lecture 40 - face & scalp

THE FACE AND SCALP

The Face and scalp

The face is simply defined as that part of the head seen in a frontal view, everything between the chin and the hairline and anterior to the ears.

Muscles of Facial Expression

The muscles of facial expression constitute a large group of subcutaneous skeletal muscles underlying the skin of the face. These muscles are used to produce facial expressions that are important in nonverbal communication in humans and other primates. Some of these muscles originate from the bones of the facial skeleton and some from the skin. All insert into and move the skin. The muscles of facial expression are usually grouped into muscles of the nose, scalp and auricle, muscles around the eye, muscles around the mouth and the platysma. The muscles of facial expression develop from the second branchial arch and all are innervated by the seventh cranial nerve or facial nerve. Due to the fact that these muscles also include muscles of the cheeks, lips and eyelids, some muscles of facial expression also function in mastication, vocalization, respiration and vision. These latter multifunction muscles are the only ones that will be considered in detail.


MuscleOriginInsertionActionsInnervation

Orbicularis Oculimedial margin of orbit ( frontal and maxillary bones) and medial palpebral ligament and lacrimal boneeyelid, zygomatic bone via lateral palpebral ligamentstrong closure of the eyelidsfacial nerve (CN VII)

Orbicularis Orismaxilla and mandible and deep aspect of skinmucous membrane of lipssphincter of the oral opening, compresses and purses lips

Buccinatoralveolar processes of mandible and maxilla, pterygoman-dibular raphe

orbicularis oris and lipstenses the cheek, compresses food against the molars and functions with the pharynx during swallowing


MuscleOriginInsertionActionsInnervation

Occipito-frontalisfrontal belly from the anterior margin of the galea aponeuroticaoccipital belly from the highest nuchal linefrontal belly into the skin of root of the nose and eyebrow, occipital belly into the post. margin of the galea aponeuroticamoves scalp and raises eyebrows as in surprisefacial nerve (CN VII)

Eyelids (Palpebrae)

The eyelids or palpebrae serve to protect the eyes from injury, the retina from excessive light and to keep the cornea moist. The upper eyelid is larger and more mobile than the lower eyelid. Both the upper and lower eyelids are covered externally by thin skin and internally by palpebral conjunctiva which is continuous with conjunctiva on the eyeball and cornea, the bulbar conjunctiva. The margins of the eyelids are marked by rows of short hairs called eyelashes, cilia with large sebaceous glands, ciliary glands at their roots.

Each eyelid is given structure by a band of dense connective tissue called a tarsal plate or tarsus. The tarsal plates are anchored to the orbital rim at their lateral and medial ends by lateral and medial palpebral ligaments. In addition the outer margins of the plates are attached to the orbital septum which attaches to the entire margin of the orbital rim and closes off anterior entry into the orbit. Between the tarsal plates and the skin is a circular layer of skeletal muscle fibers, the orbicularis oculi, which functions to close the eyelids like a sphincter. The tarsal plates also have sebaceous glands (tarsal glands) embedded in them which lubricate the edges of the eyelids.

In addition to the orbicularis oculi muscle, the upper eyelid has additional muscle fibers, the levator palpebrae superioris. This skeletal muscle originates from the roof of the orbit and the fibers pass into the upper eyelid and insert into the skin. In addition there is a small group of smooth muscle fibers, the superior tarsal muscle, on the deep surface of the levator palpebrae muscle. These smooth muscle fibers insert into the superior tarsus. Both of these muscles elevate the upper eyelid (open the eye) and are working continuously as long as your eyes are open. Remember the orbicularis oculi muscle is innervated by the facial nerve (CN VII), the levator palpebrae superioris by the oculomotor nerve (CN III) and the superior tarsal muscle by sympathetic fibers conveyed all the way from the superior cervical ganglion of the neck. There is also a inferior tarsal muscle attached to the fascia of the inferior rectus muscle and inserting into the inferior tarsus that helps depress the lower eyelid, innervation is also sympathetic.The angle formed where one eyelid meets the other is called an angle or canthus. Each eye has a medial and lateral canthus. The lateral canthus is unremarkable, but the medial canthus is marked by interesting structure as well as anatomy important to the health of the eye. The epicanthic fold of certain Asian races is an extra fold of skin in the upper eyelid at the medial canthus. If you evert your upper and lower eyelids slightly you will see a small dark pit at the medial end of each margin. Each of these pits is a lacrimal punctatum and they mark the openings of lacrimal canals. The lacrimal punctata suction up tears and the canals convey them to the lacrimal sac which sits in the mouth of the nasolacrimal canal (lacrimal bone), the nasolacrimal canal conveys the tears to the nasal cavity.

