Lecture #26 - Skull, Scalp, and Face

Splanchnocranium

"splanchno" means related to viscus or alimentary canal. This is the facial region that houses the receptor organs for special senses including smell, taste, and vision

Divisions of the Skull

A line drawn from the supraorbital ridge to the mastoid process separates the skull into two major parts; neurocranium and splanchocranium

Facial v.

Accompanies the facial a. but ends by emptying int the internal jugular v. deep to sternocleidomastoid

Facial a.

Branch of external carotid a. that appears at the inferior border of the body of the mandible and ascends the face deep to zygomaticus major toward the medial angle of the eye, where its continuation is called the angular a.

Transverse Facial a.

Branch of the superficial temporal a. that crosses the face superficial to the masseter m. to anastomose with the branches of the facial a.

Sensory Innervation Posterior to the Ears

Branches from spinal nerves C2 and C3 and the lesser occipital n.

Sensory Innervation Anterior to the Ears

Branches of the trigeminal nerve

Unpaired Bones of the Skull

Ethmoid Sphenoid Mandible Vomer Occipital Frontal - initially two bones separated by the metopic suture, which fuses after birth

Fontanelles

Expanded areas of fibrous tissue that covers the spaces between the cranial bones in fetuses and infants. These allow significant changing and molding of the cranium during childbirth.

Borders of the Scalp

Extends from superior nuchal line to supraorbital margins, and laterally between the zygomatic arches

Sensation to the Face

Most is innervated by the trigeminal nerve, with small contributions from the facial n. to the skin around the auricle, and the great auricular n., which supplies some of the skin at the angle of the mandible and near the auricle

Orbicularis Oculi m.

Muscle of facial expression with a thin palpebral part that lightly closes the eyelids, or blinks, to keep the cornea moist. Also has a thick orbital part that closes the eyelids tightly during squinting

Buccinator m.

Muscle of the cheek. Important in feeding as it is responsible for holding food items between the upper and lower teeth

Levator Palpebrae m.

Muscle of the eyelid that is not involved in facial expression because it is innervated by occulomotor n. It is responsible for lifting the upper eyelid

Muscles of the Nose

Nasalis and procerus mm. act on the nose

Facial n. - CN VII

Supplies all the muscles of facial expression. Has 6 branches, Posterior Auricular n. in addition to 5 which branch within the parotid gland. They are; Temporal Zygomatic Buccal Mandibular Cervical (Ten Zebras Bit My Chicken...?)

Ophthalmic n. V1

Supplies the forehead. One of its branches, the frontal n., divides within the orbit to become supratrochlear and supraorbital nn.

Maxillary n. V2

Supplies the infraorbital region, including the upper toothrow. Its largest branch is the infraorbital n., but also branches into zygomaticofacial n. and zygomaticotemporal n.

Mandibular n. V3

Supplies the mandibular region, including the lower toothrow. It is also motor to the muscles of mastication

Venous Drainage of the Scalp

Supraorbital and supratrochlear vv. unite at the medial angle of the eye to form the angular vv. which communicates with the ophthalmic vv. which may allow facial infections to reach the cavernous sinus. The angular v. then becomes the facial v.

Branches of the Internal Carotid a. that Supply the Scalp

Supratrochlear a. Supraorbital a. which can be monitored by Doppler ultrasound devices to indirectly assess the quantity of blood flow in the internal carotid a.

Branches of the External Carotid a. that Supply the Scalp

Occipital a. Posterior auricular a. Superficial temporal a.

Characteristic of Facial Muscles

The muscles of facial expression are either sphincters or in association with sphincters

Superficial Temporal a.

The smaller of the two branches of the external carotid a. It is deep to the parotid gland and ascends posterior to the neck of the mandible and superficial to the zygomatic arch to supply a large region of the scalp

Superficial Temporal v.

Joins the maxillary v. in the region of the temporomandibular joint to form the retromandibular v. which communicates with the external jugular v. before emptying into the internal jugular v. in common with the facial and lingual vv.

Path of the Superficial Temporal v.

Joins the maxillary v. to form the retromandibular v.

Posterior Fontanelle

Lies in the median plane at the junction of the occipital and parietal bones. Closes 2-3 months after birth with the formation of the lambdoid suture

Anterior Fontanelle

Lies in the median plane, at the junctions of the frontal and parietal bones. It closes between 1.5 to 2 years.

Paired Bones of the Skull

Maxillae Palatine Nasals Inferior connchae Lacrimals Zygomatics Temporals Parietals

Infections of the Scalp

May pass to the venous sinuses of the dura mater via emissary vv. which pass through the parietal foramina to the superior sagittal sinus and other intracranial venous sinuses. Scalp lesions and facial infections can result in meningitis

Branches of the Mandibular n.

- Inferior alveolar n: enters the mandible at the mandibular foramen and exits through the mental foramen as the mental n. - Lingual n: receives general somatic sensation from the mucous membrane of the anterior 2/3 of the tongue

Layers of the Scalp

Has 5 layers, remembered with the acronym SCALP; - Skin - Connective tissue layer: highly vascularized tissue - Aponeurosis: continuous anteriorly from frontalis m. and posteriorly from occipitalis m., collectively known as occipitofrontalis m., innervated by facial n. - Loose subaponeurotic connective tissue: allows movement of the epicranial aponeurosis - Periosteum: pericranium

Neurocranium

Houses the brain, including the anatomical apparatus for hearing and vestibular finction