Anatomy of the Skull PDF

Anatomy of the skull By Dr. Shilan Hussein Assistant Professor of Anatomy Objectives: ► By the end of the theory and the practical lectures the students should be able to; ► *Identify the bones, views and the sutures of the skull. ► * Identify the foramina of the skull and the structures pas...

Anatomy of the skull By Dr. Shilan Hussein Assistant Professor of Anatomy Objectives: ► By the end of the theory and the practical lectures the students should be able to; ► *Identify the bones, views and the sutures of the skull. ► * Identify the foramina of the skull and the structures passing through each. ► *parts of the mandible with its muscle attachments.(Muscles of mastication) ► Parts of the cranial cavity and contents. ► The Head ► The head is formed mainly by the skull with the brain and its covering meninges enclosed in the cranial cavity. ► The special senses, the eye and the ear, lie within the skull bones or in the cavities bounded by them. ► The term skull includes the mandible, ► The cranium is the skull without the mandible. ► The cranial cavity has a ► roof or cranial vault, and a floor which is the base of the skull. a ► The facial skeleton is the front part of the skull and includes the mandible. Bones of the Skull Composition ► The skull is composed of several separate bones united at immobile joints called sutures. ► The connective tissue between the bones is called a sutural ligament. ► The mandible is an exception to this rule, for it is united to the skull by the mobile temporomandibular joint ► The bones of the skull can be divided cranium and face. ► ► The vault is the upper part of the cranium, the base of the skull is the lowest part of the cranium cranium ► The cranium consists of the following bones, two of ► which are paired : ► ■■ Frontal bone: 1 ► ■■ Parietal bones: 2 ► ■■ Occipital bone: 1 ► ■■ Temporal bones: 2 ► ■■ Sphenoid bone: 1 ► ■■ Ethmoid bone: 1 The facial bones ► The facial bones consist of the following, two of which are ► single: ► ■■ Zygomatic bones: 2 ► ■■ Maxillae: 2 ► ■■ Nasal bones: 2 ► ■■ Lacrimal bones: 2 ► ■■ Vomer: 1 ► ■■ Palatine bones: 2 ► ■■ Inferior conchae: 2 ► ■■ Mandible: 1 External features ► Superior view ► Anteriorly the frontal bone articulates with the pair of parietal bones at the coronal suture, which runs transversely. ► The midline meeting place of the frontal and parietal bones is the bregma, the site of the anterior fontanelle itwilloccifiedatismonths Posterior view ► The lambda is the midline point where the sagittal suture meets the tortuous lambdoid suture between the squamous part of the occipital and the parietal bones. ► Behind the bregma the parietal bones articulate in the midline sagittal suture. ► The sagittal suture curves down to the lambda, at the apex of the occipital bone. ► Some 6 cm below the lambda the occipital bone is projected into the external occipital protuberance, from which a ridge curves, convex upwards, towards the base of the mastoid process Lateral view ► The coronal suture comes down along the ► side of the skull to reach the curved upper border of the greater wing of the as sphenoid, which thus articulates posteriorly with the parietal bone and anteriorly with the frontal bone. ► The resulting H-shaped pattern of sutures in this ► region between frontal, parietal, temporal and sphenoid bones is called the pterion gomati archis formed by zygomaticprocess in of auditors petrouspart insidethe skull Anterior view Inferior view ► The area behind the foramen magnum consists of the squamous part of the occipital bone. ► The superior nuchal line lies in a curve concentric with the foramen magnum. sopalatinenerve greaterpalatine nerve form zygomatic arch 19 rata wa mandibular nerve c g'imantery foramen s pinosa transmit.in iiiiiii fossa lesserwing cranial fossa posterior cranial fossa c prayer forga t.sinum cg Musclesof mastication is supplybytrigeminalnerve orcyndgle mark 0 iiifule i vessel The Mandible ► ► ► The mandible or lower jaw is the largest and strongest bone of the face, and it articulates with the skull at the temporomandibular joint. The mandible consists of a horseshoe-shaped body and a pair of rami. The body of the mandible meets the ramus on each side at the angle of the mandible. ► The body of the mandible, on its external surface in the midline, has a faint ridge indicating the line of fusion of the two halves during development at the symphysis menti. ► The mental foramen can be seen below the second premolar tooth; it transmits the terminal branches of the inferior alveolar nerve and vessels. ► . The mylohyoid line can be seen as an oblique ridge that runs backward and laterally from the area of the mental spines to an area below and behind the third molar tooth. ► The submandibular fossa, for the superficial part of the submandibular salivary gland, lies below the posterior part of the mylohyoid line. ► The sublingual fossa, for the sublingual gland, lies above the anterior part of the mylohyoid line. ► The upper border of the body of the mandible is called the alveolar part; in the adult, it contains sockets for the roots of the teeth. ► The lower border of the body of the mandible is called the base. ► The ramus of the mandible is vertically placed and has an anterior coronoid process and a posterior condyloid process, or head; the two processes are separated by the mandibular notch. ► On the lateral surface of the ramus are markings for the attachment of the masseter muscle. ► On the medial surface is the mandibular foramen for the inferior alveolar nerve and vessels. ► In front of the foramen is a projection of bone, called the lingula, for the attachment of the sphenomandibular ligament. ► The foramen leads into the mandibular canal, which opens on the lateral surface of the body of the mandible at the mental foramen. ► The coronoid process receives