Pelvic Diaphragm Anatomy

Overview of the Perineum

• The perineum is a shallow compartment lying inferior to the pelvic cavity at the plane of the pelvic outlet
• It is separated from the pelvic cavity by the pelvic diaphragm, which provides muscular support for the abdominopelvic cavity, particularly in seated positions

Boundaries and Geometry of the Perineum

• The perineum is a diamond-shaped region with the following boundaries:
  • Anterior apex: inferior margin of symphysis pubis
  • Posterior apex: tip of coccyx
  • Bilateral apices: inferior point of ischial tuberosities
  • Anterolateral boundaries: ischiopubic rami
  • Posterolateral boundaries: sacrotuberous ligaments
• The perineal body is located at the central point of the diamond, at the midpoint of the line connecting the ischial tuberosities

Urogenital Triangle

• The urogenital triangle is the anterior portion of the perineum
• It accommodates the passage of the urethra and, in females, the vagina
• It is divided into multiple layers, some of which are continuous with the anterolateral abdominal wall
• There are numerous differences between the sexes in the urogenital triangle

Subcutaneous Perineal Fascia

• The subcutaneous perineal fascia is a superficial fascial layer that extends from the anterolateral abdominal wall to cover the urogenital triangle
• It consists of subcutaneous fatty tissue, including Camper's fascia and the ischioanal fat pad
• In females, it forms the mons pubis and labia majora, and in males, it disappears in the scrotal sac to facilitate evaporative cooling of the testes

Superficial Perineal Pouch

• The superficial perineal pouch is an intermediate space bounded by the superficial perineal fascia and the perineal membrane
• It contains the superficial transverse perineal muscle, ischiocavernosus muscle, and bulbospongiosus muscle
• These muscles support the pelvic floor and play a role in urinary and fecal continence, as well as erectile function

Deep Perineal Pouch

• The deep perineal pouch is a space superior to the superficial perineal pouch, bounded by the perineal membrane
• It contains the deep transverse perineal muscle, external urethral sphincter muscle, and other structures
• The external urethral sphincter muscle is a circular skeletal muscle layer surrounding the urethra, and is under voluntary control

Anal Triangle

• The anal triangle is the posterior half of the perineum
• It is bordered laterally by the fascial covering of the obturator internus muscle and is open inferiorly posterior to the transverse perineal muscles
• It is a fat-filled space that provides cushioning and protection for soft tissue structures and accommodates expansion of the anal canal during defecation

Ischioanal Fossa

• The ischioanal fossa is a wedge-shaped space formed by the funnel-shaped pelvic diaphragm
• It is divided into left and right sides by the central anal canal

Anal Canal

• The anal canal is the terminal portion of the digestive tract
• It is surrounded by the internal and external anal sphincters, which are under autonomic and voluntary control, respectively

Pelvic Diaphragm

• The pelvic diaphragm is a dome-shaped roof of the perineum
• It is formed by the coccygeus and levator ani muscles, which provide support for the pelvic cavity and organs
• The levator ani muscle is a collection of poorly separated muscular bands that make up the majority of the pelvic diaphragm

This quiz covers the anatomy of the pelvic diaphragm, its location, and its functions in supporting the abdominopelvic cavity.