Pelvic Floor Anatomy

This information was brought to you with the help of The Continence Foundation of Australia and Dr. Hannah Strom of Awake Pelvic Health and Wellness.

What Are Pelvic Floor Muscles?

The pelvic floor muscles play a crucial role in controlling the release of urine, feces, and gas, as well as in delaying emptying until it is convenient. When you engage the pelvic floor muscles, they elevate the internal organs within the pelvis and tighten the openings of the vagina, anus, and urethra. Relaxing these muscles allows for the passage of urine and feces. This function becomes particularly significant if the muscles surrounding the urethra or anus are not functioning properly, which can occur after childbirth.

In addition to their role in urinary and bowel control, the pelvic floor muscles are essential for sexual function. Voluntary contractions or squeezing of the pelvic floor muscles enhance sexual sensation and arousal. Furthermore, during pregnancy, the pelvic floor muscles provide support for the baby and must be able to relax effectively during the birthing process.

Pelvic Floor Anatomy

The pelvic floor muscles are a vital component of the core muscle groups that help support the spine and regulate intra-abdominal pressure. The deep abdominal muscles, back muscles, and the diaphragm, also play a crucial role in this function.

Comprising multiple layers of muscle and other tissues, the pelvic floor forms a hammock-like structure extending from the front (pubic bone) to the back (coccyx or tailbone), and from one sitting bone (ischial tuberosity) to the other (side to side). The pelvic floor muscles should ideally possess firmness and strength.

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The Five Layers of The Pelvic Floor

Layer 1: The Urogenital Diaphragm

The outermost layer of the pelvic floor is called the urogenital diaphragm. It consists of five specific muscles:

  • External anal sphincter: Controls bowel movements by voluntarily relaxing and contracting the rectum.
  • Compressor urethra: One of the three external urethral sphincters. When contracted, it pulls the urethra backward to stop urine flow.
  • Ischiocavernosus muscle: Helps maintain clitoral erection and contracts the vagina during orgasms.
  • Bulbospongiosus muscle: Assists in clitoral erection and strengthens the opening of the vagina.
  • Superficial transverse perineal muscle: Stabilizes the perineum and supports the vagina.

These muscles are closer to the outside of the body and are not the main muscles responsible for protecting against prolapse or supporting the bladder and vagina.

Layer 2: Deep Transverse Perineal Muscle Layer

The second layer of the pelvic floor consists of two muscles:

  • Deep transverse perineal muscle: Runs horizontally from the pelvic bone to the perineum, helping to support the pelvic floor and expel the last drops of urine.
  • Urethrovaginal sphincter: Wraps around the urethra and vagina, contracting both during muscle contraction.
  • These muscles are also not the ones to focus on during kegel exercises.
Layer 3: Pelvic Diaphragm

The pelvic diaphragm is the third layer, located deeper within the pelvic floor. It consists of five muscles that make up the levator ani:

  • Pubococcygeus muscle: The main muscle supporting the urethra, vagina, and rectum, and responsible for rhythmic contractions during orgasm.
  • Pubovaginalis muscle: Forms a sling to support the vagina and uterus.
  • Puborectalis muscle: Assists in voluntary control of bowel movements by supporting and constricting the anal canal.
  • Iliococcygeus muscle: Surrounds other muscles and assists in pulling the vagina and rectum toward the pubic bone.
  • Ischiococcygeus muscle: Pulls the tailbone forward, stabilizes the sacroiliac joint, and provides tension to the pelvic floor.

The pubococcygeus muscle is particularly important for pelvic floor health and should be the focus of kegel exercises.

Layer 4: Smooth Muscle Diaphragm

The smooth muscle diaphragm consists of two muscles:

  • Internal urethral sphincter: Keeps urine in the bladder until it's time to urinate.
  • External urethral sphincter: Wraps around the urethra and helps control urine flow.
  • The internal urethral sphincter is not under voluntary control, so it's essential to strengthen the voluntary muscles of the pelvic floor.
Layer 5: Endopelvic Fascial Diaphragm

The deepest layer is the endopelvic fascial diaphragm, a system of connective tissue covering the levator ani muscles and supporting the bladder, urethra, uterus, and ovaries. Excessive stretching or tears in this fascia can lead to a loss of support and prolapse of the pelvic organs.

Each of the 14 muscles in the pelvic floor plays a vital role in its overall health. By exercising and strengthening these muscles, improvements can be seen in urinary incontinence and sexual well-being, similar to how other muscles in our body respond to exercise.