Pelvic Floor Muscles

What is the Pelvic Floor

The pelvic floor, also known as the pelvic diaphragm, is a muscular structure that forms the lower boundary of the pelvic cavity — one of the five primary body cavities in the human body. Located at the base of the torso, the pelvic cavity houses the pelvic organs, including the bladder, rectum, colon, uterus, and prostate gland.

Structurally, the pelvic floor is composed of muscles, ligaments, and fascia that collectively support pelvic viscera, regulate continence, assist in childbirth, and maintain intra-abdominal pressure.

The muscles forming the pelvic floor are grouped as the “pelvic muscles” and are among the core muscles of the body. But before exploring them in more detail, it’s important to first understand the structures of the pelvis and pelvic cavity.

Location and Borders of the Pelvic Cavity

Anatomically, the bony pelvis is divided into two regions: the greater (false) pelvis, located above the pelvic brim, and the lesser (true) pelvis, located below it. The greater pelvis supports the lower abdominal organs, while the lesser pelvis encloses the pelvic cavity.

The pelvic cavity is a bony and muscular basin at the base of the torso. Its superior border is defined by the pelvic brim, running from the pubic bone at the front to the sacral promontory at the back. Inferiorly, it ends at the level of the ischial tuberosities and the coccyx. Structures below this level are part of the perineum.

Walls of the Pelvic Cavity

• Anterior Wall: Formed by the bodies of the pubic bones and the pubic symphysis.
• Lateral Walls: Made up of the ilium and ischium bones, along with the obturator internus muscle, which lines the inner surface of the lateral wall.
• Posterior Wall: Bony support comes from the sacrum and coccyx, while the piriformis muscle occupies much of the soft tissue space.

The pelvic floor, forming the inferior wall or boundary of the cavity, consists not only of muscles but also supporting ligaments and fascia that help anchor and stabilize the pelvic contents.

Layers That Reinforce the Pelvic Floor

The pelvic floor is reinforced from below by layers of muscles and fascia to help with its functions. Here are the layers, from superficial to deep:

1. Perineum: It is the most superficial part of the pelvic outlet, lying between the thighs. The perineum supports the deeper pelvic floor and plays a role in urination, continence, and sexual function.
2. Urogenital Diaphragm: Situated anteriorly, this layer includes fascia and connective tissue that reinforce the pelvic floor and provide support to urogenital structures. It plays a key role in urinary continence.
3. Pelvic Floor (Pelvic Diaphragm): The deepest and most important layer in terms of support, it consists of muscles that form a bowl-like structure.

Name, Location, Anatomy, and Functions of the Muscles of the Pelvic Floor

While some sources include all three above-mentioned layers as part of the pelvic floor, this broader definition is more common in clinical settings, like physical therapy and rehabilitation. Anatomical literature typically defines the pelvic floor more narrowly, limiting it to only the muscles that form the pelvic diaphragm. Though functionally related, the perineal muscles are usually categorized separately and not considered part of the “true” pelvic floor in strict anatomical terms.

Here is a list of the muscles that form the pelvic diaphragm, with their location and basic anatomy:

Name	Location	Origin	Insertion	Action	Innervation	Blood Supply
Levator Ani Group	Funnel-shaped structure occupying most of the pelvic floor	–	–	As a whole, these muscles help in — Stabilizing the pelvis— Supporting the pelvic viscera — Contributing to sexual functions(Each muscle has its individual functions as well)	–
— Iliococcygeus	The most posterior muscle in the group, stretching from the pubic bone to the coccyx	Inner surface of the ischium bone, posterior part of the obturator fascia	Coccyx, anococcygeal raphe	— Supporting the pelvic floor — Reinforcing the anococcygeal raphe, which anchors pelvic muscles and fascia	Sacral spinal nerve 3-4 (S3-S4), pudendal nerve	Inferior gluteal, inferior vesical, and pudendal arteries
— Pubococcygeus	Stretches from the pubic bone to the coccyx, running horizontally along both sides of the rectum	Inferior pubic rami, anterior part of the obturator fascia	Coccyx, anococcygeal raphe	— Helping with urinary control — Managing intra-abdominal pressure — Supporting the vagina (pubovaginalis) or prostate (puboprostaticus) and their functions	Sacral spinal nerve 3-4 (S3-S4), pudendal nerve	Inferior gluteal, inferior vesical, and pudendal arteries
— Puborectalis	U-shaped muscle, looping around the rectum to form a sling	Pubic symphysis, superior fascia of the urogenital diaphragm	Anococcygeal raphe	— Works with the external and internal anal sphincters to control bowel movements	Sacral spinal nerve 3-4 (S3-S4), pudendal nerve	Inferior gluteal, inferior vesical, and pudendal arteries
Coccygeus (Ischiococcygeus)	Behind the levator ani, forming the posterior part of the pelvic floor	The top of the ischial spine	Sacrum, coccyx	— Supporting the pelvic viscera — Flexing the coccyx to prevent organ prolapse — Helping the levator ani control urination and defecation when the abdominal pressure is high (e.g., coughing, sneezing).	Sacral spinal nerve 4-5 (S4-S5)	Inferior gluteal, inferior vesical, and pudendal arteries

Each of these muscles exists as a pair, with one on either side of the body.

These muscles are lined superiorly by the endopelvic fascia, a layer of connective tissue that envelops the pelvic organs and anchors them to the pelvic walls and floor.

Hiatuses of the Pelvic Floor

To allow passage to several key structures, the pelvic floor contains two significant gaps or hiatuses:

• Urogenital hiatus: Located at the front, this gap allows the passage of the urethra, and in females, also the vagina.
• Rectal hiatus: Positioned posteriorly, this opening provides passage to the anal canal which connects the rectum to the anus.

Between these two openings lies a fibromuscular structure called the perineal body, which serves as a central point of attachment for several pelvic floor and perineal muscles, effectively linking the pelvic floor to the perineum.