Pelvic Floor Anatomy

Original Editor - Venus Pagare

Top Contributors - Laura Ritchie, Venus Pagare, Admin, Kim Jackson, Redisha Jakibanjar, Deborah Mazzarotto, Siobhán Cullen, Uchechukwu Chukwuemeka, Evan Thomas, Scott Buxton, George Prudden, Tarina van der Stockt, Mandy Roscher and Khloud Shreif  

Introduction

• The bony pelvis is composed of sacrum, ileum, ischium, and pubis.
• It is divided into the false (greater) and true (lesser) pelvis by the pelvic brim.
• The sacral promontory, the anterior ala of the sacrum, the arcuate line of the ilium, the pectineal line of the pubis and the pubic crest that culminates in the symphsis pubis.
• The shape of the female bony pelvis can be classified into four broad categories: gynecoid, anthropoid, android, and platypelloid.

3 Layers

The pelvic floor consists of three muscle layers:

1. Superficial perineal layer: innervated by the pudendal nerve

• Bulbocavernosus
• Ischiocavernosus
• Superficial transverse perineal
• External anal sphincter (EAS)
  

2. Deep urogenital diaphragm layer: innervated by pudendal nerve

• Compressor urethera
• Uretrovaginal sphincter
• Deep transverse perineal

3. Pelvic diaphragm: innervated by sacral nerve roots S3-S5

• Levator ani: pubococcygeus (pubovaginalis, puborectalis), iliococcygeus
• Coccygeus/ischiococcygeus
• Piriformis
• Obturator internus

Pelvic Diaphragms

• The pelvic diaphragm is a wide but thin muscular layer of tissue that forms the inferior border of the abdominopelvic cavity.
• Composed of a broad, funnel-shaped sling of fascia and muscle, it extends from the symphysis pubis to the coccyx and from one lateral sidewall to the other.
• The urogenital diaphragm, also called the triangular ligament, is a strong, muscular membrane that occupies the area between the symphysis pubis and ischial tuberosities and stretches across the triangular anterior portion of the pelvic outlet.
• The urogenital diaphragm is external and inferior to the pelvic diaphragm.

Ligaments

The pelvic ligaments are not classic ligaments but are thickenings of
retroperitoneal fascia and consist primarily of blood and lymphatic vessels, nerves, and fatty
connective tissue. Anatomists call the retroperitoneal fascia subserous fascia, whereas surgeons
refer to this fascial layer as endopelvic fascia. The connective tissue is denser immediately
adjacent to the lateral walls of the cervix and the vagina. The broad ligaments are a thin,
mesenteric-like double reflection of peritoneum stretching from the lateral pelvic sidewalls to
the uterus. The cardinal, or Mackenrodt's, ligaments extend from the lateral aspects of the uppe