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Pars labialis
Other Terms:
Pars labialis (Musculus orbicularis oris),
Pars labialis musculus orbicularis oris
Muscle parts
Marginal part; Labial part
Latin name
Musculus orbicularis oris
Latin muscle parts
Pars marginalis; Pars labialis
Group
Branchial arch muscle – second arch (Facial muscle)
Etymology
The English name for this muscle is the little circle muscle of the mouth. The word orbicularis comes from the Latin orbis meaning “circle or disk” and ulus which is a diminutive ending meaning “little.” The Latin term oris is from the Latin os meaning “a mouth or opening.”
Origin
Modiolus at the angle of the mouth (both marginal and peripheral parts); maxilla above second incisor; mandible below second incisor.
Insertion
The peripheral part interdigitates with opposite fibers crossing the midline to insert into the skin near the opposite midline from the nasolabial sulcus to the margin of the red lip superiorly and from the mentolabial sulcus to the margin of the red lip inferiorly. The marginal part, likewise, interdigitates and crosses the midline to insert into the red lip dermis just opposite the midline in both superior and inferior lips.
Action
This complex arrangement of muscle fibers performs a variety of actions associated with the lips and adjoining muscles. It functions in modifying the actions of the surrounding muscles that insert into the lips and angles of the mouth. It functions in puckering the lips and assists in compressing the lips together and turning them inward.
Nerve supply
Facial nerve (Cranial nerve VII)
Blood supply
Superior labial and inferior labial branches of the facial artery.
Latin
Pars labialis musculus orbicularis oris
