Anatomy

Human Anatomy

The Scalp
Structure
The scalp consists of five layers, the first three of which are intimately bound together and move as a unit.
1. Skin, which is thick and hair bearing and contains
numerous sebaceous glands
2. Connective tissue beneath the skin, which is fibrofatty, the fibrous septa uniting the skin to the underlying aponeurosis of the occipitofrontalis muscle. Numerous arteries and veins are found in this layer. The arteries are branches of the external and internal carotid arteries, and a free anastomosis takes place between them.

3. Aponeurosis (epicranial), which is a thin, tendinous sheet that unites the occipital and frontal bellies of the occipitofrontalis muscle. The lateral margins of the aponeurosis are attached to the temporal fascia. The subaponeurotic space is the potential space beneath the epicranial aponeurosis. It is limited in front and behind by the origins of the occipitofrontalis muscle, and it extends laterally as far as the attachment of the aponeurosis to the temporal fascia.
4. Loose areolar tissue, which occupies the subaponeurotic space and loosely connects the epicranial aponeurosis to the periosteum of the skull (the pericranium). The areolar tissue contains a few small arteries, but it also contains some important emissary veins. The emissary veins are valveless and connect the superficial veins of the scalp with the diploic veins of the skull bones and with the intracranial venous sinuses.
5. Pericranium, which is the periosteum covering the outer surface of the skull bones.

Muscles of the Scalp

Occipitofrontalis muscle: when this muscle contracts, the first three layers of the scalp move forward or backward, the loose areolar tissue of the fourth layer of the scalp allowing the aponeurosis to move on the pericranium. The frontal bellies of the occipitofrontalis can raise the eyebrows in expressions of surprise or horror.
Origin:
Occipital belly: Highest nuchal line of occipital bone.
Frontal belly: Skin and superficial fascia of eyebrows.
Insertion: Epicranial aponeurosis.
Nerve Supply: Facial nerve.
Action: Moves scalp on skull and raises eyebrows

Sensory Nerve Supply of the Scalp

The main trunks of the sensory nerves lie in the superficial
fascia. Moving laterally from the midline anteriorly, the following
nerves are present:
1. supratrochlear nerve, a branch of the ophthalmic division of the trigeminal nerve, winds around the superior orbital margin and supplies the scalp. It passes backward close to the median plane and reaches nearly as far as the vertex of the skull.
2. supraorbital nerve, a branch of the ophthalmic division of the trigeminal nerve, winds around the superior orbital margin and ascends over the forehead. It supplies the scalp as far backward as the vertex.
3. zygomaticotemporal nerve, a branch of the maxillary division of the trigeminal nerve, supplies the scalp over the temple.

4. Auriculotemporal nerve, a branch of the mandibular division of the trigeminal nerve, ascends over the side of the head from in front of the auricle. Its terminal branches supply the skin over the temporal region.
5. Lesser occipital nerve, a branch of the cervical plexus (C2), supplies the scalp over the lateral part of the occipital region and the skin over the medial surface of the auricle.
6. Greater occipital nerve, a branch of the posterior ramus of the 2nd cervical nerve, ascends over the back of the scalp and supplies the skin as far forward as the vertex of the skull

Arterial Supply of the Scalp

The scalp has a rich supply of blood to nourish the hair follicles, and, for this reason, the smallest cut bleeds profusely. The arteries lie in the superficial fascia. Moving laterally from the midline anteriorly, the following arteries are present:
1. Supratrochlear and Supraorbital arteries, branches of the ophthalmic artery, ascend over the forehead in company with the supratrochlear and supraorbital nerves.

2. Superficial temporal artery, the smaller terminal branch of the external carotid artery, ascends in front of the auricle in company with the auriculotemporal nerve. It divides into anterior and posterior branches, which supply the skin over the frontal and temporal regions.
3. Posterior auricular artery, a branch of the external carotid artery, ascends behind the auricle to supply the scalp above and behind the auricle.
4. Occipital artery, a branch of the external carotid artery, ascends from the apex of the posterior triangle, in company with the greater occipital nerve. It supplies the skin over the back of the scalp and reaches as high as the vertex of the skull.

