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10
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THE FACIAL PART OF THE HEAD
OPERATIONS ON THE HEAD
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The border between the head and neck is the line which is drawn along the inferior margin
of the mandible, apex of the mastoid process, superior nuchal line to the external occipital
protubeÂrance and passes on to another side.
The facial part is composed of the following regions: the orbital region, the oral cavity
reÂgion (the region of the mouth), nose region (region of the nose), the lateral region and deep
region of the face. You studied the orbital region, the region of the nose, the region of the mouth
on department of normal anatomy.
The lateral region
of face is composed of the buccal region and the parotid region. The border between them passes
along the anterior margin of the masseter muscle.
The skin of the face possesses numerous sweat and sebaceous glands. It is connected to
the underlying bones by loose connectiÂve tissue, in which the muscles of facial expression are
embedÂded. There is no deep fascia in the face.
Wrinkle lines of the face result from repeated folding of the skin perpendicular to the long
axis of the underlying contÂracting muscles, coupled with the loss of youthful skin elasticiÂty.
Surgical sears of the face are less seen if they follow the wrinkle lines.
The skin of the face is supplied by branches of three divisions of the trigeminal nerve,
except for the small area over the angle of the mandible and parotid gland, which is supplied by
the great auricular nerve (C2 and C3).
The points of an outcome of sensitive branches of a trigeminal nerve project on the vertical
line which has been carried out between an internal and median third of supraorbital edge.
The ophthalmic nerve supplies the skin of the forehead by means of the terminal cutaneous
branches. They are: supraorbital nerve and supratrochlear nerve, which come out at level of
supraorbital edge.
The maxillary nerve supplies the skin of the cheek, the side of the nose, the upper lip by
means of the terminal cutaneous branch – the infraorbital nerve, which come out at level of
infraorbital edge (0,5 – 0,8 cm below it).
The mandibular nerve supplies the skin of the lower lip, the lower part of the face and small
area of the cheek by means of the terminal cutaneous branches. They are: the mental nerve and
buccal nerve, which come out at midpoint between alveolar and inferior edges of mandible.
Trigeminal neuroalgia is a relatively common condition in which the patient
experiences excruciating pain in the distribution of the mandibular or maxillary division, with the
ophthalmic division usually escaping. A physician should be able to map out accurately on a
patient's face the distributiÂon of each of the divisions of the trigeminal nerve.
The face receives a rich blood supply from two main vessels, the facial and the superficial
temporal arteries. The face and scalp have a very rich blood supply derived from the large exterÂnal carotid artery and many anastomoses of its branches across the midline. Wounds of this region
bleed freely and repair well.
The facial artery 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. From this point
it runs a tortuous course past angle of the mouth to the medial angÂle of the palpebral fissure of
the eye.
The supraorbital and supratrochlear arteries, branches of the ophthalmic artery supply
the skin of the forehead.
The blood supply to the skin of the face is profuse, so that it is rare in plastic surgery for
skin flaps to necrose in this region.
The superficial temporal artery as it crosses the zygomaÂtic arch in front of the ear and
the facial artery, as it winds around the lower margin of the mandible level with the anterior border
of the masseter, are commonly used by the anesthetist to take the patient’s pulse.
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 conÂnected to the superior ophthalmic vein directly through the
supraÂorbital vein. By means of the superior ophthalmic vein, the faciÂal vein is connected to the
cavernous sinus. This connection is of great clinical importance, since 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 subÂmandibular gland and is joined by the anterior
division of the retromandibular vein. The facial vein ends by draining into the internal jugular vein.
The facial vein receives tributaries that correspond to the branches of the facial artery. It is
joined to pterygoid venous plexus by the deep facial vein, and to the cavernous sinus by the superior
ophthalmic vein.
The area of facial skin bounded by the nose, the eye and the upper lid is a potentially
dangerous zone to have an infection. For example, a boil in this region may cauÂse thrombosis
of the facial vein with spread of organisms through the superior ophthalmic veins to the cavernous
sinus.
Another way of the spread is through the deep facial vein to the pterygoid venous plexus
and further through the inferior ophthalmic veins to the cavernous sinus or through the foramen
ovale along emissary vein to the cavernous sinus.