Lacrimal (Tear) GlandThe lacrimal gland is composed of two parts, the larger of which is located within the orbit at the superolateral corner. The smaller part is located within the superolateral part of the upper eyelid. These glands produce both serous and oily secretions. The gland opens onto the conjunctiva via several ducts which perforate the conjunctiva where it reflects (the fornix) from the eyeball to the deep side of the upper eyelid. Each time the eye blinks, tears are spread over the eyeball by the eyelids acting like squeegees. At the same time the tears already on the eyeball which have collected dust are 'squeegeed' to the medial canthus where they are collected by the lacrimal punctata and conveyed by the lacrimal canals to the lacrimal sac. When you cry, the drainage system is overwhelmed and tears spill out of the eyes and you may taste the tears draining into the nasal cavity. The lacrimal glands are innervated by parasympathetic fibers conveyed by the facial nerve (CNVII) via the pterygopalatine ganglion.

External Nose

The external nose is more or less a pyramidal shaped structure. The free end is the tip or apex of the nose. The superior base angle is the root of the nose which is continuous with the forehead at the glabella. The other two base angles are inferior and lateral where there are two openings, the external nares or nostrils separated by a cartilaginous septum. In addition to the cartilaginous septum the external nose is supported by several other cartilages. The relatively minor bony part of the external nose is found at the root where the nasal bones and small parts of the frontal and maxillary bones form the bridge.

The Scalp

The scalp begins anteriorly at the supraorbital ridges (thus the scalp and face share the forehead) and continues posteriorly to the external occipital protuberance and highest nuchal lines. It extends laterally to the temporal lines. It is composed of five layers (SCALP). The first three layers of the scalp do not readily separate and when the scalp is torn loose (scalping) they go as a unit.

"S"kin no real difference except a lot of hair follicles.

Dense "C"onnective Tissue nerves, arteries and veins course in this layer.

"A"poneurosis consists of occipitofrontalis muscles and their intervening aponeurosis, the galea aponeurotica these muscles move scalp - innervated by the facial nerve.

"L"oose Connective Tissue separates the aponeurosis from the covering of the skull bones.

"P"ericranium external periosteum of the skull bones.

vascularization of the Face and scalp

The blood supply to the face and scalp is primarily supplied by branches of the external carotid artery with some contributions by the internal carotid artery.

arteries of the face and scalp

ArteryOriginCourseDistribution

Facialexternal carotid artery in the neck

ascends deep to submandibular gland, winds around inferior border of mandible at the anterior margin of the masseter, enters the face and ascends to corner of mouth then along lateral aspect of nose to end near medial canthus of the eyemuscles of facial expression and other facial structures via several branches

arteries of the face and scalp (cont.)


Inferior Labial A.facial artery near corner of mouth

penetrates the orbicularis oris and courses medially to anastomose with its contralateral fellow

skin, mucous membranes and muscles of lower lip and adjacent parts of the chin

Superior Labial A.

skin, mucous membranes and muscles of upper lip and adjacent parts of the nose

Lateral Nasal A.facial artery at lateral aspect of nose

courses medially to anastomose with its contralateral fellowala and dorsum of nose

Angular A.terminal branch of facial artery

ascends to medial canthus of eye to anastomose with palpebral branches of the ophthalmic artery

note: the ophthalmic artery is a branch of the internal carotid arterylower eyelid and superior aspect of cheek

Superficial Temporal A.terminal branch of external carotid artery arising within the parotid gland posterior to neck of mandible

ascends anterior to ear to temporal region ending in the scalp

parotid gland, TMJ, masseter and temporalis muscles, the auricle, the lateral scalp and the skin overlying the above structures, anastomoses with its contralateral fellow across the midline of the scalp and with the occipital artery posteriorly



Transverse Facial A.superficial temporal artery within the parotid gland

courses medially superficial to masseter and inferior to zygomatic archparotid gland, duct and skin and facial muscles in the area

Posterior Auricular A.arises from external carotid artery in the neck

courses posterosuperiorly deep to parotid gland to end by branching between the auricle and the mastoid processauricle and the scalp behind the ear

Occipital A.arises from external carotid artery in the neck

courses posterosuperiorly and runs in the occipital groove of the temporal bone, ascends deep to several muscles attaching to the occipital skull finally piercing the fascial attachments of the SCM and trapezius to the skull to branch and end in the posterior scalp - accompanied in much of its course by the greater occipital nerveposterior scalp anteriorly to the vertex and many of the structures it pierces

