face anatomy l General human anatomy revision for dental students

Face anatomy l General human anatomy revision for dental students

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The face

Definition:

• The face is the part of the front of the head between the ears and from the chin to the hair line.

 

Skin:

•  Elastic, very vascular and has numerous sweat and sebacious glands.
• Varies in thickness and is very thin in the eye lids.

 

Superficial fascia:

• The muscles of face are embedded in the superficial fascia.
• Contains also numerous vessels, nerves and fat.

 

Deep fascia:

• No deep fascia in the face except over  parotid gland and over Buccinator muscle.

 

Muscles of face:

Characteristics:

• They are embedded in the superfascial fascia.
• The majority arise from the bones of the skull and inserted into the skin.
• They arrange themselves around the orifices of the face, namely, the orbit, nose, mouth as two groups:

1. Sphincter group                   
2. Dilator group

• They modify the expression of the face as secondary function hence the name "muscles of facial expression".
• They developed from the 2^nd pharyngeal arch (mesoderm of it) so they are supplied by facial nerve (7^th cranial nerve).

 

Muscles of eye lids:

• Orbicularis oculi.                          
• Curregator supercilli.

 

Muscles of nose trills:

1. Compressor naris                
2. Dilator naris
3. Procerus           
4. Levator labii superioris alaeque nasi

 

Muscles of lips and cheeks:

• Orbicularis  oris                             
• Buccinator (muscle of cheek)
• Dilator muscles of the lips, many small see to the figure below.

Orbicularis occuli muscle:

• It is the sphincter of the eye.
• It consists of three parts     

1. Orbital      
2. Palpebral   
3. Lacrimal

 

Orbital part:

1. The outer thickest part of the muscle that surrounds the orbital margin.
2. Origin: the upper border of the med. of palpebral lig. The fibers then curve around the orbital margin.
3. Insertion: into the lower border of the med. palpeblar ligament

• N.B: the med. palpebral ligament extends from the medial angle of the eye to the nasal bone. 

    The palpebral part:

• Lies in the substance of the eye lids.
• Has the same origin and insertion of the orbital part.

 

The lacrimal part (( the smallest part)):

• Origin: from the post. lacrimal crest and the fascia covering the lacrimal sac.
• Insertion: into the margins of eye lids.
• Nerve supply of orbiculari oculi: temporal and zygomatic branch of facial nerve.
• Action:

1. The orbital part closes the eye forcibly (to avoid danger).
2. The palpebral part closes the eye lightly (as in blinking or during sleep).
3. The lacrimal part dilates the lacrimal sac (helping drainage of tears).
4. The whole muscles contracts reflexly to protect the eye against any danger.

 

Buccinators muscle:

• A quadrilateral muscle occupying the gap between mandible and maxilla forming the most important part of the cheek.

Origin:

1. Alveolar margin of maxilla opposite 3^rd molar tooth.
2. Alveolar margin of mandible opposite 3^rd molar tooth.
3. The pterygomandibular ligament.

 

Insertion:

1. Upper fibers: inserted into the upper lip.
2. Lower fibers: inserted into the lower lip.
3. Middle fibers: decussate at the angle of mouth: the upper members pass to the lower lip while the lower members pass to the upper lip.

 

Nerve supply:

• buccal branch of facial nerve.

 

Actions:

1. Prevent accumulation of food in the vestibule of mouth by keeping the cheeks applied to the gums.
2. When the cheeks are distended with air, buccinators expels it.
3. Used also in whistling.

Superficial relations:

1. It covers by buccophryngeal fascia and buccal pad of fat.
2. Its posterior part overlapped with masseter muscle and pierced by the parotid duct.
3. Its anterior part is covered by facial a. and ant, facial vein.

Orbicularis oris muscle:

• A sphincter m. formed of fibers that surround the oral orifice.

It consists of:

• Extrinsic fibers: derived of other facial muscles (mainly buccinators) which are inserted into the lips.
• Intrinsic fibers: includes incisive slips, mental slips arising from alveolar margin of maxilla and mandible respectively.

Nerve supply:

• buccal branch of facial nerve.

Actions:

1. Closes the mouth by bringing the lips close together.
2. Compresses the lips against the teeth.
3. Important for speech (articulation for the letters p,b,m)
4. Kissing

Arterial supply of the face:

• The face is supplied by two sets of arteries:  anterior and posterior

Anterior sets of arteries: include:

Facial artery:

• The principle artery of the face.
• Origin: it arises from the anterior aspect of external carotid artery in the upper part of the neck.
• course and relations in the face:

1. It enters the face by hooking upwards over the inferior border of mandible at the antero-inf. Angle of masseter m.
2. In the face, it turns in the tortuous course upward and forwards in the ant. facial vein first superfascial to buccinators m. till it rich the point 1 cm behind the angle of mouth. Then it ascends along the side of nose to reach the med. angle of eye.
3. Ends: at the med. angle of the eye by becoming angular a.

