Face and Scalp

Development of the Face – begins at 4 weeks

facial primordia are arranged around the stomodeum (future mouth)

frontalnasal prominance: surrounds the ventrolateral part of the forebrain
paired maxillary prominences: derived from 1^st arch
paired mandibular prominences: derived from 1^st arch

the mandibular prominences fuse first to form the mandible

paired nasal placodes appear on the inferolateral aspect of the frontal nasal prominences; proliferating mesenchyme gives rise to medial and lateral nasal prominences in a horse-shoe shape around a nasal pit (future anterior nares)

the medial nasal prominences fuse to form the nasal septum, the philtrum, and the primary palate

as the maxillary prominences grow towards the midline, the nasal prominences grow inferiorly and medially; the maxillary and lateral nasal prominences meet at the nasolarcrimal groove (which later degenerates)

the lateral nasal prominences grow faster than the medial and eventually grow over the nasal pit to form the nasal sac which becomes the nasal cavity

paranasal sinuses develop from the pneumatization of the maxilla, frontal, ethmoid, and sphenoid bones during childhood and adolescence

summary:

frontal nasal prominances. Þ forehead, dorsum and apex of nose

lateral nasal prominance Þ sides of nose

medial nasal prominance Þ septum, philtrum

maxillary prominance Þ upper cheek and lip

mandibular prominance Þ mandible, chin, etc

Development of the Palate – weeks 5-12; weeks 6-9 are the most important

primary palate – the internal aspect of the medial nasal prominences gives rise to the median palatine process anteriorly

secondary palate – internal aspects of the maxillary prominences give rise to the lateral palatine prominences

these two prominences grow towards each other and fuse in the 12^th week; the median process gives rise to the anterior aspect of the hard palate; the lateral prominences give rise to most of the hard and soft palates

cleft lip and palate can occur on any of the lines of fusion during the formation of the face and of the palate; may be uni- or bi- lateral (1/2500 live births)

Development of the Eye and Ear

neuroectoderm diverticula of the diencephalon give rise to the optic cups which pinch off parts of the ectoderm (lens placodes, from the optic placodes); lens placodes Þ lens, optic cups Þ retina

the hyaloid artery is a branch of the opthalmic a which runs inside the stalk of the optic cup to supply the lens placode; the branch to the lens degenerates, but the rest remains as the central a of the retina

summary:

neuroectoderm Þ retina, optic nerve, muscles of iris, epithelium of iris and cilliary body

surface ectoderm Þ lens, conjunctiva, cornea

mesoderm Þ CT of cornea, iris, sclera, choroid, all eye muscles (except of the iris)

Development of the Outer Ear

external acoustic meatus is a derivative of the first branchial arch

the 1^st and 2^nd arches produce six auricular hillocks on each side of the head; the 2^nd arch outgrows the first and the hillocks give rise to the outer ear

Other Details

Anatomy

SCALP: Skin; Connective tissue; Aponeurosis (galea); Loose connective tissue; periosteum
masseter muscle is the only muscle of mastication which contributes to the contour of the face

Sensory Innervation of Tongue

CN V provides general sensory to the anterior 2/3 of the tongue

CN VII provides taste sensation from the anterior 2/3 of the tongue

Veins of Face and Neck – highly varied (may have multiple external or anterior jugulars, etc)

name vessels by where they are (i.e. anything on the lateral side of the neck is external jugular)

Lymph Drainage of Tongue

tip of the tongue drains to superficial submandibular lymph nodes
back of tongue drains to lymph nodes along the jugular

Parasympathetic Innervation of Head and Neck – from CN III, VII, IX, X

CN IX gives parasympathetic innervation to the parotid glands

Arteries

transverse facial – arises from superficial temporal a, passes under parotid gland, and runs anteriorly along masseter m

anastomoses with branches of the facial

facial –main artery of face; arises from external carotid, hooks around the inferior border of the mandible; winding course

sends off branches that supply most of the face

inferior labial: branch of the facial that supplies the lower lip area

Veins

facial – major venous drainage of the face; begins as union of supraorbital and supratrochlear veins

runs along with the facial artery, but is more superficial and straighter

Nerves

facial nerve (C.N. VII) – supplies muscles of facial expression, platysma, auricular mm, scalp mm