Mental A.(L. mentum, chin)terminal branch of inferior alveolar artery

exits from mental foramen of mandible facial muscle and skin of chin



Infraorbital A.maxillary arteryexits from infraorbital foramen of maxillae

facial muscles, lacrimal sac. lower eyelid, cheek and upper lip

Supraorbital A.terminal branch of ophthalmic artery in the orbit

exits the orbit through the supraorbital foramen or notch of the frontal bone to enter the forehead - anastomoses with branches of the superficial temporal and occipital arteriesupper eyelid, muscles and forehead and scalp posteriorly to vertex

Supratrochlear A.terminal branch of ophthalmic artery in the orbitexits the orbit medial to the supraorbital arteryupper eyelid and forehead

Veins

The veins of the face and scalp are of more than passing interest due to their connections to the venous system within the skull and the fact that they have no valves and thus blood flow in them can change direction depending on local conditions. The supratrochlear and supraorbital veins join to form the angular vein that in turn becomes the facial vein draining the structures supplied by the facial artery.

The supratrochlear and supraorbital veins are in turn connected to ophthalmic veins that course through the orbits into the skull to empty into the cavernous venous sinus. The occipital and superficial temporal veins begin as widespread plexuses of veins in the scalp. These scalp veins are also connected to emissary veins that penetrate the skull bone to empty into the venous sinuses of the skull.

Innervation of the Face and scalp

The sensory innervation of the face and anterior scalp is provided entirely by branches of the trigeminal nerve, the fifth cranial nerve and the motor innervation is supplied entirely by branches of the facial nerve, the sixth cranial nerve.

nerves of the face and scalp

NerveOriginCourseDistribution

Facial N.brainstemexits from stylomastoid foramen, courses anteriorly to enter parotid gland, dividing into several branches within which traverse gland to exit and supply facemotor fibers to facial and scalp muscles

nerves of the face and scalp (cont.)


Ophthalmic Division of the Trigeminal Nerve or Ophthalmic Nerve (V1)arises from the trigeminal ganglion

exits from the middle cranial fossa into the orbit via the superior orbital fissure, divides into lacrimal, frontal and nasociliary branches in the orbit

all branches are sensory - nose, forehead, upper eyelids including the conjunctiva and bulbar conjunctiva and scalp posteriorly to vertex certain branches conduct secretomotor fibers derived from other sources

Frontal N.ophthalmic nerve passes into orbit via superior orbital fissure - courses anteriorly on levator palpebrae m.divides into supraorbital and supratrochlear brs.

Nasociliary N.passes into orbit via superior orbital fissure -crosses optic n. with ophthalmic a. deep to superior rectus m. to medial side of orbitbranches sensory to skin of dorsum and tip of nose and skin and conjunctiva of upper eyelid

Lacrimal N.passes into orbit via superior orbital fissure - courses along superior border of lateral rectus m. with lacrimal a.sensory to skin and conjunctiva of upper eyelid



Supraorbital N.frontal nerve

exits orbit via supraorbital foramen or notch to enter foreheadcutaneous to skin of upper eyelid, forehead and scalp posteriorly to vertex

Supratrochlear N.exits orbit medial to supraorbital nervecutaneous to upper eyelid and central forehead

Maxillary Division of the Trigeminal Nerve or the Maxillary Nerve (V2)arises from the trigeminal ganglion

exits from the middle cranial fossa into the pterygopalatine fossa via the foramen rotundumall branches are sensory - lower eyelid including conjunctiva, alae of nose, upper lip, cheeks and anterior temporal region

Infraorbital N.direct continuation of the maxillary nervecourses through floor of orbit in infraorbital groove and exits from the infraorbital foramen into the face

branches are cutaneous to lower eyelid including the conjunctiva, side of nose and upper lip

Zygomatico-temporal N.zygomatic nerve

(a branch of the maxillary nerve, within the orbit)

passes through zygomatic bone and exits from zygomatico-temporal foramencutaneous to anterior temple region

Zygomaticofacial N.passes through zygomatic bone and exits from zygomaticofacial foramencutaneous to skin over cheek bone



Mandibular Division of the Trigeminal Nerve or the Mandibular Nerve (V3)arises from the trigeminal ganglion

exits from the middle cranial fossa into the infratemporal fossa via the foramen ovale

cutaneous to lower lip, chin, skin over the mandible, anterosuperior part of auricle and lateral aspect of face anterosuperior to ear and adjacent scalp

Inferior Alveolar N.mandibular nervecourses inferiorly to enter mandibular canalteeth of lower jaw and adjacent gums - ends as mental n.

