The orbicularis oris muscle is a sphincter muscle that is located in the face and surrounds the mouth. It is a broad, thin muscle that is composed of several fibers that are arranged in a circular pattern. The muscle is attached to the skin of the lips and the mucous membrane that lines the inside of the mouth.
Location
The orbicularis oris muscle is located in the lower part of the face, surrounding the mouth. It is bordered by the buccinator muscle on the sides and the risorius muscle on the corners of the mouth.
Structure
The orbicularis oris muscle is made up of two main groups of fibers: the circular and the sphincter fibers. The circular fibers encircle the mouth and are responsible for closing the lips. The sphincter fibers, on the other hand, are located around the oral orifice and are responsible for puckering the lips.
The orbicularis oris muscle has a complex structure and is made up of several layers of muscle fibers. The outer layer is composed of circular fibers that run in a horizontal direction, while the inner layer is made up of sphincter fibers that run in a vertical direction.
The orbicularis oris muscle is innervated by the facial nerve, which is responsible for the muscle’s voluntary movement. The muscle receives blood supply from the facial artery and the superior and inferior labial arteries.
Function
The orbicularis oris muscle plays an important role in facial expression, speech, and swallowing. It is responsible for the movement of the lips and helps in the formation of various facial expressions, such as smiling, pouting, and kissing.
In speech, the orbicularis oris muscle helps in the formation of certain sounds, such as “m,” “b,” and “p.” It also helps in the formation of certain vowel sounds, such as “oo” and “ah.”
During swallowing, the orbicularis oris muscle helps to close the lips and form a seal around the mouth, preventing food from escaping.
Clinical significance
The orbicularis oris muscle can be affected by various disorders and conditions, such as Bell’s palsy and facial paralysis. Bell’s palsy is a condition in which the facial nerve becomes inflamed, resulting in weakness or paralysis of the muscles on one side of the face. Facial paralysis, on the other hand, is a condition in which the facial nerve is damaged, resulting in weakness or paralysis of the muscles on one or both sides of the face.
Both Bell’s palsy and facial paralysis can affect the orbicularis oris muscle, resulting in difficulty in closing the lips and forming facial expressions. Treatment for these conditions may involve medications, physical therapy, and surgery.
