The pelvic floor (or pelvic diaphragm) is composed mainly of muscles that form the inferior lining of the pelvic cavity. It is a funnel-shaped muscular structure that attaches to the walls of the lesser (true) pelvis, separating the pelvic cavity from the perineum inferiorly.
There are a few gaps in the pelvic diaphragm, including:
- Urogenital hiatus - located anteriorly, allows passage of the urethra and the vagina in females;
- Rectal hiatus (also called the anal hiatus) - situated centrally, posterior to the urogenital hiatus; allows passage of the anal canal.
The pelvic floor is connected to the perineum via the perineal body - a fibromuscular structure lying in the subcutaneous tissue between the previously mentioned gaps, to be more precise - between the anus and posterior aspect of the vaginal orifice in females.
The perineal body is located in the center of the perineum and is also the site where attach and converge mostly the perineal muscles. Therefore, it is also known as the central tendon of the perineum.
The main functions of the pelvic floor muscles are described below.
- During childbirth, pelvic floor muscles provide support and passive movements of the fetus, pushing it through the birth canal that is located in the pelvis. At the same time, these muscles also relax and allow the fetus to exit the pelvis.
- Tonic contractions of the pelvic floor muscles provide support for the abdominopelvic organs (bladder, intestines, uterus, etc.).
- During activities such as lifting heavy objects or coughing, these muscles create resistance to increasing of the intra-pelvic or intra-abdominal pressure.
- The pelvic diaphragm also plays an important role in ensuring urinary and fecal continence by acting as a sphincter on the rectum and the urethra. As these muscles relax, they allow defecation and urination.
- In females, during sexual intercourse, the pelvic floor muscles maintain clitoral erection, as well as providing the tone of the vaginal wall.