The zygomaticus minor muscle is a

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

of facial expression. It originates from the

zygomatic bone In the human skull, the zygomatic bone (from grc, ζῠγόν, zugón, yoke), also called cheekbone or malar bone, is a paired irregular bone which articulates with the maxilla, the temporal bone, the sphenoid bone and the frontal bone. It is si ...

, lateral to the rest of the

levator labii superioris muscle The levator labii superioris (pl. ''levatores labii superioris'', also called quadratus labii superioris, pl. ''quadrati labii superioris'') is a muscle of the human body used in facial expression. It is a broad sheet, the origin of which exten ...

, and inserts into the outer part of the upper lip. It draws the

upper lip The lips are the visible body part at the mouth of many animals, including humans. Lips are soft, movable, and serve as the opening for food intake and in the articulation of sound and speech. Human lips are a tactile sensory organ, and can be ...

backward, upward, and outward and is used in smiling. It is innervated by the

facial nerve The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of tas ...

(VII).

Structure

The zygomaticus minor muscle originates from the

. It inserts into the tissue around the upper lip, particularly blending its fibres with

orbicularis oris muscle In human anatomy, the orbicularis oris muscle is a complex of muscles in the lips that encircles the mouth. It is a sphincter, or circular muscle, but it is actually composed of four independent quadrants that interlace and give only an appearance ...

. It lies lateral to the rest of

, and medial to its stronger synergist

zygomaticus major muscle The zygomaticus major muscle is a muscle of the human body. It extends from each zygomatic arch (cheekbone) to the corners of the mouth. It is a muscle of facial expression which draws the angle of the mouth superiorly and posteriorly to allow one ...

. It travels at an angle of approximately 30°. It has a mean width of around 0.5 cm.

Nerve supply

The zygomaticus minor muscle is supplied by the

buccal branch The buccal branches of the facial nerve (infraorbital branches), are of larger size than the rest of the branches, pass horizontally forward to be distributed below the orbit and around the mouth. Branches The ''superficial branches'' run beneath ...

of the

(VII).

Variation

The zygomaticus minor muscle may have either a straight or a curved course along its length. It may attach to both the

and the lateral alar region. It may be underdeveloped in some people, with its role taken over by nearby synergists. These synergists rarely change shape or position, but any difference in smile is usually imperceptible.

Function

The zygomaticus minor muscle draws the

up, back, and out, such as during

smiling A smile is a facial expression formed primarily by flexing the muscles at the sides of the mouth. Some smiles include a contraction of the muscles at the corner of the eyes, an action known as a Duchenne smile. Among humans, a smile expresses ...

History

The zygomaticus minor muscle is sometimes referred to as the "zygomatic head" of the

levator labii superioris The levator labii superioris (pl. ''levatores labii superioris'', also called quadratus labii superioris, pl. ''quadrati labii superioris'') is a muscle of the human body used in facial expression. It is a broad sheet, the origin of which extend ...

muscle.

Images

File:Zygomaticus minor muscle animation small.gif, Zygomaticus minor muscle (shown in red).

References

External links

PTCentral
{{Authority control Muscles of the head and neck