THE VAGINAL MUSCLES
THE OUTER MUSCLES
The outer layer, just beneath the skin, is called the perineum. This layer primarily provides support to the vagina.
The muscles of the perineum form a partial ring around the vaginal opening. The majority of this ring consists of the left and right bulbocavernosus muscles.
The center of this ring is a fusion point where the bulbocavernosus muscles connect with the transverse perineal muscles. This fusion point is called the perineal body.
The outer vaginal muscles are not the muscles involved in Kegel exercises and women are not usually able to tighten them at will. However, when they are intact and firm they generate a snug yet elastic sensation during intercourse.
THE INNER MUSCLES
The inner layer of vaginal muscles responsible for vaginal tightening are called the levator ani muscles or simply the levator muscles.
The levator muscles form the floor of the pelvis and support the bladder, the vagina and the rectum during normal activity.
These muscles consist of one large sheet of muscle tissue that spans across the entire bony pelvis with an opening in the center called the levator hiatus or the genital hiatus.
This sheet of muscle is shaped like a bowl with the levator hiatus at its center.
The periphery of this bowl is attached to its surroundings by a tough layer of leather-like tissue called fascia.
The center is attached to the tailbone and the perineal body.
THE PUBORECTALIS MUSCLE
The central portion of the levator ani muscle group is called the puborectalis muscle (blue). This muscle loops around from front to back and forms a sling that tightens around the vagina, the bladder and the rectum.
When the puborectalis muscle contracts, the gap between the two sides constricts and the vagina tightens.
Vaginal childbirth can damage the puborectalis muscle by either damaging its nerve supply or by loosening its attachments. Once damaged, the muscle is unable to contract properly and the ability to tighten the vagina is lost or impaired.
The puborectalis muscle is the target of vaginal rejuvenation tightening procedures.