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Origins, insertions, innervation and functions of the levator ani muscle.
Hey, everyone. It’s Matt from Kenhub. And in this tutorial, we will discuss the origin, insertion, innervation, and function of the levator ani.
The levator ani forms the main part of the pelvic diaphragm, a layer of the pelvic floor known as the cranial layer. The levator ani is made up of three muscles.
The puborectalis muscle originates lateral from the symphysis on both sides and encircles the rectum, which causes a ventral bend between the rectum and anal canal. It is partly interwoven with the external anal sphincter.
The pubococcygeus muscle runs from the pubic bone to the tendinous center of the perineum, anal coccygeal body, and coccyx.
In men, medial muscle fibers are partly connected to the prostate. The iliococcygeus muscle extends more laterally from the fascia of obturator internus muscles to the coccyx.
As a whole, the levator ani builds a V-shaped structure. Both levator arms limit a triangle opening which is divided by prerectal fibers into the urogenital hiatus and anal hiatus.
The urogenital hiatus is the pathway for the urethra, and in women, the vagina. The rectum runs through the anal hiatus.
This muscle group is primarily supplied by direct branches of the sacral plexus. To a small degree, the pudendal nerve contributes to its innervation as well.
Through its tonic activity, the levator ani stabilizes the abdominal and pelvic organs on the one hand and controls the opening and closing of the levator hiatus on the other hand.
While in quiescent state, the urethra and the rectum are mechanically closed at the levator hiatus. The muscle relaxes at the beginning of urination and defecation.
By this means, the levator ani muscle plays a crucial role in the preservation of urinary and bowel continence.