Branches in the face:

1. Inferior labial artery à to the lower lip
2. Sup. Labial artery à to the upper lip and it gives a septal branch to nasal septum.
3. Nasal artery à to the nose.

Supratrochelear artery :

• arises in the orbital from ophthalmic a. branch from I.C.A

Supraorbital artery :

• arises from the orbit from ophthalmic a. branch from I.C.A, it anastomoses with temporal artery , free communication between internal and external carotid arteries.

Infra-orbital artery :

• the continuation of maxillary a. (larger terminal branch of carotid a.), reaching the face through infraorbital foramen.

Mental artery :

• branch of inferior Alveolar artery (branch from maxillary a.). reaches face through mental foramen and supplies chin.

Posterior sets of arteries:

Transverse facial artery:

• Branch of superfascial temporal a. inside parotid gland.
• Emerges from the anterior border of parotid gland, Runs across the neck just above parotid duct.

 

Zygomatic-orbital artery:

• Branch of superfascial temporal a. after it emerges from parotid gland and runs transversally across the zygomatic arch towards the orbit.

 

Venous drainage of the face:

• The face is drained by yellowing veins. 

Anterior facial vein:

• Begins at the medial angle of eye by the union of supraorbital and supratrochlear veins.

1. N.B: at its beginning at the medial angle, it's called angular vein. This becomes the facial vein which pursues a straight course behind tortuous facial a.

• It runs downwards and backwards behind the facial artery.
• It leaves the face to enter the neck at the antero-inferior angle of masseter muscle.
• It ends by piercing the investing layer of deep fascia of neck and is joined by anterior division of retromandibular vein to form common facial vein.

Tributaries:

• Supraorbital and Supratrochlear vein.
• Tributaries corresponding to the branches facial artery.
• The deep facial vein: which passes deep to the mandible, connecting the ant. Facial v. with the pterygoid plexus.

Deep venous anastomosis:

• At the medial angle of eye: the anterior facial vein communications with the ophthalmic veins, which drain directly into cavernous venous.

• The deep facial vein connects the ant. facial vein with pterygoid plexus that in turn connects with cavernous sinus through valveless emissary veins that pass through foramen oval and foramen lacerum. 

Retromandibular vein (posterior Facial vein):

• Begins: inside substance of parotid gland by the union of two veins:

1. Maxillary vein (draining the pterygoid plexus of w.)
2. Superficial temporal vein.

• It descends inside the parotid gland (deep to facial n. and its branches)
• Ends: at the lower end of gland by dividing into two divisions (anterior and posterior):

1. The anterior division joins the anterior  Facial vein to form the common facial vein which ends in the I.J.V. (internal jugular vein).
2. The posterior division joins the post. Auricular vein to form the external jugular vein which ends in the subclavian vein.

Dangerous area of the face:

• The area of facial skin bounded by eyes, the nose and the upper lip.
• It is a potentially dangerous zone to have an infection, that may spread via ophthalmic veins or pterygoid plexus to the cavernous venous with resulting in cavernous venous thrombosis that may be fatal unless adequately treated by antibiotics.

Lymphatic Drainage of Scalp:

1. Pre-auricular lymph nodes: These drain anterior part of scalp, except an area below the center of forehead.
2. Post auricular lymph nodes: These drain posterior part of scalp.
3. Occipital lymph nodes: A part of posterior aspect of scalp is drained by these nodes also.

1. Sensory nerve Supply of Scalp:

• Each half of the scalp is supplied by 8 sensory nerves.

In front of the ear:

• These are four in number. All are branches of the trigeminal nerve.

1. Supratrochlear nerve
2. Supraorbital nerve
3. Zygomaticotemporal nerve
4. Auriculotemporal nerve

Behind the ear: 

• These are also four in number and arise from the cervical plexus.

1. Great auricular nerve (C2, 3)
2. Lesser occipital nerve (C2)
3. Greater occipital nerve (C2)
4. Third occipital nerve (C3)

2. Motor Nerve Supply of Scalp:

• Each half of the scalp is supplied by branches of facial nerve.

a. Temporal branch of facial nerve:

• Supplies the frontal belly of occipitofrontalis muscle.

b. Posterior auricular branches of the facial nerve:

• Supplies the occipital belly of occipito-frontalis muscle.