Human Anatomy Part 1 - K. A. Dyubenko, A. K. Kolomiyytsev, Yu. B. Chaykovsky 2002

Special Part
Myology, myologia [the study of muscles] - Muscles and Fascia of the Head
Muscles of facial expression, musculi faciei - Muscles bounding the oral fissure

1. The circular Muscle of the Mouth, m. orbicularis oris, resembles a broad annular band located within the thickness of the Lips. The muscle bundles firmly fuse with the Skin and run from the angle of the mouth into the upper and lower lips, intertwining with the fibers of the opposite side, and terminate in the skin near the midline. The muscle is divided into a marginal part, pars marginalis, and a labial part, pars labialis.

Function: closes the oral fissure and projects the lips forward.

Blood supply: aa. labialis superior et inferior, a. mentalis.

2. The zygomaticus Major and minor Muscles, mm. zygomatici major et minor, originate from the lateral surface of the Zygomatic bone. Some of the muscle bundles are a continuation of m. orbicularis oculi. The muscles run downward and medially, weaving into the orbicularis oris muscle and the skin at the angle of the mouth.

Function: pull the angle of the mouth upward and outward, and elevate the nasolabial fold.

Blood supply: aa. infraorbitalis, buccalis.

Innervation: n. facialis.

3. The levator labii superioris alaeque nasi muscle, m. levator labii superioris alaeque nasi, originates from the infraorbital margin, above the infraorbital foramen of the Maxilla. A muscle bundle separates from it and runs toward the nasal wing, m. levator labii superioris alaeque nasi. These muscles run downward to form a quadrilateral muscular plate, the bundles of which weave into the skin of the upper lip, the m. orbicularis oris, and the skin of the nasal wing.

Function: elevates the upper lip and draws the nasal wing upward.

Blood supply: aa. infraorbitalis, labialis superior.

Innervation: n. facialis.

4. The levator anguli oris muscle, m. levator anguli oris, originates below the infraorbital foramen from the canine fossa, runs downward, and weaves into the skin at the angle of the mouth and the m. orbicularis oris.

Function: elevates the angle of the mouth and the upper lip in the incisor region.

Blood supply: aa. infraorbitalis, buccalis.

Innervation: n. facialis.

5. The buccinator muscle, m. buccinator, originates from the oblique line on the ramus of the Mandible and the outer surface of the maxilla in the area of the molar alveoli. Running forward, the muscle bundles weave into the m. orbicularis oris, as well as into the mucous membrane and skin of the angle of the mouth, and the upper and lower lips. The buccal fat pad, corpus adiposum buccae, lies adjacent to the outer surface of the m. buccinator.

Function: draws the angle of the mouth laterally, and upon bilateral contraction, widens the oral fissure and presses the inner surface of the Cheeks against the anterior Teeth.

Blood supply: a. buccalis.

Innervation: n. facialis.

6. The risorius muscle, m. risorius, is inconstant; some of its bundles originate from the parotid fascia and the skin of the nasolabial fold region. Running medially, the muscle bundles weave into the skin at the angle of the mouth.

Function: retracts the angle of the mouth laterally.

Blood supply: aa. facialis, transversa faciei, buccalis.

Innervation: n. facialis.

7. The depressor anguli oris muscle, m. depressor anguli oris, originates from the anterior surface of the mandible, below the mental foramen. The muscle courses upward, narrows, and reaches the angle of the mouth, where a part of its bundles weaves into the skin of the angle of the mouth, while another part enters the thickness of the upper lip and the m. levator anguli oris.

Function: depresses the angle of the mouth, smooths the nasolabial fold, and imparts a sad expression to the face.

Blood supply: aa. labialis inferior, mentalis, submentalis.

Innervation: n. facialis.

8. Depressor labii inferioris muscle, m. depressor labii inferioris — originates from the anterior surface of the mandible, extends superiorly, and blends into the skin of the lower lip and chin. The medial bundles of the muscle and the lower lip decussate with the bundles from the opposite side.

Function: depresses the lower lip.

Blood supply: aa. labialis inferior, mentalis, submentalis.

Innervation: n. facialis.

9. Mentalis muscle, m. mentalis — originates adjacent to the previous muscle from the alveolar eminence of the mandibular incisors, extends inferiorly, and inserts into the skin of the chin.

Function: elevates the skin of the chin, everts the lower lip.

Blood supply: aa. labialis inferior, mentalis.

Innervation: n. facialis.

Thus, all facial (mimetic) muscles are innervated by the branches of n. facialis (VII).