The Zygomaticus Minor Muscle is a slender facial muscle involved in facial expressions. It originates from the zygomatic bone and attaches to the lateral portion of the upper lip, affecting movements such as smiling. It is innervated by the facial nerve (cranial nerve VII).

Anatomy

Morphology and Connection Points

The Zygomaticus Minor Muscle courses at an inferomedial angle of approximately 30° and has an average width of 0.5 cm. The muscle originates from the lateral surface of the zygomatic bone and inserts into the muscle tissue of the upper lip. Its origin is located just posterior to the zygomaticomaxillary suture and joins the levator labii superioris muscle at its distal end. In terms of its relationship, the muscle is positioned lateral to the levator labii superioris and medial to the zygomaticus major muscle. The course of the muscle fibers can vary between individuals; they can be straight or curved, and sometimes, in addition to the upper lip, they can also insert into the lateral alar region.

Embryological Origin and Classification

The Zygomaticus Minor Muscle originates embryologically from the second pharyngeal arch and is classified among the muscles responsible for facial expressions. Its motor innervation is provided by the facial nerve (cranial nerve VII). Functionally, it is included in the facial muscle group and plays a key role in facial expressions, especially smiling movements. In some cases, when the muscle is underdeveloped, its function can be compensated for by adjacent muscles.

Nerve Innervation and Vascular Supply

Motor innervation of the Zygomaticus Minor Muscle is provided by the zygomatic and buccal branches of the facial nerve (CN VII). These nerves control the precise and coordinated movements of the muscle. While detailed information on its vascular supply is not included in the text, it is known that facial muscles are generally supplied by branches of the facial artery. Neural and vascular structures are critical for the proper execution of the muscle's facial functions.

Function and Clinical Relationships

The Zygomaticus Minor Muscle plays a particularly active role during smiling. It pulls the upper lip upward, backward, and outward, ensuring a positive facial expression suitable for social communication. This movement is a key component of facial expression coordination and is effective in conveying emotional expressions. While specific clinical information is not included in the text, underdevelopment or dysfunction of the zygomaticus minor muscle can lead to asymmetry in facial expressions or smile disorders. Muscle variations and their adjacent relationships should be considered in surgical interventions, particularly in facial aesthetics and reconstruction procedures. Individual differences in muscle fiber course and insertion points are important for surgical planning and preventing nerve damage.