The main body of the lips is formed by
muscle and connective tissue. Externally, the lips are covered with skin
and internally with mucous membrane - non-keratinised, stratified, squamous
epithelium. The vermilion border indicates the abrupt beginning of the
transitional zone of the lip. The skin of the transitional zone is hairless
and so thin that it appears red due to the underlying capillary bed. The
upper lip lies between the nose and the oral cavity. In the middle of the
upper lip, the vermilion border forms the Cupid's bow and between the columella
of the nose and Cupid's bow there is a vertical furrow called the philtrum.
The superior and inferior labial arteries, branches of the facial arteries,
anastomose with each other in the lips to form an arterial ring. The upper
lip is supplied by the superior labial branches of the facial and infraorbital
arteries. The lower lip is supplied by the inferior labial branches of
the facial and mental arteries. The upper lip is supplied by the superior
labial branches of the infraorbital nerves (of CNV2) and the
lower lip by the inferior branches of the mental nerves (of CNV3). |
Figure 4. Surface anatomy of the lip |