Venous Drainage of the Scalp

The supratrochlear and supraorbital veins unite at the medial margin of the orbit to form the facial vein.
The superficial temporal vein unites with the maxillary vein in the substance of the parotid gland to form the retromandibular vein.
The posterior auricular vein unites with the posterior division of the retromandibular vein, just below the parotid gland, to form the external jugular vein.
The occipital vein drains into the suboccipital venous plexus, which lies beneath the floor of the upper part of the posterior triangle; the plexus in turn drains into the vertebral veins or the internal jugular vein.
The veins of the scalp freely anastomose with one another and are connected to the diploic veins of the skull bones and the intracranial venous sinuses by the valveless emissary veins

Lymph Drainage of the Scalp

Lymph vessels in the anterior part of the scalp and forehead drain into the submandibular lymph nodes. Drainage from the lateral part of the scalp above the ear is into the superficial parotid (preauricular) nodes; lymph vessels in the part of the scalp above and behind the ear drain into the mastoid nodes. Vessels in the back of the scalp drain into the occipital nodes.

The Face

Skin of the Face
The skin of the face possesses numerous sweat and sebaceous glands. It is connected to the underlying bones by loose connective tissue, in which are embedded the muscles of facial expression. No deep fascia is present in the face.

Sensory Nerves of the Face

The skin of the face is supplied by branches of the three divisions of the trigeminal nerve, except for the small area over the angle of the mandible and the parotid gland , which is supplied by the greater auricular nerve (C2 and 3).

A. Ophthalmic Nerve

The ophthalmic nerve supplies the skin of the forehead,
the upper eyelid, the conjunctiva, and the side of the nose down to and including the tip. Five branches of the nerve pass to the skin.
1. Lacrimal nerve supplies the skin and conjunctiva of the lateral part of the upper eyelid .
2. Supraorbital nerve winds around the upper margin of the orbit at the supraorbital notch. It divides into braches that supply the skin and conjunctiva on the central part of the upper eyelid; it also supplies the skin of the forehead.

3. Supratrochlear nerve winds around the upper margin of the orbit medial to the supraorbital nerve . It divides into branches that supply the skin and conjunctiva on the medial part of the upper eyelid and the skin over the lower part of the forehead, close to the median plane.
4. Infratrochlear nerve leaves the orbit below the pulley of the superior oblique muscle. It supplies the skin and conjunctiva on the medial part of the upper eyelid and the adjoining part of the side of the nose.
5. External nasal nerve leaves the nose by emerging between the nasal bone and the upper nasal cartilage. It supplies the skin on the side of the nose down as far as the tip


B. Maxillary Nerve
The maxillary nerve supplies the skin on the posterior part of the side of the nose, the lower eyelid, the cheek, the upper lip, and the lateral side of the orbital opening. Three branches of the nerve pass to the skin.
■■ Infraorbital nerve is a direct continuation of the maxillary nerve. It enters the orbit and appears on the face through the infraorbital foramen. It immediately divides into numerous small branches, which radiate out from the foramen and supply the skin of the lower eyelid and cheek, the side of the nose, and the upper lip.
■■ Zygomaticofacial nerve passes onto the face through a small foramen on the lateral side of the zygomatic bone. It supplies the skin over the prominence of the cheek.
■■ Zygomaticotemporal nerve emerges in the temporal fossa through a small foramen on the posterior surface of the zygomatic bone. It supplies the skin over the temple.

C. Mandibular Nerve

The mandibular nerve supplies the skin of the lower lip, the lower part of the face, the temporal region, and part of the auricle. It then passes upward to the side of the scalp. Three branches of the nerve pass to the skin.
■■ Mental nerve emerges from the mental foramen of the mandible and supplies the skin of the lower lip and chin.
■■ Buccal nerve emerges from beneath the anterior border of the masseter muscle and supplies the skin over a small area of the cheek.
■■ Auriculotemporal nerve ascends from the upper border of the parotid gland between the superficial temporal vessels and the auricle. It supplies the skin of the auricle, the external auditory meatus, the outer surface of the tympanic membrane, and the skin of the scalp above the auricle

Arterial Supply of the Face

The face receives a rich blood supply from 3 main vessels: the facial artery, superficial temporal artery and ophthalmic arteries, which are supplemented by several small arteries that accompany the sensory nerves of the face. The facial artery arises from the external carotid artery. Having arched upward and over the submandibular salivary gland, it curves around the inferior margin of the body of the mandible at the anterior border of the masseter muscle. It is here that the pulse can be easily felt. It runs upward in a tortuous course toward the angle of the mouth and is covered by the platysma and the risorius muscles. It then ascends deep to the zygomaticus muscles and the levator labii superioris muscle and runs along the side of the nose to the medial angle of the eye, where it anastomoses with the terminal branches of the ophthalmic artery.

