vault that develops by intramembra- granulares) are small depressions nous ossification. It is square-shaped with an outward convexity formed by the parietal located adjacent to the groove for eminence (tuber parietale). the superior sagittal sinus. They are impressions formed by arachnoid 1 Surfaces granlulations. Internal surface (facies interna) Arachnoid granulations / arachnoid 1.1 Groove for the superior sagittal sinus 3.4 villi (granulationes arachnoideae) (sulcus sinus sagittalis superioris) 1.2 are pouches of arachnoid that proj- – contains the superior sagittal sinus ect into the dural venous sinuses to 1.2 Groove for the middle meningeal artery 1.3 allow cerebrospinal fluid to be ab- (sulcus arteriae meningeae mediae) sorbed into the blood. They are also 1.1 – contains the middle meningeal artery known as Pacchionian granulations. 1.3 Grooves for arteries (sulci arteriosi) 3.1 – grooves for the branches of the middle meningeal artery External surface (facies externa) Internal view of the cranial vault 1.4 Superior temporal line (linea temporalis superior) – the attachment of the temporal fascia 1.5 Inferior temporal line (linea temporalis inferior) – the inferior margin of the origin of the temporalis muscle 3.4 1.6 Parietal tuber (parietal eminence, tuber parietale) – contains an ossification center 3.3 – a thickened part of the bone with an outward convexity 1.7 Groove for the sigmoid sinus (sulcus sinus sigmoidei) 1.6 – a short groove for the sigmoid sinus located over the mastoid angle 3.1 2 Parietal foramen (foramen parietale) – transmits the parietal emissary vein External view of the cranial vault – located close to the sagittal border 3 Margins 3.3 3.1 Occipital border (margo occipitalis) 3.4 – connects to the occipital bone, forming 1.6 the lambdoid suture (sutura lambdoidea) 1.4 3.2 Squamous border (margo squamosus) 1.5 – connects to the temporal bone, forming the squamous suture (sutura squamosa) 3.2 3.1 3.3 Sagittal border (margo sagittalis) – connects to the contralateral parietal bone, External view of the left parietal bone forming the sagittal suture (sutura sagittalis) 3.4 Frontal border (margo frontalis) 4.1 3.3 – connects to the frontal bone, forming the coronal suture (sutura coronalis) 4 Angles 3.4 4.1 Frontal angle (angulus frontalis) 4.2 1.3 4.2 Occipital angle (angulus occipitalis) 1.2 4.3 Mastoid angle (angulus mastoideus) 4.4 4.4 Sphenoidal angle (angulus sphenoidalis) 3.1 3.2 4.3 Internal view of the right parietal bone 3.3 3.4 3.4 3.2 3.2 3.1 3.1 3.2 Clinical notes The triangle of Macewan is an ep- onym for the suprameatal triangle (foveola suprameatica). The supra- meatal triangle can be used to ap- Anterior view of the skull Posterior view of the skull Lateral view of the skull proach the mastoid antrum, which lies 1.5–2 cm deep to the surface of the bone. 26 2.5 Temporal bone – Os temporale 2 The temporal bone is a paired bone that consists of three main parts: the squamous part, the tympanic part and the petrous part. The squamous and tympanic parts of the temporal bone develop by intramembranous ossification. The petrous part and the styloid and mastoid process develop by endochondral ossification. The middle and inner ear are hidden inside the petrous bone. They open to the surroundings via the internal and external acoustic openings. The double-curved facial canal, housing the facial nerve, is located within the petrous part. The mastoid process is a pneuma- tised bony prominence containing small air filled cavities called mastoid air cells. Basic parts 1 Squamous part (pars squamosa) 2 Tympanic part (pars tympanica) 1 – forms the walls of the external acoustic meatus 2 – has the shape of the letter “U” 3 3 Petrous part (pars petrosa) Squamous part (pars squamosa) Basic parts of the temporal bone, 1 Parietal border (margo parietalis) – connects to the parietal bone, lateral view of the skull forming the squamous suture (sutura squamosa) 2 Sphenoidal margin (margo sphenoidalis) – connects to the sphenoidal bone, forming the sphenosquamous suture (sutura sphenosquamosa) 3 Groove for middle temporal artery (sulcus arteriae temporalis