The Anatomy Of The 14 Pelvic Floor Muscles

9 min read

Pelvic floor health, sex, and urinary incontinence can be awkward subjects to talk about. Without open communication, these subjects become taboo, making it easier for myths and disinformation to be passed along. One of the best ways to empower ourselves to have better pelvic floor health is to have a thorough understanding of what the pelvic floor is and its many functions. 

What Is The Pelvic Floor? 

We often talk about the pelvic floor as if it is simply a giant hammock of one muscle that supports our bladder, vagina, and other internal organs but it may surprise you to learn that the pelvic floor is actually made up of 14 different muscles, as well as fasciae, organized in 5 distinct layers. The muscles and fasciae each have a unique function related to pelvic floor health. 

Fascia

Fascia is the connective tissue surrounding muscles and organs and helps to stabilize them. Another crucial role that fasciae play in pelvic floor health is by acting as a strong yet flexible casing for the sensitive nerves and blood vessels that pass through and between all of the muscles in the pelvic floor.

The casing of fascia surrounding the blood vessels, nerves, and muscles works to reduce the internal friction of the muscles. 

While the strength and elasticity of the fasciae do not impact the strength and flexibility of the muscles they protect, it is important to know that the strength of the muscles directly impacts the fasciae. A fascia can only be as strong as the muscle it is attached to. 

The good news is that almost all of the muscles that make up the pelvic floor are skeletal muscles which means they can be controlled voluntarily with practice. Performing pelvic floor exercises properly and consistently will result in stronger muscles in your pelvic floor. 

The Five Layers Of The Pelvic Floor 

Layer 1: The Urogenital Diaphragm 

The urogenital diaphragm is the outermost layer of the pelvic floor and contains 5 distinct muscles:

  • External anal sphincter 
  • Compressor urethra 
  • Ischiocavernosus muscle 
  • Bulbospongiosus muscle 
  • Superficial transverse perineal muscle 

The external anal sphincter voluntarily relaxes and contracts the rectum to control bowel movements and the compressor urethra is one of the 3 external urethral sphincters. The two ends of the compressor urethra are attached to the left and right sides of the pelvic bone and form an arch over the urethra. 

When you contract the compressor urethra, the urethra is pulled backward toward the vagina to stop the flow of urine. 

External urethral sphincter, Urethrovaginal sphincter, compressor urethra

Urogenital Triangle 

The remaining three muscles of the urogenital diaphragm form what is known as the urogenital triangle. Imagine the upper point of the triangle located at the clitoris and the base of the triangle located at the perineum, the space between the vagina and anus.

The ischiocavernosus muscle acts as the two sides of the triangle, the superficial transverse perineal muscle acts as the base of the triangle, and the bulbospongiosus muscles are like a pair of two parentheses inside the triangle which sit between the perineum and the clitoris. 

The ischiocavernosus muscle helps to maintain clitoral erection contracts the vagina during orgasms. Clitoral erection is the swelling of the clitoris during sexual arousal.

The bulbospongiosus muscle in the center of the triangle also assists in clitoral erection and it strengthens the opening of the vagina. The superficial transverse perineal muscle stabilizes the perineum and supports the vagina. 

It is very common for women to mistakenly use the urogenital muscles when doing kegel exercises. Even though contracting the compressor urethra and the muscles of the urogenital triangle will stop the flow of urine, contracting these muscles is NOT how a proper Kegel exercise is performed.

These muscles are closer to the outside of the body than any other pelvic floor muscles but it is the deeper muscles of the pelvic floor that do the bulk of the work in protecting against prolapse and supporting the bladder and vagina. 

Layer 2: Deep Transverse Perineal Muscle Layer 

The second layer of the pelvic floor has just two muscles: 

  • Deep transverse perineal muscle 
  • Urethrovaginal sphincter 
Deep transverse perineal muscle, view from below

The deep transverse perineal muscle runs horizontally from the left and right sides of the pelvic bone arch and extends from in front of the urethra to the perineum. The deep and superficial transverse perineal muscles are separated by a collection of dense, tough fasciae called the perineal membrane.

In addition to providing support for the pelvic floor, the deep transverse perineal muscle also helps to expel the last drops of urine from the urethra. Having a weak deep transverse perineal muscle could lead to urinary tract infections if all of the urine cannot be pushed out of the urethra by this muscle. 

The other muscle in the second layer of the pelvic floor is the urethrovaginal sphincter. The urethrovaginal sphincter is the second external urethral sphincter and it wraps around both the urethra and vagina. Contracting this muscle leads to a contraction of both the urethra and vagina.

However, this muscle is also NOT the muscle that should be voluntarily contracted when doing a proper kegel exercise.

