Perineum and Urogenital Triangle Anatomy

• The perineum is the region inferior to the pelvic diaphragm and between the thighs
• It is a diamond-shaped area bounded by the pubic symphysis (anteriorly), ischial tuberosities (laterally), and the coccyx (posteriorly)
• An imaginary line joining the ischial tuberosities divides the perineum into two triangles: the urogenital triangle (anteriorly) and the anal triangle (posteriorly)

Urogenital Triangle

• The urogenital triangle includes the external genitalia and the terminal portions of the urethra in both sexes
• In females, the vaginal opening is within this triangle
• The perineal membrane is a strong, fibrous layer spanning this triangle
• The perineal body (central tendon of the perineum) is a fibromuscular mass at the perineum's center, just anterior to the anus, serving as an attachment point for perineal muscles
• Muscles here, like the bulbospongiosus, ischiocavernosus, superficial transverse perineal, and deep transverse perineal muscles, support the pelvic floor, aid urination/defecation, and contribute to sexual function

Anal Triangle

• This triangle contains the anal canal and surrounding structures
• Ischioanal fossae (ischiorectal fossae) are fat-filled spaces lateral to the anal canal and inferior to the pelvic diaphragm, expanding the anal canal during defecation
• The pudendal nerve and internal pudendal vessels pass through the ischioanal fossa

Peritoneal Cavity

• This cavity is the potential space between the parietal and visceral peritoneum
• It contains serous fluid for lubrication, allowing organ movement
• The cavity is closed in males
• In females, it connects to the exterior via the uterine tubes, uterus, and vagina
• The greater omentum is a large peritoneal fold hanging from the greater curvature of the stomach
• The lesser omentum extends between the lesser curvature of the stomach and the liver
• Mesenteries are peritoneal folds attaching intestines to the posterior abdominal wall, providing pathways for blood vessels, nerves, and lymphatic vessels
• Ligaments are peritoneal folds connecting organs or connecting organs to the abdominal wall

Peritoneal Reflections and Spaces

• Peritoneal reflections create compartments within the abdominal cavity
• The greater sac is the main compartment
• The lesser sac (omental bursa) lies posterior to the stomach and lesser omentum, communicating with the greater sac through the omental foramen (foramen of Winslow)
• Paracolic gutters are spaces between the colon and the lateral abdominal wall, facilitating peritoneal fluid flow

Peritonitis

• Peritonitis, or peritoneum inflammation, is often due to bacterial infection from a perforated viscus (e.g., appendicitis, bowel perforation) or trauma
• Symptoms include severe abdominal pain, tenderness, rigidity, and systemic infection signs
• Ascites is the accumulation of fluid in the peritoneal cavity, potentially from liver disease, heart failure, kidney disease, or cancer

Gutters and Mesenteries

• Paracolic gutters and mesenteries are essential for fluid movement and organ attachment within the peritoneal cavity
• The mesentery proper suspends the small intestine
• The transverse mesocolon suspends the transverse colon
• The sigmoid mesocolon suspends the sigmoid colon

Overview of the perineum, the region inferior to the pelvic diaphragm and between the thighs. Divided into urogenital and anal triangles, the urogenital triangle contains external genitalia and urethra. Key structures include the perineal membrane and body, with associated muscles.