Anatomy and Function of the Female Pelvic Floor

Muscular Supports of the Pelvic Floor

The pelvic viscera, (bladder, rectum, pelvic genital organs and terminal part of the urethra) reside within the pelvic cavity (or the true pelvis). This cavity is located within the lesser part of the pelvis, beneath the pelvic brim.

The levator ani and coccygeus muscles that are attached to the inner surface of the minor pelvis form the muscular floor of the pelvis. With their corresponding muscles from the opposite side, they form the pelvic diaphragm.

The levator ani is a broad sheet of muscle. It is composed of three separate paired muscles, called the pubococcygeus, puborectalis and iliococcygeus. These muscles have attachments to the pelvis as follows:

  • Anterior – The pubic bodies of the hip bone.
  • Laterally – Thickened fascia of the obturator internus muscle, known as the tendinous arch.
  • Posteriorly – The ischial spines of the hip bone.

The levator ani muscle consists of three parts: the pubococcygeus, the puborectalis, and the iliococcygeus muscles. The pubococcygeus and the puborectalis muscles form a U-shape as they originate from the pubic bone on either side of the midline and pass behind the rectum to form a sling. This sling of muscle is composed of muscle fibers and therefore is suited to maintaining constant tone.

A number of muscles help make up the walls of the cavity; the lateral walls include the obturator internus and the pirformis muscle, with the latter also forming the posterior wall.

The pelvic floor muscles are innervated by branches of the pudendal nerve, roots S2, S3 and S4.

The pelvic floor is a funnel-shaped musculature structure. It attaches to the walls of the lesser pelvis, separating the pelvic cavity from the inferior perineum (region which includes the genitalia and anus).

In order to allow for urination and defecation, there are a few gaps in the pelvic floor. There are two ‘holes’ that have significance:

  • The urogenital hiatus – An anteriorly situated gap, which allows passage of the urethra (and the vagina in females).
  • The rectal hiatus – A centrally positioned gap, which allows passage of the anal canal.
  • Between the urogenital hiatus and the anal canal lies a fibrous node known as the perineal body which joins the pelvic floor to the perineum.

Function of the Pelvic Floor Muscles

As the floor of the pelvic cavity, the muscles have important roles to play in the correct functions of the pelvic and abdominal viscera. The roles of the pelvic floor muscles are:

  • Support of abdominopelvic viscera (bladder, intestines, uterus etc.) through their tonic contraction.
  • Urinary and fecal continence. The muscle fibers have a sphincter action on the rectum and urethra. They relax to allow urination and defecation.
  • The pelvic diaphragm has a crucial role in sexual response and pelvic floor functioning is tightly linked to a healthy female sexual cycle
  • The muscles of the pelvic floor work with the abdominal and back muscles to stabilise and support the spine.