mediae) – a shallow vertical groove on the internal surface of the bone 1 4 Zygomatic process (processus zygomaticus) – the origin of the masseter 2 – the attachment of the lateral temporomandibular ligament and temporal fascia 4 – forms the zygomatic arch with the temporal process of the zygomatic bone 4.3 4.1 Articular surface (facies articularis) 5 4.2 Articular tubercle (tuberculum articulare) – a prominence in front of the mandibular fossa – forms part of the temporomandibular joint 4.3 Supramastoid crest (crista supramastoidea) Lateral view of the skull – part of the origin of the temporal muscle and temporal fascia – the dorsal continuation of the zygomatic process 4.4 Suprameatal triangle (foveola suprameatica) 1 – a small fossa located above the external acoustic meatus 4 4.5 Suprameatal spine (spina suprameatica) 4.2 4.3 – a variable osseous spine located under the suprameatal triangle 5 5 Mandibular fossa (fossa mandibularis) 2 – the articular fossa for the temporomandibular joint 8 Tympanic part (pars tympanica) External oblique view of the left temporal bone 6 External acoustic opening (porus acusticus externus) – the opening of the ear canal – is composed of a bony part and a cartilaginous part 7 Osseous external acoustic meatus (meatus acusticus externus osseus) – the bony part of the external acoustic meatus 7.1 Tympanic ring (anulus tympanicus) – a bony ring at the medial end of the external acoustic opening, covered by the tympanic membrane / eardrum 7.1.1 Tympanic sulcus (sulcus tympanicus) 7.1 7 6 – a groove in the tympanic ring for the attachment of the tympanic membrane 7.1.2 Tympanic notch (incisura tympanica) – a notch in the upper part of the tympanic ring – contains the pars flaccida of the tympanic membrane 8 Petrotympanic fissure (fissura petrotympanica) – a fissure located between the tympanic and petrous parts of the temporal bone – transmits the chorda tympani, anterior tympanic vessels and anterior ligament of the malleus 9 Tympanomastoid fissure (fissura tympanomastoidea) – the end of the mastoid canaliculus – transmits the auricular branch of the vagus nerve Frontal section of the principal parts of the ear 10 Tympanosquamous and petrosquamous fissure (fissura tympanosquamosa et petrosquamosa) This copy belongs to Devosree De 27  2.5 Temporal bone – Os temporale Bones Petrous part (pars petrosa) The pyramid (pyramis) is an obso- lete term for the petrous part of the 1 Apex of the petrous part (apex partis petrosae) 1 temporal bone. – points ventromedially 2 1.1 Internal opening of the carotid canal 2.1 3 The pyramidal crest is an obsolete term for the superior border of the (apertura interna canalis carotici) – transmits petrous part of the temporal bone. the internal carotid artery into the cranial cavity 4 – is located in the dorsal wall The ventrobasal surface is an ob- of the foramen lacerum 5.1 solete term for the portion of the 1.2 Musculotubal canal (canalis musculotubarius) petrous part of the temporal bone 4.1 1.2.1 Canal for auditory tube 2.4 which forms most of the walls of tympanic cavity. It can be accessed (semicanalis tubae auditivae) after removal of tympanic part of – the bony part of the auditory tube 2.5 the temporal bone. 1.2.2 Canal for tensor tympani muscle (semicanalis musculi tensoris tympani) 3.1 The facial nerve, see page 361. – contains the tensor tympani muscle 5 5.2 2 Anterior surface (facies anterior) The tympanic cavity, see page 506. 2.1 Trigeminal impression (impressio trigeminalis) Internal view of the cranial base The internal acoustic meatus, see – a shallow fossa for the trigeminal 2.5 2.4 2 2.2 2.3 page 507. ganglion (ganglion trigeminale) 1 – located near the apex of the petrous part 2.2 Groove for greater petrosal nerve 1.1 (sulcus nervi petrosi majoris) 1.2.2 – the continuation of the hiatus for the greater petrosal nerve 1.2.1 – transmits the greater petrosal nerve 2.3 Groove for lesser petrosal nerve (sulcus nervi petrosi minoris) – the continuation of the hiatus A cross section of the right temporal bone for the lesser petrosal nerve viewed from the right – transmits the lesser petrosal nerve from the