Anatomy of face lecture notes for dissection

 Anatomy of face  

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Extension of face: it extends from the superior margin of the forehead to the chin, and from one ear to another ear. 

Characteristic features of skin of face are:

§  It is highly vascular and elastic.

§  It contains large number of sweat and sebaceous glands (is common site for acne).

§  It is lax except on nose where it is attached to the underlying cartilages (laxity of the skin facilitates rapid spread of edema).

§  Melanocytes, cells responsible for producing melanin, determine the skin color and pigmentation. The face may have variations in pigmentation due to sun exposure, hormonal changes, or skin conditions

§  Facial skin is often more sensitive compared to skin on other parts of the body,

§   It provides insertion to the muscles of facial expression.

Superficial Fascia of face

It receive insertion of muscles of facial expression. It contain blood vessels and nerves and varying amount of fat. The fat is absent in the eyelids, however it is abundant in cheeks (especially in children) and is called buccal pad of fat.

Deep fascia of face  : It is absent in face except over the parotid gland and masseter muscle (parotido-masseteric fascia).The absence of deep fascia in the face allows facial expressions to be seen.  Lack of a deep fascial layer is also responsible for rapid fluid accumulation after injury or water retention due to heart or kidney failure.

Sensory innervation of face:

Skin of face is supplied by the three divisions of trigeminal nerve i.e. ophthalmic, maxillary and mandibular. A small part over the angle of mandible is supplied by great auricular nerve ( from ventral rami of C2,C3 spinal nerves).

Face can be roughly divided into three regions with respect to sensory innervation – upper1/3rd, middle 1/3rd and lower 1/3rd and is mainly supplied by the three divisions of trigeminal nerve i.e. ophthalmic, maxillary and mandibular nerves.

• The upper one-third  of face develops from the frontonasal process and is supplied by branches of ophthalmic nerve.
• The middle third of face develops from maxillary processes and is supplied by branches of maxillary nerve.
• The lower third of face develops from mandibular processes and is supplied by branches of mandibular nerve.

However, the areas of cutaneous innervation aren’t horizontal, but extend in the posterosuperior direction corresponding to the direction of development of head and brain. Part of the neck skin is drawn up to overlap the angle of the mandible. This part of the skin is therefore supplied by great auricular (C2).

The branches of the three divisions of trigeminal nerve that supply the skin of face are as follows:

Branches of ophthalmic division of trigeminal nerve

1. Supraorbital
2. Supratrochlear
3. Lacrimal
4. Infratrochlear
5. External nasal

Branches of maxillary division of trigeminal nerve:

1. Infraorbital
2. Zygomaticofacial
3. Zygomaticotemporal

Branches of mandibular division of trigeminal nerve:

1. Mental
2. Buccal
3. Auriculotemporal

Motor innervation of face

The muscles of face are supplied by the facial nerve. Facial nerve leaves the cranial cavity via stylomastoid foramen, it wind around the lateral aspect of styloid process and enters the parotid gland. Within the parotid gland it gives 5 terminal branches viz.

• temporal
• zygomatic
• buccal
• marginal mandibular
• cervical

The branches emerge along the anterior border of the parotid gland and supply the muscles of facial expression. 

 

BRANCHES OF FACIAL NERVE	MUSCLES SUPPLIED
Temporal branch	Frontalis
	Orbicularis oculi
	Corrugator supercilii
Zygomatic branch	Orbicularis oculi
Buccal branches	Zygomaticus major and minor
Upper buccal branch	Levator labii superioris alaeque nasi.
	Muscles of the nose
	Levator anguli oris
	Levator labii superioris
Lower buccal branch	Buccinator
	Orbicularis oris
Marginal mandibular branch	Risorius.
	Depressor anguli oris
	Depressor labii inferioris
	Mentalis
Cervical branch	Platysma

What are the special features of muscles of facial expression ?

• The muscles of facial expression are present in the superficial fascia of the face.
• Most of them take origin from bones of facial skeleton and are inserted into the skin.
• Morphologically, they represent the subcutaneous muscle (panniculus carnosus) present in some animals.
• Embryologically, they arise from the mesoderm of second pharyngeal/branchial arch and are  therefore supplied by cranial nerve,  facial nerve, the nerve of second arch.
• Functionally, they are arranged around three orifices palpebral fissure, nostrils and mouth and are responsible for  their closure (sphincters) of opening (dilators).
• They are also responsible for facial expressions. 

Bell’s palsy

It is lower motor neuron type paralysis of facial muscles which occurs because of compression of facial nerve in the facial canal near stylomastoid foramen. It results in ipsilateral paralysis of facial muscles. The symptoms of Bell’s palsy include:

Facial asymmetry because of unopposed muscular contraction of normal side.Loss of horizontal wrinkles on forehead because of paralysis of frontalis muscle.  Inability to close the eyes and widening of palpebral fissure because of paralysis of orbicularis oculi. Loss of corneal reflex (efferent limb of the reflex is formed by facial nerve). Drooling of saliva from corner of mouth because of paralysis of orbicularis oris, muscles of facial expression . Absence of nasolabial fold because of paralysis of levator labii superioris alaeque nasi, muscles of facial expression.

Epiphora (tears flow down from the eye) because of paralysis of the lower part of the orbicularis oculi.

When the person tries to smile the angle of mouth of the normal side moves upwards and laterally. Accumulation of food into the vestibule of mouth because of paralysis of buccinator muscle.

• Why Facial plastic surgery is mostly successful
• As skin of the face has very rich blood supply, it is uncommon in plastic surgery for skin flaps to necrose.
• Why does edema on the face spread quickly owing to water retention in the body caused by heart and kidney failure?
• The laxity of skin over most of the parts of face allows fast spread of edema in the region of the face.
• Why face is common site for acne?
• It is due to the presence of large number of sebaceous glands in this region.
•  What is Ectropion and Epiphora?
• Paralysis of orbicularis oculi leads to drooping of the lower eyelid called ectropion, which causes spilling of tear on the cheek (Epiphora).
•  What happens in case of paralysis of buccinator muscle?
• Paralysis of buccinator muscle (in facial palsy – injury to facial nerve, lower motor type of paralysis), food tends to accumulate in the vestibule of mouth and the person is unable to blow and whistle.