Skull and cranial nerves

Abducent nerve (CNVI)

(F) Motor: lateral rectus muscle of eye

What bone is the last to fuse in a human skull?

Mandible; fuses early in the 2nd year

Sella turcica

(L. Turkish saddle) is the saddle-like bony formation on the upper surface of the body of the sphenoid. The hypophyseal fossa, the "bed" of the pituitary gland, like the posts of a four-poster bed.

Endochondral ossification

(hyaline) cartilage models of bones form from mesenchyme during the fetal period, and bone subsequently replaces most of the cartilage. These bones include bones of the skull.

Clinical significance of a fractured pterion

A hard blow to the side of the head may fracture the thin bones forming the pterion, producing a rupture of the frontal branch of the middle meningeal vessels, which lie in grooves on the internal aspect of the lateral wall of the skull. The resulting hematoma exerts pressure on the underlying cerebral cortex. An untreated middle meningeal vessel hemorrhage may cause death in a few hours.

Fontanelles

Areas in the infant's skull that have not fused together allowing the skull movement as it exits the birth canal. The anterior is not clinically palpable by 18 months, and the posterior not palpable by the end of 1st year (before then can feel a soft spot)

Temporal bone

Bone forming the opening of the external acoustic meatus, mastoid process and styloid process.

Identify #5

Clivus of the occipital bone; front part of the occipital bone that articulates with the sphenoid

Each cranial nerve can have many function because ___________________________________________

Each cranial nerve can contain many functional groups of fibres: somatic sensory/motor, visceral sensory/motor, branchiomotor (develop from face) and special sensory (e.g. smell and vision) Each functional group of fibres is associated with a specific cranial nerve nucleus in the brainstem

Occipital bone

Forms the most posterior part of the skull and the base of the cranium.

Pterion

H-shaped formation of sutures that unite the frontal, parietal, sphenoid (greater wing), and temporal bones.

Face to cranium ratio in infants

In infants, ratio of face to cranium is large. Many of the bones haven't yet fused

Hydrocephalus

Increased amount of cerebrospinal fluid in the ventricles of the brain, can cause enlargement of the cranium in infants. The skull bones have not yet fused and thus the cranial bones are separated outwards

Foramina in the posterior cranial fossa

Internal acoustic meatus: opens into the inner ear; facial (CNVII) and vestibulocochlear nerves (CN VIII), and the labyrinthine artery Hypoglossal canal: hypoglossal nerve (CN XII) Foramen magnum: medulla, vertebral arteries, spinal root of Accessory N (CNXI), Spinal arteries

Foramen lacerum

It is closed by a cartilage plate. Only some meningeal arterial branches and small veins are transmitted vertically through the cartilage, completely traversing this foramen. The internal carotid artery and its accompanying sympathetic and venous plexuses pass across the superior aspect of the cartilage (does not actually go through it)

Occulomotor nerve (CNIII)

Motor: all extrinsic muscles of eye except those listed for CNIV and VI

Hypoglossal nerve (CNXII)

Motor: all intrinsic and extrinsic muscles of tongue (excluding palatoglossus— a palatine muscle)

Facial nerve (CNVII)- primary root

Motor: muscles of facial expression + 3 other muscles

Trigeminal nerve (CNV)- motor root

Motor: muscles of mastication and 4 other muscles

Vagus nerve (CNX)

Motor: palate, pharynx, larynx, trachea, bronchial tree, heart, GI tract to left colic flexure Sensory: pharynx, larynx; reflex sensory from trachiobronchial tree, lungs, heart, GI tract to left colic flexure

Spinal accessory nerve (CNXI)

Motor: sternocleidomastoid and trapezius

Glossopharyngeal nerve (CNIX)

Motor: stylopharyngess, parotid gland Sensory: taste from posterior third of tongue; general sensation: pharynx, tonsillar sinus, pharyngotympanic tube, middle ear cavity

Facial nerve (CNVII)- intermediate root

Motor: submandibular, sublingual, lacrimal, nasal and palatine glands Sensory: taste from anterior 2/3 of tongue, soft palate

Trochlear nerve (CNIV)

Motor: superior oblique muscle of eye

Foramina in the middle cranial fossa

Optic canal Superior orbital fissure: nerves for eye movement and ophthalmic veins Foramen rotunda: V2 Foramen vale: V3 Foramen spinosum: middle meningeal artery and vein

Which cranial bones lie between the occipital and frontal bone, making up most of the lateral side of the skull?