Auriculotemporal N.arises by two roots from the mandibular nerve in the infratemporal fossa - roots pass around the middle meningeal artery and fuse into a single nerveexits from the infratemporal fossa by passing through the parotid gland and ascending between the neck of the mandible and the external acoustic meatuscutaneous to anterosuperior aspect of auricle, skin of face anterior to ear and posterior temporal region and adjacent scalp

Buccal N.arises from the mandibular nerve in the infratemporal fossacourses anteriorly and laterally to reach the skin of the cheekcutaneous to cheek overlying the buccinator muscle - sensory to mucosa inside cheek and adjacent gingiva

Mental N.terminal branch of inferior alveolar nerve exits mental foramen into the chincutaneous to lower lip and chin - mucosa inside lip and adjacent gingiva



Great Auricular N.ventral rami of C2 and C3 (part of cervical plexus)winds around posterior border of scm. muscle and ascends obliquely across muscle into parotid gland and divides into several branchescutaneous to skin over parotid gland and mastoid region and front and back of lower part of auricle

Lesser Occipitalventral ramus of C2 (part of cervical plexus)

ascends along the posterior border of the scm. muscle to the region posterior to the earcutaneous to skin behind the ear and on the posterior aspect of the auricle

Greater Occipital see nerves of the Suboccipital Region

Third Occipital

Lymphatic Drainage

The lymphatic drainage of the face and scalp is to nodes located in the following regions. The nodes are sensitive to infections and diseases in the region and are easily palpated by a physician.

Occipital

Mastoid

Parotid

Buccal

Submental

Submandibular

Superficial CervicalParotid Gland

The parotid gland is the largest salivary gland. It is enclosed within a tough fascial sheath and sits within a space called the parotid bed. The parotid bed is anterior and inferior to the external acoustic meatus and squeezed between the mastoid process and the mandibular ramus. The parotid gland extends inferiorly as far as the angle of the mandible. The parotid gland drains via the parotid duct which is about 5 cm long. The parotid duct leaves the anterior aspect of the gland, passes across the upper part of the masseter muscle. At the anterior edge of the masseter muscle the duct turns sharply medially, pierces the buccinator muscle and opens into buccal cavity just opposite the crown of the second upper molar tooth.The parasympathetic innervation to the parotid gland is by the glossopharyngeal nerve (CN IX) via the otic ganglion. Sympathetic fibers reach the gland via the nerve plexus associated with the external carotid artery.

Structures Associated With The Parotid Gland

Because of its size and location, the parotid gland is associated with several very important structures, some of which travel through the gland and even divide within it. Due to the fascia associated with the gland, dissection of this area, either surgically or in the lab, is an arduous and painstaking process.

Facial Nerve (CN VII) See description under Nerves of the Face and Scalp.

Retromandibular Vein the retromandibular vein is formed by the union of the superficial temporal and maxillary veins descends in the parotid gland picking up drainage from the gland passes out of the inferior aspect of the gland to pick up a branch of the facial vein joins the posterior auricular vein to form the external jugular vein.

The External Carotid Artery enters the deep aspect of the parotid gland and ascends to the level of the neck of the mandible where it divides into its two terminal branches: the superficial temporal artery and the maxillary artery.

Clinical Note: Damage to the cervical sympathetic trunk will result in paralysis or paresis of the superior tarsal muscle and a drooping of the eyelid (ptosis). This is one symptom of a condition called Horner's syndrome. Damage to the oculomotor nerve or its motor nucleus will result in paralysis of the levator palpebrae superioris and an inability to voluntarily open the eyes.

Clinical Note: Lacerations to dense connective tissue layer tend to gap and hold open the cut vessels and bleeding is profuse. Bleeding to death is a possibility for severe wounds and an unconscious victim.

Clinical Note: The loose connective tissue layer is often the site of infections which spread rapidly due to looseness of connective tissue.

Clinical Note:

Triangle of Danger

Because of the lack of valves in the facial vein and its connections to the venous sinuses of the skull, the drainage territory of the facial vein is considered to be an area of concern. This area roughly forms a triangle with the apex at the root of the nose and the base along the upper lip; this is the so-called triangle of danger. Infections in this area have the possibility of traveling into the venous sinuses of the skull rather than draining into the normal external jugular system. The source of infection can be anything in the area including infected pimples.

Scalp Infections

In a similar manner infections of the scalp may drain via emissary veins into the venous sinuses of the skull.

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lecture 40 - face & scalp

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