A. facial artery: which has 4 branches on the face

1. The submental artery arises from the facial artery at the lower border of the body of the mandible. It supplies the skin of the chin and lower lip.
2. The inferior labial artery arises near the angle of the mouth. It runs medially in the lower lip and anastomoses with its fellow of the opposite side.
3. The superior labial artery arises near the angle of the mouth. It runs medially in the upper lip and gives
branches to the septum and ala of the nose.
4. The lateral nasal artery arises from the facial artery
alongside the nose. It supplies the skin on the side and
dorsum of the nose.
Finally the facial artery ends at the medial angle of the eye as Angular artery which supply


B. Superficial temporal artery , the smaller terminal branch of the external carotid artery, commences in the parotid gland. It ascends in front of the auricle to supply the scalp.
-The transverse facial artery, a branch of the superficial temporal artery, arises within the parotid gland. It runs forward across the cheek just above the parotid duct.
c. Ophthalmic artery: has 2 branches which are the supraorbital and supratrochlear arteries which supply the skin of the forehead.
D. Maxillary artery: gives 1 branch on the face which is Infraorbital artery .

Superficial temporal artery

Supraorbital artery
Supratrochlear artery
Facial artery
Infraorbital artery

Venous Drainage of the Face

The facial vein is formed at the medial angle of the eye by the union of the supraorbital and supratrochlear veins. It is connected to the superior ophthalmic vein directly through the supraorbital vein. By means of the superior ophthalmic vein, the facial vein is connected to the cavernous sinus; this connection is of great clinical importance because it provides a pathway for the spread of infection from the face to the cavernous sinus. The facial vein descends behind the facial artery to the lower margin of the body of the mandible. It crosses superficial to the submandibular gland and is joined by the anterior division of the retromandibular vein. The facial vein ends by draining into the internal jugular vein.

Tributaries

The veins to be seen in the face and parotid region are the facial vein, the superficial temporal vein, and the retromandibular vein. The retromandibular vein is formed within the upper part of the parotid gland by the union of the superficial temporal and maxillary veins. Its lower end divides, within the gland, into anterior and posterior divisions that emerge from the gland near its lower end. The posterior division, that is the main continuation of the retromandibular vein, joins the posterior auricular vein to form the external jugular vein. The anterior division joins the facial vein to form the common facial vein.
The facial vein runs downwards and backwards just behind the facial artery, and receives tributaries corresponding to branches of the artery. It ends by joining the anterior division of the retromandibular vein to form the common facial vein. The common facial vein ends in the internal jugular vein.

Muscles of the Face (Muscles of Facial Expression)

The muscles of the face are embedded in the superficial fascia, and most arise from the bones of the skull and are inserted into the skin. The orifices of the face, namely, the orbit, nose, and mouth, are guarded by the eyelids, nostrils, and lips, respectively. It is the function of the facial muscles to serve as sphincters or dilators of these structures. A secondary function of the facial muscles is to modify the expression of the face. All the muscles of the face are developed from the second pharyngeal arch and are supplied by the facial nerve.

Muscles of the Eyelids

The sphincter muscle of the eyelids is the orbicularis oculi.
Muscles of the Nostrils
The sphincter muscle is the compressor naris and the dilator muscle is the dilator naris.
Muscles of the Lips and Cheeks
The sphincter muscle is the orbicularis oris. The dilator muscles consist of a series of small muscles that radiate out from the lips.
Example of the muscle of the check is Buccinator m.

Facial Nerve

As the facial nerve runs forward within the substance of the parotid salivary gland , it divides into its five terminal branches.
■■ The temporal branch emerges from the upper border of the gland and supplies the anterior and superior auricular muscles, the frontal belly of the occipitofrontalis, and the upper part of orbicularis oculi.
■■ The zygomatic branch emerges from the anterior border of the gland and supplies the lower part of orbicularis oculi.
■■ The buccal branch emerges from the anterior border of the gland below the parotid duct and supplies the buccinator muscle and the muscles of the upper lip and nostril.


■■ The mandibular branch emerges from the anterior border of the gland and supplies the muscles of the lower lip.
■■ The cervical branch emerges from the lower border of the gland and passes forward in the neck below the mandible to supply the platyzma muscle
The facial nerve is the nerve of the second pharyngeal arch and supplies all the muscles of facial expression. It does not supply the skin, but its branches communicate with branches of the trigeminal nerve.