Parietal bones

Zygomatic process

Process of the temporal bone that attaches to the zygoma to form the zygomatic arch.

Trigeminal nerve (CNV)- sensory root

Sensory: face; oral, nasal, and sinus mucosa; teeth; anterior two thirds of tongue

Olfactory nerve (CNI)

Special sensory: smell

Optic nerve (CNII)

Special sensory: vision

Middle cranial fossa

The butterfl y-shaped middle cranial fossa has a central part composed of the sella turcica on the body of the sphenoid and large, depressed lateral parts on each side.

Name the 3 cranial sutures found on the superior aspect of the skull.

The coronal suture separates the frontal and parietal bones, the sagittal suture separates the parietal bones, and the lambdoid suture separates the parietal and temporal bones from the occipital bone.

Anterior cranial fossa

The inferior and anterior parts of the frontal lobes of the brain occupy the anterior cranial fossa, the shallowest of the three cranial fossae. The fossa is formed by the frontal bone anteriorly, the ethmoid bone in the middle, and the body and lesser wings of the sphenoid posteriorly

Mandible

U-shaped bone with an dental arch that supports the mandibular teeth. It consists of a horizontal part, the body, and a vertical part, the rami (which attach to the temporal bone)

Vestibulocochlear nerve (CNVIII)

Vestibular nerve, sensory: equilibrium, motion Cochlear nerve, sensory: hearing

Sphenoid bone

Wedged between the frontal, temporal, and occipital bones is the sphenoid, an irregular unpaired bone that consists of a body and three pairs of processes: greater wings (orange), lesser wings (blue) and pterygoid processes.

Intramembranous ossification

bones that develop from a fibrous tissue precursor. These bones include the flat bones of the skull as well as parts of the clavicle and mandible.

Frontal bone

flat part, forms the skeleton of the forehead, articulating inferiorly with the nasal and zygomatic bones. It also contributes to the nasal cavity and the orbit

Maxilla

form the upper jaw and cheeks; have a dental arch with tooth sockets (alveoli) and constitute the supporting bone for the maxillary teeth. They have broad connection with the zygomatic bones laterally and an infra-orbital foramen inferior to each orbit for passage of the infra-orbital nerve and vessels

What articulates at the mandibular fossa?

mandibular fossa is the depression in the temporal bone that articulates with the mandible (tempo-mandibular joint).

Zygomatic bone

palpable back end of the cheek bones; form the prominences of the cheeks, lie on the inferolateral sides of the orbits and rest on the maxillae.

Tempomandibular bone

provides mandible movement when opening the mouth e.g. chewing

Posterior cranial fossa

the largest and deepest of the three cranial fossae, lodges the cerebellum, pons, and medulla oblongata. Formed by parts of the sphenoid, temporal, parietal, and occipital bones.

Crista gali

thick, median ridge of bone which projects superiorly from the ethmoid. On each side of this ridge is the sieve-like cribriform plate of ethmoid bone. Its numerous tiny foramina transmit the olfactory nerves (CN I) from the olfactory areas of the nasal cavities to the olfactory bulbs of the brain, which lie on this plate.

Jugular foramen

transmits several cranial nerves (vagus and glossopharyngeal nerves) in addition to the sigmoid sinus that exits the cranium as the internal jugular vein (venous drainage from the brain occurs via the dural venous sinuses and internal jugular veins).