on its medial surface the attachment of the temporalis muscle. Below the condyloid process, or head, is a short neck. Vault of the Skull ► The internal surface of the vault shows the coronal, sagittal, and lambdoid sutures. ► In the midline is a shallow sagittal groove that lodges the superior sagittal I sinus. ► On each side of the groove are several small pits, called granular pits, which lodge the lateral lacunae and arachnoid granulate.ons ooooh ► .Several narrow grooves are present for the anterior and posterior divisions of the middle meningeal vessels as they pass up the side of the skull to the vault. Base of the Skull ► The interior of the base of the skull is divided into three cranial fossae: anterior, middle, and posterior. ► The anterior cranial fossa is separated from the middle cranial fossa by the lesser wing of the sphenoid, and the middle cranial fossa is separated from the posterior cranial fossa by the petrous part of the temporal bone. Anterior fossa cranial middle cranial fossa posterior cranial fossa Anterior Cranial Fossa ► The anterior cranial fossa lodges the frontal lobes of the cerebral hemispheres. ► It is bounded anteriorly by the inner surface of the frontal bone, and in the midline is a crest for the attachment of the falx cerebri. Its posterior boundary is the sharp lesser wing of the sphenoid, ► The floor of the fossa is formed by the ridged orbital plates of the frontal bone laterally and by the cribriform plate of the ethmoid medially . ► The crista galli is a sharp upward projection of the ethmoid bone in the midline for the attachment of the falx cerebri. Middle Cranial Fossa ► The middle cranial fossa consists of a small median part and expanded lateral parts . ► The median raised part is formed by the body of the sphenoid, and the expanded lateral parts form concavities on either side, which lodge the temporal lobes of the cerebral hemispheres ► The sphenoid bone resembles a bat having a centrally placed body with greater and lesser wings that are outstretched on each side. canal optic anteriorclinoidprocess clinoid posterior process rotence foramen dorsumsetae a of ► Anteriorly, the optic canal transmits the optic nerve and the ophthalmic artery, a branch of the internal carotid artery. ► The superior orbital fissure, which is a slitlike opening between the lesser and the greater wings of the sphenoid, transmits ► the lacrimal, frontal, trochlear, oculomotor, sonasociliary, and abducent ago nerves, together with the superior ophthalmic vein. ► The foramen rotundum, which is situated behind the medial end of the superior orbital fissure, transmits the maxillary nerve from the trigeminal nerve. ► The foramen ovale ► transmits the mandibular nerve . or ► The foramen spinosum lies posterolateral to the foramen ovale and. The foramen transmits the middle meningeal artery. ► The large and irregularly shaped foramen lacerum . ► The carotid canal opens into the side of the foramen lacerum above that transmits The internal carotid artery. ► The median part of the middle cranial fossa is formed by the body of the sphenoid bone. a Is ► In front is the sulcus chiasmatis, which is related to the optic chiasma and leads laterally to the optic canal on each side. ► Behind the elevation is a deep depression, the sella turcica, which lodges the pituitary gland. I The sella turcica is bounded posteriorly by a square plate of bone called the dorsum sellae. ► ► IS The superior angles of the dorsum sellae have two tubercles, called the posterior clinoid processes. Posterior Cranial Fossa ► Anteriorly, the fossa is bounded by the superior border of the petrous part of the temporal bone, and posteriorly it is bounded by the occipital bone. ► The foramen magnum occupies the central area of the floor and transmits the medulla oblongata and its surrounding meninges, the ascending spinal parts of the accessory nerves, and the two vertebral arteries. ► The hypoglossal canal is situated above the anterolateral boundary of the foramen magnum and transmits the hypoglossal nerve (12th cranial nerve). ► The jugular foramen ► Transmits the 9th (glossopharyngeal nerve), 10th (vagus nerve), and 11th as (Accessory nerve )cranial nerves and the internal jugular vein. ► ► The internal acoustic meatus It transmits the vestibulocochlear nerve(8th vranial nerve) and of the facial nerve (7th cranial nerve). me e The internal occipital crest Characteristics of a Typical Cervical Vertebra ► A typical cervical vertebra has the following characteristics : ► ■ The transverse processes possess a foramen transversarium for the passage of the vertebral artery and veins (note that the vertebral artery passes through the transverse processes C1 to 6 and not through C7). ► ■ The spines are small and bifid. f ► ■ The body is small and broad from side to side. ► ■ The vertebral foramen is large and triangular. Characteristics of the Atypical Cervical Vertebrae ► The 1st, 2nd, and 7th cervical vertebrae are atypical. ► The 1st cervical vertebra, or atlas , ► does not possess a body or a spinous process. ► It has an anterior and posterior arch. ► I It has a lateral mass on each side with articular surfaces on its upper surface for articulation with the occipital condyles (atlanto-occipital joints) and articular surfaces on its inferior surface for articulation with the axis (atlantoaxial joints). Atlas The 2nd cervical vertebra, or axis ► Has a peglike odontoid process (dens) that projects from the superior surface of the body (representing the body of the atlas that has fused with the body of the axis). Axis The 7th cervical vertebra (C7) F ► , or vertebra prominens , is so named because it has the longest spinous process, ► the process is not bifid. ► The transverse process is large, ► but the foramen transversarium is small and transmits the vertebral vein or veins. The 7th cervical vertebra (C7)