Pelvic Cavity & Organs Pelvis & Perineum Unit Lecture 2 د. حيدر جليل الأعسم
Pelvic Cavity Pelvic cavity, or cavity of the true pelvis, can be defined as the area between pelvic inlet and pelvic outlet. It is customary to subdivide it by pelvic diaphragm into: • Main pelvic cavity above • Perineum below Contents of the main pelvic cavity: • Anterior Contents (UB, male internal organs & females internal organs) • Posterior Contents ( sigmoid, Rectum)
Posterior Contents of Pelvic Cavity Sigmoid Colon: It is 10 to 15 inches (25 to 38 cm) long and begins as a continuation of descending colon in front of pelvic brim. Below, it becomes continuous with rectum in front of third sacral vertebra. Relations: Anteriorly: In male, urinary bladder; in female, posterior surface of uterus and upper part of vagina Posteriorly: rectum and sacrum. Blood Supply Arteries: Sigmoid branches of inferior mesenteric artery. Veins: drain into inferior mesenteric vein, which joins portal venous system. Lymph Drainage: drains into inferior mesenteric nodes. Nerve Supply: sympathetic and parasympathetic nerves from inferior hypogastric plexuses.
Posterior Contents of Pelvic Cavity Rectum: begins in front of third sacral vertebra as a continuation of sigmoid colon. It passes downward, following anterior concavity of sacrum and coccyx, and ends in front of tip of coccyx by piercing pelvic diaphragm and it is continuous with anal canal. Lower part of rectum is dilated forming rectal ampulla. Puborectalis portion of levator ani muscles forms a sling at junction of rectum with anal canal and pulls this part of bowel forward, producing anorectal angle. Peritoneum covers anterior and lateral surfaces of first third of rectum and only anterior surface of middle third, leaving lower third devoid of peritoneum. Muscular coat of rectumis arranged in usual outer longitudinal and inner circular layers of smooth muscle. Mucous membrane of rectum forms two or three semicircular permanent folds called transverse folds of rectum.
Rectum Relations of rectum: Posteriorly:sacrum and coccyx; piriformis, coccygeus, and levatores ani muscles; sacral plexus; and sympathetic trunks (sacral part, pelvic). Anteriorly: In male, upper 2/3 of rectum is related to sigmoid colon and coils of ileum that occupy rectovesical pouch. Lower 1/3 of rectum is related to posterior surface of bladder, termination of vas deferens and seminal vesicles, and to prostate. In female, upper two thirds of rectum is related to sigmoid colon and coils of ileum that occupy rectouterine pouch (pouch of Douglas). Lower third of rectum is related to posterior surface of vagina.
Rectum Blood Supply Arteries: superior, middle and inferior rectal artery. Veins:Superior, Middle and inferior rectal veins. Lymph Drainage: pararectal nodes and then into inferior mesenteric nodes. Lower part of rectum into internal iliac nodes. Nerve Supply: inferior hypogastric plexuses. Rectum is sensitive only to stretch.
Anterior Pelvic Viscera in Males Ureters Each ureter is a muscular tube that extends from kidney to posterior surface of bladder. It enters the pelvis by crossing bifurcation of common iliac artery in front of sacroiliac joint. Each ureter then runs down the lateral wall of pelvis in front of internal iliac artery to towards ischial spine and turns forward to enter lateral angle of bladder. Near its termination, it is crossed by vas deferens. Ureter passes obliquely through wall of bladder for about (2 cm) before opening into bladder. This intramural part of ureter forms uretero-vesical valve.
Anterior Pelvic Viscera in Males Urinary Bladder: It is situated immediately behind pubic bones within the pelvis. Capacity 500 mL in adults. Bladder has a strong muscular wall. Variable shape? Empty bladder in adults lies entirely within pelvis; Filled bladder rises up into hypogastric region. Empty bladder is pyramidal: Apex of bladder: points anteriorly & lies behind upper margin of symphysis pubis. It is connected to umbilicus by median umbilical ligament (urachus). Base of bladder (Posterior surface): is triangular & faces posteriorly. Superolateral angles are joined by ureters, and inferior angle gives rise to urethra. The Two vasa deferentia lie side by side on posterior surface & separate seminal vesicles from each other. Upper part of posterior surface is covered by Peritoneum (rectovesical pouch). Lower part of posterior surface is separated from rectum by vasa deferentia, seminal vesicles, and rectovesical fascia.
Anterior Pelvic Viscera in Males Superior surface of bladder:is covered with peritoneum and is related to coils of ileum or sigmoid colon. Along lateral margins of this surface, peritoneum passes to lateral pelvic walls. As bladder fills, it becomes ovoid, and superior surface bulges upward into abdominal cavity. Peritoneal covering is peeled off lower part of anterior abdominal wall so that bladder comes into direct contact with anterior abdominal wall. Inferolateral surfaces of bladder:are related in front to retropubic pad of fat and pubic bones. More posteriorly, they lie in contact with obturator internus muscle above and levator ani muscle below.
Anterior Pelvic Viscera in Males Neck of bladderlies inferiorly and rests on upper surface of prostate. Here, smooth muscle fibers of bladder wall are continuous with those of prostate. Neck of bladder is held in position by thickenings of pelvic fascia (puboprostatic ligaments in male; and pubovesical ligaments in female). Mucous membrane of empty bladderis folded that disappear when bladder is full. Trigone is area of mucous membrane covering internal surface of base of bladder and it is always smooth, even when bladder is empty. Superior angles of trigone correspond to openings of ureters, and inferior angle to internal urethral orifice. Ureters pierce bladder wall obliquely, and this provides a valve-like action, which prevents a reverse flow of urine toward the kidneys as the bladder fills.
Anterior Pelvic Viscera in Males Trigone is limited above by a muscular ridge, which runs from opening of one ureter to the other (interureteric ridge). Uvula vesicaeis a small elevation situated immediately behind urethral orifice, which is produced by underlying median lobe of prostate. Muscular coat of bladderis composed of smooth muscle arranged in 3 layers of interlacing bundles (detrusor muscle). At neck of bladder, circular part of muscle coat is thickened forming sphincter vesicae. Blood Supply: Arteries: Superior and Inferior vesical arteries, branches of internal iliac arteries. Veins:form vesical venous plexus which drains into internal iliac vein. Lymph Drainage: Internal & external iliac nodes Nerve Supply: inferior hypogastric plexuses. Sympath=contienence,Parasympapth=urination