Quadratus labii

Quadratus labii is a group of facial muscles that are primarily responsible for the movements of the lips. The group is composed of three muscles: the quadratus labii superioris, the quadratus labii inferioris, and the quadratus labii lateralis. These muscles are part of the larger facial musculature system and play a crucial role in facial expressions and speech.

Anatomy

The quadratus labii muscles originate from the zygomatic bone and the maxilla, and insert into the skin and muscle of the upper and lower lips. The superioris and inferioris are responsible for elevating and depressing the upper and lower lips respectively, while the lateralis pulls the corners of the mouth laterally.

Function

The primary function of the quadratus labii muscles is to control the movements of the lips. This is essential for a variety of facial expressions, as well as for the articulation of certain speech sounds. In addition, these muscles also play a role in eating and drinking by helping to close the mouth and keep food and liquid inside.

Clinical significance

Damage or dysfunction of the quadratus labii muscles can lead to a variety of clinical conditions. For example, Bell's palsy is a condition that can cause weakness or paralysis of the facial muscles, including the quadratus labii. This can result in difficulties with speech, eating, and making facial expressions. Treatment typically involves physical therapy to help restore muscle function.

See also

• Facial muscles
• Facial nerve
• Bell's palsy

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