Download Lip Anatomy

Anatomy of the lip
Embryology

two medial nasal swellings and the maxillary swellings fuse to form the upper lip.

Philtrum derived from the intermaxillary segment of the medial nasal processes

Lower lip derived from paired mandibular swelling
Surface landmarks

The intercommissural distance is between 4 and 5 cm when the lips are closed and
relaxed.
Muscles

Oral competence
o controlled by the orbicularis oris muscle

unreplaced loss of a significant part of the orbicularis precludes
continence

muscles of facial expression modulate orbicularis position, but may
be transected without affecting the sphincteric action of the
orbicularis.

Deep and oblique fibers approximate the lips to the alveolar arch

Superficial fibers (composed mainly of decussating fibers of
buccinators), purse and protrude the lips)

Lip Elevators
o Principle elevator is levator labii superioris
o Zygomaticus major and levator anguli oris musles help draw the lateral lip
up and back

Lateral movers
o Risorius and buccinator mm clear the gingival sulci.

Depressors
o Mainly controlled by the platysma, depressor labii inferioris and depressor
anguli oris muscles
o Lip eversion - mentalis
Arteries

Blood supply to both lips is derived from the facial arteries.

On each side, the superior and inferior labial branches arise from the facial arteries
to travel tangentially deep to the orbicularis oris muscles.

Lower lip may also be supplied by sublabial and submental arteries

Superior labial artery
o Larger and more tortuous than inferior
o 50% runs between orbicularis and mucosa
o 50% runs in orbicularis
o 45mm length
o Alar branch 2.6cm from origin, septal branch 3.3cm from origin
o Branches from the facial artery 1cm lateral and 1cm superior to
commissure (rotation point for Gillies, McGregor flap)
o Located 7mm from inferior border of red lip, 8mm from anterior border
and 3mm from posterior border
o 25-36% of labial arteries have a unilateral origin

Inferior labial artery
o Branches from the facial artery 2.6cm lateral and 1.5cm inferior to
commissure
o Position of ILA is on the inner aspect of the lip just above the lower
margin of the vermillion
o Located 6mm from superior border, 6.5mm from anterior border and 5mm
from posterior

Thus a 1cm thick flap will capture the labial vessel
Lymphatics

The upper lip
o lymphatics are unilateral except in the midline
o
coalesce to form 5 primary trunks – mainly to ipsilateral submandibular
chain
o Some drainage to periparotid nodes

Lower lip
o Form 5 trunks
o central segment drains to the submental nodes with frequent crossover.
o the lateral two thirds drains mainly into the submandibular glands and
contralateral drainage is uncommon
Nerves
Motor
 Motor nerves arise from the buccal and marginal mandibular branches of cranial
nerve VII.

The elevators are innervated by buccal branches. The depressors are innervated by
the marginal mandibular branches.

SRPS – buccinators is supplied only by the buccal branch but last – Buccal and
MM
Sensory

Sensory innervation to the lips is provided by the terminal branches of the inferior
alveolar nerve (V3) and the infraorbital nerve (V2).

The mental nerve and the mental foramen are important routes of spread in lower
lip carcinomas and spread along the perineural lymphatic and then via the mental
foramen into the inf alveolar canal along the mandibular nerve and then to the
skull base
Aesthetics

Skin of the lips joins the red portion or vermillion in a transitional zone the
mucocutaneous ridge which is an important land mark

Mouth width is 1.5x the width of the nose

In the “normal” lip position, the commissures lie between the pupils

In most the vermillion of the upper lip is thinner and slightly more recessed than
the pout like eversion of the lower lip

Transverse length is slightly greater for the upper lip (8cm ) than the lower lip(7.5
cm)

The lower lip has no definitive central structure, like the philtral columns of the
upper lip, and therefore it may sustain greater loss without distortion than the
upper lip. This permits the lower lip to donate larger amounts of tissue for upper
lip reconstruction.