5 branches that emerge from behind the parotid gland and spread over the face like abducted fingers of a hand

provides sensory (taste) to the anterior 2/3 of the tongue

mnemonic: Twin Zebras Bit My Cock Þ temporal; zygomatic; buccal; mandibular; cervical

trigeminal nerve (C.N. V) – largest cranial n; main general sensory innervation of head; motor nerve to muscles of mastication; has three branches; see distribution of dermatomes at left

opthalmic (V¹) – smallest branch, most superior; sensory to skin of upper eyelid, forehead, nose

maxillary (V²) – intermediate division; skin to lateral nose, upper lip, anterior temple area

infraorbital: branch of maxillary; passes through infraorbital foramen; sensory to skin of lateral nose, upper lip, and lower eyelid

mandibular (V³) – inferior division; sensory to skin of mandibular region; also motor to muscles of mastication

buccal – small branch of V³ supplies skin over the buccinator

mental – branch of V³: passes through mental foramen as a branch of the inferior alveolar nerve and supplies skin and mucus membrane of lower lip and gingiva

lingual – general sensory to anterior 2/3 of tongue

Bones

frontal

glabella – smooth, rounded area of frontal bone between the eyebrows; usually hairless (except in cases of unibrow)

superciliary arch – prominance of frontal bone superior to supraorbital margin; more prominent in males; overlies the frontal sinus

maxilla

zygomatic

mandible – largest and strongest facial bone

body – horizontal part of the mandible which holds the teeth

ramus – the vertical part of the mandible

angle – posterior border at which the body and ramus meet

neck – posterior process of the ramus that ends in the head of the mandible

condyle (head) – posterior process of the ramus

coronoid process – anterior process of the ramus

mental foramen – on anterolateral part of body; transmits mental vessels and nerve

lacrimal – small bone on medial border of orbital fossa

fossa: on anterior border; contains lacrimal sac
nasolacrimal canal

occipital

temporal – contains external auditory meatus:

Bony Region

anterior nasal aperture (piriform) – pear-shaped aperature formed by nasal bones and maxilla

nasion – depression at the root of the nose; superior junction of the nasal bones with the frontal bone

teeth – teeth

alveolar processes – on the mandible and maxilla; house the sockets for the teeth

zygomatic arch – processes from the zygomatic and temporal bones come together in the arch

coronal suture, sagittal suture, bregma, lambdoid suture, lambda: covered previously

Joints

temporomandibular (TMJ) – modified synovial hinge joint between condyle of mandible, articular tubercle, and mandibular fossa of the temporal bone; articular capsule is somewhat loose, and dislocations are usually anteriorly; actions of the joint are anterior sliding, and hingelike rotation

Muscles

Muscles of Facial Expression – all innervated by the facial nerve (VII); most originate in fascia or bone, insert on skin

frontalis – muscle of the forehead

action: elevates the eyebrows; wrinkles the forehead

buccinator – attaches lat. to alveolar processes of maxilla and mandible, inserts among the fibers of the obicularis oris muscle

action: aids mastication by pressing the cheeks against the molars

depressor anguli oris – depresses the corners of the mouth

zygomaticus major – origin at zygomatic bone; inserts at corner of mouth

action: elevates corner of mouth i.e. when smiling

levator labii superioris – runs from infraorbital margin to the upper lip

action: everts upper lip

orbicularis oris – sphincter of the mouth

action: alters the shape of the lips, compresses them against the teeth, purses them when whistling, etc

Other Muscles

platysma

origin: fascia over the pectoralis major and deltoid

insertion: inferior border of mandible in skin of face

innervation: cervical branch of facial

action: tenses skin of neck; relieves pressure on veins

masseter

origin: zyogomatic arch

insertion: ramus and coronoid process of mandible

innervation: mandibular nerve (branch of trigeminal)

action: elevates and protrudes mandible; closes jaw

Miscellaneous Structures

parotid gland – largest of the salivary glands; located inferior to the ear

parotid duct – emerges from anterior end of duct and passes anteriorly over the masseter, turns at the anterior border of the masseter and plunges into the buccinator muscle

papilla – where the duct opens; opposite the second maxillary molar

buccal fat pad – lies in cheek between the buccinator and the superficial facial mm

labial glands – multiple acinous glands between the mucosa of the lips and the opening on the inner lip

lateral nasal cartilage – lateral portions of nose between alar cartilage and nasal bones

septal nasal cartilage – runs in the center of the nose, separates nasal cavities

alar nasal cartilage – left and right halves, forms the tip and underside of the nose

auricle – the external ear

helix – superior portion of auricle; rim of the ear

antihelix – lies just inside the helix on the posterolateral portion of the ear

tragus – at anterior border, projects laterally

lobule – inferior portion of the auricle