tympanic cavity to the foramen ovale 2.4 Arcuate eminence (eminentia arcuata) 2.1 – a bulge formed by the anterior semicircular canal of the inner ear 2.5 Tegmen tympani – the roof of the tympanic cavity, 1 located anteromedial to the arcuate eminence – a weakened part of the skull 2 – is perforated by the veins of the tympanic cavity 4 3 Superior border (margo superior) 5 – the attachment of the tentorium cerebelli – contains the groove for the superior petrosal sinus 3.1 Groove for superior petrosal sinus Internal oblique view of the (sulcus sinus petrosi superioris) right temporal bone 4 Posterior surface (facies posterior) 4.1 Internal acoustic opening (porus acusticus internus) 2.4 2.5 – transmits the facial nerve, vestibulocochlear nerve 2.3 and labyrinthine vessels from the posterior cranial 2.2 fossa to the middle and internal ear 4.2 Subarcuate fossa (fossa subarcuata) – a small depression that may contain a small residual vein from development 4.3 External opening of vestibular canaliculus 5.1 (apertura externa canaliculi vestibuli) 4.1 – contains the endolymphatic sac 5.2 – the location of endolymph resorption 4.3.1 Vestibular canaliculus (canaliculus vestibuli) – contains the endolymphatic duct Internal oblique view of 5 Posterior border (margo posterior) – connects to the occipital bone the right temporal bone, 5.1 Groove for inferior petrosal sinus (sulcus sinus petrosi inferioris) 5.2 Jugular notch (incisura jugularis) – forms the jugular foramen (foramen jugulare) with the jugular notch of the occipital bone 5.3 Intrajugular process (processus intrajugularis) – a projection inside the jugular notch that divides the jugular foramen into two compartments 28 2.5 Temporal bone – Os temporale 2 Petrous part (pars petrosa) 6 Inferior surface (facies inferior) 6.1 Jugular fossa (fossa jugularis) – a fossa for the wide origin (superior bulb) of the internal jugular vein 6.1.1 Mastoid canaliculus (canaliculus mastoideus) – transmits the auricular branch of the vagus nerve 6.2 External opening of the carotid canal (apertura externa canalis carotici) 6.9 – the entrance of the carotid canal (canalis caroticus) 6.5 6.6 – transmits the internal carotid artery, the internal carotid plexus and the internal carotid venous plexus Lateral view of the skull 6.3 Petrosal fossula (fossula petrosa) – a little fossa between the jugular fossa and the external opening of the carotid canal – the entrance of the tympanic canaliculus – transmits the tympanic nerve and the inferior 6.2 tympanic vessels to the tympanic cavity 6.1 6.5 6.4 External opening of the cochlear canaliculus 6.11 (apertura externa canaliculi cochleae) – is located between 6 6.6 the jugular fossa and the external opening of the carotid canal 6.7 6.8 6.4.1 Cochlear canaliculus (canaliculus cochleae) 6.9 – contains the vein of the cochlear aqueduct 6.5 Styloid process (processus styloideus) Inferior surface of the cranial base – the origin of the stylohyoid, styloglossus and stylopharyngeus – the attachment of the stylohyoid and stylomandibular ligaments 6.6 Mastoid process (processus mastoideus) – a large pneumatised bony projection – the attachment of the sternocleidomastoid, splenius capitis and longissimus capitis 6.6.1 Mastoid cells (cellulae mastoideae) – air filled cavities that communicate anteriorly with the mastoid antrum 6.7 Mastoid notch (incisura mastoidea) 6.5 6.6 6.9 – the origin of the posterior belly of the digastricus External oblique view of the 6.8 Occipital groove (sulcus arteriae occipitalis) left temporal bone – a groove for the occipital artery, located medial to the mastoid notch 6.9 Mastoid foramen (foramen mastoideum) – transmits the mastoid emissary vein 6.10 Groove for sigmoid sinus (sulcus sinus sigmoidei) – is located on the internal surface of the mastoid process – contains the internal entrance of the mastoid foramen 6.11 Stylomastoid foramen (foramen stylomastoideum) – the external opening of the facial canal – transmits the facial nerve and the stylomastoid vessels 6.9 6.10 Facial canal of Falloppio (canalis nervi facialis) Internal oblique view of the The facial canal is a double-curved canal located inside the petrous part of the temporal bone. right temporal bone It contains the facial nerve. 