GUIDE

Head and Neck: Bones and Ligaments

Bones of head and neck

Skull

Mandible

Cervical vertebrae

Skull

The skull is divided into the neurocranium or calvaria (contains the brain and its meningeal coverings) and the viscerocranium (facial skeleton). The skull is composed of 22 bones (excluding the middle ear ossicles), with 8 forming the cranium and 14 forming the face. The orbits (eye sockets) lie between the calvaria (skull cap) and the facial skeleton and are formed bycontributions from 7 different bones.

[Plate 5 - Skull: Anteroposterior Radiograph]

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Function of skull

Encloses, supports and protects brain and meninges

Contains foramina for the transmission of nerves and vessels

Forms foundation for the face

Contains specialized cavities and openings for sense organs (e.g., nasal, oral)

Neurocranium

Cranial vault and base of skull

Encloses and protects brain

Composed of 8 bones

Bones united byinterlocking sutures

Can be divided

Calvaria-dome-like roof

Cranial base

Calvaria composed of 4 bones

Frontal bone anteriorly

Occipital bone posteriorly

Two parietal bones laterally

Cranial base formed from

Ethmoid bone

Parts of occipital and temporal bones

Viscerocranium

= facial skeleton

Composed of 14 bones

Encloses orbits, nose, paranasal sinuses, mouth, and pharynx

Maxillae and mandible form upper and lower jaw, respectively, and house the teeth

There are also three auditoryossicles

Malleus, incus, and stapes

Found spanning tympanic cavity

First bones to be completelyossified during development

Major sutures of the skull

Most bones of the skull are bound bysutures, a type of fibrous joint that fuses with age and becomes immobile.

Coronal suture separates frontal and parietal bones

Sagittal suture separates two parietal bones

Lambdoid suture separates parietal and temporal bones from occipital bones

Squamous suture separates squamous part of temporal bone from parietal bone

Sphenosquamous suture separates squamous part of temporal bone from greater wing of the sphenoid

Metopic suture between two frontal bones is largelyobliterated with fusion of frontal bones

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[Plate 6, Skull: Lateral View]

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[Plate 7, Skull: Lateral Radiograph]

Internal Features of Base of Skull

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Divided into anterior, middle, and posterior cranial fossae Anterior cranial fossa

Contains frontal lobe of brain

Formed byfrontal bone anteriorly, ethmoid bone medially, and lesser wing of sphenoid posteriorly

Features

Frontal crest-midline bonyextension of frontal bone

Foramen cecum-foramen at base of frontal crest

Crista galli-Midline ridge of bone from ethmoid posterior to foramen cecum

Cribriform plate-Thin, sieve-like plate of bone on either side of crista galli, which transmits olfactorynerves from nasal cavity to olfactorybulbs

Middle cranial fossa

Contains temporal lobe, hypothalamus, and pituitarygland

Formed bygreater wing and bodyof sphenoid, petrous temporal bone, lesser wing sphenoid

Features

Sella turcica-central depression in bodyof sphenoid for pituitarygland

Tuberculum sellae-Swelling anterior to sella turcica

Dorsum sellae-crest on bodyof sphenoid posterior to sella turcica

Anterior clinoid processes-medial projections of lesser wings of sphenoid bones

Posterior clinoid processes-swelling at either end of dorsum sellae

Foramen lacerum (one on each side)-jagged opening closed byplate of cartilage in life, transmits nothing

Contains four foramina in a crescent on either side in the bodyof the sphenoid

Superior orbital fissure

Foramen rotundum

Foramen ovale

Foramen spinosum Posterior cranial fossa:

Contains cerebellum, pons, and medulla oblongata

Composed largelyof occipital bone, bodyof sphenoid, petrous, and mastoid parts of temporal bone

Features

Foramen magnum-transmits spinal cord

Internal occipital crest-divides posterior fossa into two lateral cerebellar fossae

Grooves for transverse and sigmoid dural venous sinuses

Jugular foramen-transmits sigmoid sinus (internal jugular vein) and several cranial nerves

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Internal acoustic meatus-anterior and superior to jugular foramen, transmits facial and vestibulocochlear nerves (CN VII and CN VIII)

Hypoglossal canal-anterolateral and superior to foramen magnum, transmits hypoglossal nerve (CN XII)

Foramina of Skull

Numerous holes appear in the cranial floor and theyare called foramina. Important structures, especiallycranial nerves arising from the brain, pass through the foramen to access the exterior.

[Plate 10, Cranial Base: Inferior View]

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[Plate 11, Cranial Base: Superior View]

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Posterior meningeal artery

Mandible

[Plate 17, Mandible]

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Unpaired bone of lower jaw Largest and strongest bone in face

Articulates with temporal bone at temporomandibular joint Consists of

Body

Can be divided into lower base and upper alveolar part

Has a mental protuberance anteriorlyand inferiorlywhere two sides come together

Mental spine: rough projection on inner surface of bodyin the midline

Mental foramen below second premolar transmits terminal branch of inferior alveolar nerve to supplyskin and mucus membrane of lower lip and chin

Mylohyoid line: a ridge extending upward and backward on internal surface of alveolar part of mandible for attachment mylohyoid muscle

Submandibular fossa: long depression below mylohyoid line, which accommodates submandibular gland

Sublingual fossa: concavities on either side of mental spine for sublingual gland

Rami

Lateral vertical projections from body

Each meets bodyinferiorlyat angle of the jaw

Two processes at superior end: coronoid process and condylar process

Coronoid process-attachment of temporalis muscle

Condylar process-part of temporomandibular joint

Mandibular notch-concavitybetween condylar and coronoid processes

Mandibular foramen

On inner surface of ramus

Entrance to mandibular canal, through which passes the inferior alveolar nerve

Lingula-thin projection of bone overlapping mandibular foramen

Mylohyoid groove-groove leading anteriorlyand inferiorlyfrom mandibular foramen indicating course of mylohyoid nerve and vessels

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Temporomandibular Joint

[Plate 18, Temporomandibular Joint]

The mandible articulates with the temporal bone and in chewing or speaking, it is onlythe mandible or lower jaw that moves; the upper jaw or maxilla remains stationary. The teeth are contained in the alveolar portion of the mandible.

Articulation between condylar process of mandible, articular tubercle of temporal bone, and mandibular fossa

Modified hinge-type synovial joint

Contains fibrocartilaginous disc, which divides joint cavityinto two compartments

Gliding movements (protrusion and retrusion/retraction) occur in upper compartment

Hinge movements (depression and elevation) occur in lower compartment

Stabilized bythree ligaments:

Lateral temporomandibular ligament

Lateral thickened parts of articular capsule

Prevent posterior dislocation of joint

Sphenomandibular ligament

Primarypassive support

Runs from spine of sphenoid to lingual of mandible

Serves as swinging hinge and check ligament

Stylomandibular ligament

Thickening in capsule of parotid gland

Runs from styloid process to angle of mandible

Movements

Depression-suprahyoid and infrahyoid muscles, gravity

Elevation-temporalis, masseter, and medial pterygoid muscles

Protrusion-lateral pterygoid, masseter, medial pterygoid

Retraction/retraction-temporalis, masseter

Side to side grinding-retractors of same side, protruders of opposite side

Cervical vertebrae

See: Back and Spinal Cord-Bones and Ligaments

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