Layer 3: Pelvic Diaphragm 

The pelvic diaphragm is the star of the show when it comes to pelvic floor health. The pelvic diaphragm is the third deepest layer of the pelvic floor which puts it at the very center of all the other muscles. Whenever someone talks about the pelvic floor in general, they are probably talking about these 5 muscles: 

  • Pubococcygeus muscle
  • Pubovaginalis muscle 
  • Puborectalis muscle 
  • Iliococcygeus muscle 
  • Ischiococcygeus muscle 

Levator Ani 

These muscles (except the ischiococcygeus muscle) form what is called the levator ani. The levator ani is the central hub of pelvic floor health since the muscles of the levator ani do the lion’s share of supporting our internal organs. 

The pubococcygeus (PC) muscle is the muscle that runs the show in pelvic floor health. The PC muscle extends from the pubic bone to the tailbone and supports the urethra, vagina, and rectum in addition to providing rhythmic contractions during orgasm.

A proper kegel exercise means a full contraction and relaxation of the PC muscle. The PC muscle acts as the “queen bee” of the pelvic floor so when the PC muscle contracts, all the other muscles and sphincters follow along. 

To contract the PC muscle and perform a kegel properly, imagine trying to hold in a fart but without contracting any of the glutes or abdominal muscles. This should lead to a feeling of the perineum being pushed inward and upward and relaxing the PC muscle should feel like a slight lowering of your pelvic floor.

This contraction will also lead to stopping the flow of urine but it utilizes all of the muscles of the pelvic floor unlike contracting only the superficial, outer muscles of the urogenital diaphragm. 

Pubovaginalis muscle

The pubovaginalis muscle is a horseshoe-shaped muscle that wraps around the back of the vagina near the uterus and the front ends of the muscle are attached to the pubic bone at the front of the body. This muscle’s job is to act as a sling to support the vagina and uterus. 

The puborectalis muscle is positioned in the same way as the pubovaginalis muscle except it extends behind the top of the rectum. The puborectalis muscle helps with the voluntary control of bowel movements by supporting and constricting the anal canal.

Puborectalis muscle

This muscle relaxes in a squatting position which can make bowel movements easier and more comfortable. 

The iliococcygeus muscle has left and right parts that extend from the sacrum, the lowest section of the spine, and are attached to the sides of the pelvic bone. This muscle surrounds the pubovaginalis and puborectalis muscles and assists them in pulling the vagina and rectum towards the pubic bone and supporting the pelvic organs. 

The final muscle of the pelvic diaphragm is the ischiococcygeus muscle. While this muscle is technically not part of the levator ani, the ischiococcygeus muscle pulls the coccyx, or tailbone, forward and stabilizes the sacroiliac joint which is the joint between your pelvis and your spine. It also plays an essential role in providing the proper amount of tension to the pelvic floor.

Without the proper amount of tension in the muscles of the pelvic floor, support for the internal organs will decrease which could contribute to prolapse of the internal organs. 

Layer 4: Smooth Muscle Diaphragm 

The smooth muscle diaphragm is comprised of two muscles:

  • Internal urethral sphincter 
  • External urethral sphincter 

The internal urethral sphincter is located on the inside of the urethral tube where the bladder meets the top of the urethra. This muscle is responsible for keeping urine inside the bladder until it is time to use the bathroom.

Unlike the other muscles in the pelvic floor which are skeletal muscles and can be contracted voluntarily, the internal urethral sphincter is a smooth muscle and cannot be controlled voluntarily or trained with pelvic floor exercises. This means that it is all the more important to strengthen the voluntary muscles of the pelvic floor. 

The external urethral sphincter is the third and final external urethral sphincter. This muscle wraps only around the urethra and attaches to the pelvic bone. This muscle is voluntarily relaxed to expel urine when using the bathroom and it contracts to prevent urine leakage.

A strong pelvic floor as a whole leads to stronger external urethral sphincters which are important for controlling urinary incontinence. 

Layer 5: Endopelvic Fascial Diaphragm 

The endopelvic fascial diaphragm is the deepest of the five layers of the pelvic floor. This system of connective tissue has also been called the upper pelvic fascial floor and it covers the levator ani muscles, surrounds the pelvic organs such as the bladder, urethra, uterus, and ovaries, and suspends them from the pelvis. 

Excessive stretching or tears in the fascia leads to a loss of support for the pelvic organs and could lead to prolapse. The proper strengthening and contraction of the muscles in the other layers of the pelvic floor helps to counteract overstretching of the fascia. 

As you can see, each of the 14 muscles of the pelvic floor has a job to do and every muscle is vital to the overall health of our pelvic floor. Since the majority of these muscles can be contracted voluntarily, this gives us nearly complete control of our pelvic floor health even though the pelvic floor muscles are not entirely visible to us.

The muscles in the pelvic floor are not unlike the other muscles in our body that we use for exercise so you can see great improvements with urinary incontinence as well as your sex life through proper exercise and progressive resistance training of the pelvic muscles.


This post originally appeared on the Intimina Blog.

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