1. The entrance is the area facialis of the fundus of the internal acoustic meatus. 1 2. The labyrinthine part (pars labyrinthica) runs ventrolaterally above the cochlea 2 at a right angle to the long axis of the petrous part of the temporal bone. 3 3. The geniculum houses the geniculate ganglion of the facial nerve. Here the canal makes a 90° turn laterocaudally. The greater petrosal nerve leaves in a small canal that also contains the petrosal branch of the middle meningeal artery. 4. The tympanic part (pars tympanica) runs dorsolaterally and parallel to the long axis of the petrosal part of the temporal bone between the medial and upper walls of the tympanic cavity. 5 4 6 5. The canal reaches the the posterior wall of the middle ear and makes a 90° turn downwards forming the prominence of the facial canal (prominentia canalis nervi facialis) in the mastoid antrum. 6. The mastoid part (pars mastoidea) runs caudally in the posterior wall of the 7 tympanic cavity. Two canals branch off here: the pyramidal eminence containing the nerve to the stapedius and the canaliculus of the chorda tympani which contains the chorda tympani and the posterior tympanic vessels. Section of the right temporal bone 7. The exit is the stylomastoid foramen, which trasmits both viewed from the right the facial nerve and the stylomastoid vessels. This copy belongs to Devosree De 29  2.6 Ethmoidal bone / ethmoid – Os ethmoidale Bones The cerebral falx (falx cerebri) The ethmoidal bone is an unpaired bone in the cranial base that develops by endo- is a fold of dura mater located chondral ossification. It consists of a horizontal plate, a vertical plate and the eth- between the two cerebral hemi- spheres. moidal labyrinth. The ethmoidal bone is a pneumatised bone containing a paranasal sinus: the ethmoidal air cells. The supreme nasal concha (concha nasalis suprema) is a variable con- 1 Perpendicular plate (lamina perpendicularis) – part of the nasal septum cha located on the roof of the nasal 2 Horizontal/cribriform plate (lamina cribrosa) cavity. 2.1 Cribriform foramina (foramina cribrosa) – transmit the olfactory nerves (fila olfactoria) Lamina papyracea ossis ethmoida- 2.2 Crista galli – a bony plate located in the middle of the ethmoid bone, lis is an obsolete term for the orbital protruding above the cribriform plate plate of the ethmoid bone. As the – part of the attachment of the falx cerebri name implies, this part of the eth- 3 Ethmoidal labyrinths (labyrinthi ethmoidales) moid bone is very thin and liable to 3.1 Orbital plate (lamina orbitalis) – the outer wall of ethmoidal cells, facing the orbit fracture. 3.2 Anterior and posterior ethmoidal foramina (foramen ethmoidale anterius et posterius) – are located between the ethmoidal and frontal bones The uncinate process of the middle nasal concha (processus uncinatus – transmit the anterior and posterior ethmoidal artery, vein and nerve conchae nasalis mediae) is con- 4 Ethmoidal cells (celullae ethmoidales) nected to the ethmoidal process 4.1 Anterior and middle ethmoidal cells (celullae ethmoidales anteriores et mediae) of the inferior nasal concha. These – open into the middle nasal meatus via the ethmoidal infundibulum two processes form the semilunar 4.1.1 Ethmoidal bulla (bulla ethmoidalis) – a bulge in the lateral wall of the middle hiatus, which lies within the maxil- nasal meatus formed by the anterior ethmoidal cells lary hiatus. 4.2 Posterior ethmoidal cells (celullae ethmoidales posteriores) – open into the superior nasal meatus 5 Nasal conchae (conchae nasales) – project medially into the nasal cavity – divide the nasal cavity into the nasal meati 5.1 Superior nasal concha (concha nasalis superior) 5.2 Middle nasal concha (concha nasalis media) 5.2.1 Uncinate process (processus uncinatus) – a dorsolateral arched projection of the middle nasal concha caudally to the inferior nasal concha 2.2 3 1 2.2 4 2.1 2 4 5.1 2.2 2 2.1 2 5.2 5.1 3.1 5.2 1 Posterior oblique view of Lateral wall of the nasal cavity Internal view of the cranial base the ethmoidal bone 2.7 Inferior nasal concha – Concha nasalis inferior Unlike the other conchae, the inferior nasal concha is an independent bone. The infe- rior nasal concha is connected to the maxilla and separates the inferior nasal meatus from the middle nasal meatus. 