Musculus Sphincter Ani externus, also known as the external anal sphincter, is a muscular structure located in the perineum region of the body. It is responsible for the voluntary control and regulation of the anal opening, allowing for the passage or retention of stool and gas.
The external anal sphincter is composed of striated muscle fibers, which are under conscious control. It forms a circular band around the anal canal, encircling the anal orifice. When contracted, the sphincter closes off the opening, preventing involuntary release of feces or gas. This mechanism allows for the voluntary regulation of defecation.
The muscle receives its neural innervation from the pudendal nerve, specifically the inferior rectal branch. This nerve supplies the necessary signals for the contraction and relaxation of the external anal sphincter.
In terms of function, the external anal sphincter plays a crucial role in maintaining continence. It assists in the voluntary retention of feces until an appropriate time for defecation. It also aids in controlling the release of gas and preventing involuntary leakage.
Disorders or dysfunction of the external anal sphincter can lead to changes in bowel control, such as fecal incontinence or difficulty with bowel movements. These conditions may require medical intervention or specific exercises to strengthen the muscle and restore normal function.
Overall, the musculus sphincter ani externus is an important anatomical structure involved in the voluntary control of defecation and maintenance of continence in the human body.