The resulting cavernous sinus thrombosis may be fatal unless adequately treated with
antibiotics.
The muscles of the human face lie in the subcutaneous tissue and most are attached to the
skin. The orifices of the face namely, the orbit, nose and mouth are guarded by the eyelids, nostrils
and lips. It is the function of the facial muscles to serve as sphincÂters 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 supplied by the facial nerve. The facial nerve does not
supply the skin.
Injuries to this nerve have seriÂous consequences. Socially, a facial paralysis is a severe
disability because an expressionless half of the face is paired with a grimace due to the unbalanced
contraction of the unaffected muscles of the other half. Of more importance functionally is the
inability to close the eye or blink and thus the loss of an essential protective mechanism.
Paralysis of the sphincter of the mouth leads to difficulties in eating, drinking, speaking and a
failure to control the escape of saliva.
Damage to the facial nerve in the internal acoustic meatus (by a tumor), in the middle ear
(by infection or operation), in the facial nerve canal or in the parotid gland (by a tumor) or due
to lacerations of the face will cause distortion of the face, with drooping of the lower
eyelid, and the angle of the mouth will sag on the affected side.
Parotid region
The parotid region overlies in part both the temporal and infratemporal regions and has
therefore, an intermediate position between the superficial and deep structures of the face. The
main structure within it is the parotid gland.
The parotid gland is the largest of the paired salivary glands which open into the oral
cavity. It lies wedged between the ramus of the mandible and the masseter anteriorly and the
sternocleidomastoid posteriorly and overlaps both the muscles suÂperficially.
Its deepest part is related to the posterior belly of the digastric muscle. And also note how
close its deep surface is to the internal jugular vein, internal carotid artery and the nerves
associated with them.
The superior surface of the gland is related to the cartilaginous part of the external acoustic
meatus and the temporomandibular joint and its more superficial part overlaps the zygomatic arch
above these. Superficially the gland is covered by the skin and platysma muscle and branches of
the great auricular nerve.
The superficial layer of the deep cervical fascia (parotidomasseteric fascia) divides to
enclose the whole gland in a fascial sheath which separates its lower part from the submandibular
salivary gland. The pain of acute viral parotitis or mumps is probably due to the pressure within
the sheath caused by the inflammation.
From the anterior border of the gland appears the parotid duct. This crosses the
surface of the masseter and at its anteriÂor border turns medially to pierce the buccal pad of fat
and the buccinator muscle. It opens into the oral cavity opposite the crown of the second upper
molar tooth.
The structures within the parotid gland are the facial nerÂve, the retromandibular vein,
and the external carotid artery. Some members of the parotid group of lymph nodes are also
located within the gland.
The facial nerve come out from facial canal through stylomastoid foramen into parotid
gland. Before entering the gland the facial nerve gives off the posterior auricular nerve whose
branches supply the occipital belly of occipitofrontalis, the stylohyoid muscle and the posteÂrior
belly of the digastric muscle.
The nerve then enters the paÂrotid gland and breaks up into five groups of branches which
fan out like the digits of the hand to supply the remaining muscles of the face. These branches are
named temporal, zygomatic, bucÂcal, marginal mandibular and cervical after the regions toward
which they are directed.
Branches pass from point 1,5 – 2 cm below external auditory meatus (or anteriorly and
inferiorly from tragus).
The temporal branch direct vertically upward.
The zygomatic branch passes to lateral angle of an eye.
The buccal branch direct to nostrils or to lateral angle of a mouth.
The mandibular branch passes along inferior margin of a mandible.
The cervical branch direct vertically downwards.
Of these it is the zygomatic, buccal and mandibular branches that supply the muscles
around the eye and mouth and great care must be taken not to damage them during surgical
procedures near the parotid gland. For prevention of damage of branches of a facial nerve the
incisions at purulent processes on the face should be carried out radially – on their course.
Wounds of the cheek may damage the parotid duct and it is worth knowing that this lies on
the middle third of a line drawn between the tragus of the ear and the midpoint between the nostÂril
and angle of the mouth...
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