1 Inferior nasal concha (concha nasalis inferior) 1.1 Maxillary process (processus maxillaris) – connects to the lateral wall of the nasal cavity 1.2 Lacrimal process (processus lacrimalis) – connects to the lacrimal bone 1.3 Ethmoidal process (processus ethmoidalis) – connects to the uncinate process of the middle nasal concha 1.3 1.2 1.2 1.1 1 1 Left anterior view of the left inferior nasal concha Inferior nasal concha viewed from the left 30 2.8 Lacrimal bone, nasal bone and vomer – Os lacrimale, os nasale et vomer 2 The lacrimal bone is a small paired bone that develops by intramembranous ossification and forms part of the medial wall of the orbit. The nasal bone is also a small paired bone that develops by intramembranous ossification. It is attached to the nasal part of the frontal bone. The vomer is a small unpaired sagitally oriented bone that develops by intramem- branous ossification and forms the dorsal part of the nasal septum. 1 Lacrimal bone (os lacrimale) 1.1 Lacrimal groove (sulcus lacrimalis) – a rounded vertical groove 1.1.1 Fossa for the lacrimal sac (fossa sacci lacrimalis) – is formed by the lacrimal bone and maxilla 2 1 1.1 2 1.1.2 Posterior lacrimal crest (crista lacrimalis posterior) 1 – the dorsal border of the lacrimal fossa 3 – the attachment of the medial palpebral ligament and the origin of the deep part of the orbicularis oculi 1.2 Nasolacrimal canal (canalis nasolacrimalis) – a bony canal that leads to the nasal cavity Lateral view of the skull Anterior view of the skull – contains the nasolacrimal duct – is bordered by the lacrimal hamulus 2 Nasal bone (os nasale) 2.1 Ethmoidal groove (sulcus ethmoidalis) 2 3 – a groove for the nasal branch of the anterior ethmoidal nerve 2.2 2.2 Nasal foramen (foramen nasale) 2.1 Anterior oblique view – transmits the external nasal branch of External view of of the nasal bones the anterior ethmoidal nerve the cranial base 3 Vomer – forms the dorsal third of the nasal septum – divides at its cranial aspect into the paired alae of the vomer, 2 2 which are connected to the rostrum of the sphenoidal bone 2.1 – caudally connected to the nasal crest of the hard palate 1 3 – ventrocranially connected to the perpendicular plate of the ethmoidal bone Lateral view of the nasal cavity Middle wall of the nasal cavity 2.9 Zygomatic bone – Os zygomaticum The zygomatic bone is a paired bone of the viscerocranium that develops by intramembranous ossification. Together with the zygomatic process of the temporal bone it forms the zygomatic arch. It contains the zygomatic nerve, which bifurcates inside the bone into two terminal branches that innervate the skin overlying the zygomatic bone and the tem- poral fossa. 1 Orbital surface (facies orbitalis) – forms the lateral and caudal walls of the orbit 1.1 Zygomatico-orbital foramen (foramen zygomaticoorbitale) – the entrance for the zygomatic nerve 2 Temporal surface (facies temporalis) – forms the anterior wall of the temporal fossa 2.1 Zygomaticotemporal foramen (foramen zygomaticotemporale) – transmits the zygomaticotemporal nerve 1 3 Lateral surface (facies lateralis) 4 4 1.1 – forms the skeleton of the zygomatic region of the face 3.1 3.1 Zygomaticofacial foramen (foramen zygomaticofaciale) 3.1 3 5 3 – transmits the zygomaticofacial nerve 5 Projections 4 Frontal process (processus frontalis) 5 Temporal process (processus temporalis) – forms the zygomatic arch with the zygomatic Lateral view of the skull Anterior view of the skull process of the temporal bone 6 Orbital tubercle (tuberculum orbitale) – the attachment of the lateral palpebral ligament and the suspensory ligament of the eyeball This copy belongs to Devosree De 31  2.10 Palatine bone – Os palatinum Bones Involution of the alveolar process- The palatine bone is a paired bone of the viscerocranium that develops by intramem- es. After loss of the teeth, the alveo- branous ossification. It consists of two plates arranged perpendicularly to each other in lar processes (processus alveolaris) of both the maxilla and mandible an L-shape. These are the horizontal plate and the perpendicuar plate. The horizontal diminish in size. plate articulates with the maxilla, forming the hard palate. Palatine spines (spinae palatinae) 1 Horizontal plate (lamina horizontalis) are longitudinal ridges on the inferi- or (palatinal) surface of the maxilla. 1.1 Median palatine suture (sutura palatina mediana) – connects the two palatine bones in the midline Palatine grooves (sulci palatini) 1.2 Nasal crest (crista nasalis) – a bony ridge adjacent to are grooves between the palatine the median palatine suture and facing the nasal cavity spines for the branches of the great- 1.3 Palatine crest (crista palatina) – a bony ridge adjacent er palatine nerve and vessels (ner- to the median palatine suture and facing the oral cavity vus et vasa palatina majora). 1.4 Posterior nasal spine (spina nasalis posterior) The maxillary hiatus is narrowed by – the dorsal projection of the nasal crest the ethmoidal bulla, the uncinate – the origin of the musculus uvulae process of the middle nasal concha 1.5 Greater palatine foramen (foramen palatinum majus) and the palatine bone. – an opening on the lateral surface near 2 the connection with the maxilla 1.4 The incisive fossa (fossa incisiva) is – the terminal opening of the greater palatine canal, an anatomical term that is used for 1 which transmits the greater palatine nerve and vessels two different structures: 1.6 Lesser palatine foramina (foramina palatina minora) Anterior oblique view 1. A shallow pit above the first inci- sive tooth on the anterior surface of – are located dorsal to the greater palatine foramen of the palatine bones the maxilla. This is the origin of the – the terminal openings of the lesser palatine canals, which depressor septi nasi muscle (muscu- transmit the lesser palatine nerves and vessels lus depressor septi nasi) 1.7 Pyramidal process (processus pyramidalis) 2. A pit behind the incisive teeth on – connects to the lateral plate of the pterygoid process the incisive bone where the incisive – the origin of the medial pterygoid muscle foramina and the lower ends of the 2.2 1.8 Nasal surface (facies nasalis) – forms the dorsal part 2.3 incisive canals are situated. of the floor of the nasal cavity 2.7 1.9 Palatine surface (facies palatina) 2.1 – forms the dorsal part of the hard palate 1.5 2 Perpendicular plate (lamina perpendicularis) 1.2 1.7 2.6 2.1 Ethmoidal crest and conchal crest 1.8 (crista ethmoidalis et crista conchalis) – projections for the attachment of the middle and inferior nasal conchae Anterior oblique view of the palatine bones 2.2 Orbital and sphenoidal process (processus orbitalis et sphenoidalis) 1.1 – two cranial processes 1.9 – form the sphenopalatine notch 2.3 Sphenopalatine foramen 1.5 (foramen sphenopalatinum) – an opening 1.6 formed by the sphenoid bone and the sphenopalatine notch of the palatine bone 2.7 – transmits the sphenopalatine artery and posterior superior lateral and medial nasal branches of the maxillary nerve External view of the cranial base 2.4 Grater palatine canal (canalis palatinus major) – is located between the maxillary bone and a groove on the maxillary surface of the palatine bone – transmits the greater palatine nerve and vessels 2.5 Lesser palatine canals (canales palatini minores) – branches of the greater palatine canal – transmit the lesser palatine nerves and vessels 2.6 Maxillary surface (facies maxillaris) – points towards the maxilla 2 2 2.7 Nasal surface (facies nasalis) 1 1 – forms the dorsal part of the lateral wall of the nasal cavity Oblique section through Middle wall of the nasal cavity the nasal cavity 32 2.11 Maxilla – Maxilla 2 The maxilla is a paired bone of the viscerocranium that develops by intramembranous ossification. It consists of a body with four surfaces and four processes. The maxilla is a pneumatised bone and contains the largest paranasal sinus: the maxillary sinus. 1 Body of maxilla (corpus maxillae)