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Anatomy Ch 4 307-316 Case 4 Anatomy Ch 4 307-316 Large Intestine -large intestine absorbs fluids/salts from gut, is 1.5m long; consists of cecum, appendix, colon, rectum, and anal canal. -begins at right groin (with appendix) and continues as ascending colon into R hypochondrium -colon bends to the left forming R colic flexure (hepatic) and becomes tranverse colon to L hypochondrium, where it bends at the spleen (L colic flexure, or splenic flexure) and continues as descending colon through left flank and groin -enters pelvic cavity as the sigmoid colon, continues on the posterior wall as rectum, and terminates as anus Characteristics are: -large diameter, peritoneal-covered accumulations of fat (omental appendices)= colon -segregation of longitudinal muscle into 3 narrow bands (taeniae coli) -sacculations of colon (haustra of colon) Cecum and Appendix – cecum 1st part of large intestine, is an intraperitoneal structure and is continuous with ascending colon at entrance of ileum; in contact with anterior ab wall -appendix is narrow, hollow, blind-ended tube connected to cecum and has large aggregations of lymphoid tissue in its walls; suspended from ileum by mesoappendix which has appendicular vessels -surface projection of the appendix is junction of lateral and mid-1/3 of line from ant sup iliac spine to umbilicus (McBurney’s Point) -arterial supply to cecum and appendix include: (1) ant cecal artery from ileocolic artery (from superior mesenteric), (2) posterior cecal artery from ileocolic, (3) appendicular artery from ileocolic) Appendicitis – acute appendicitis occurs when appendix is obstructed by fecalith or enlargement of lymph nodes, and bacteria can proliferate to cause inflammation -pain begins as central periumbilical pain and then moves to iliac fossa Colon – extends superiorly from cecum, and consists of ascending, tranverse, descending, and sigmoid colon -ascending and descending colon = RETROperitoneal, transverse and sigmoid = INTRAperitoneal -L colic flexure attached is attached to diaphragm by phrenicolic ligament -immediately lateral to ascending and descending colons are R and L paracolic gutters where materials can pass from one region of peritoneal cavity to another (lack major vessels) -sigmoid colon begins above pelvic inlet and extends to the level of SIII, continuous with rectum -arterial supply to ascending colon is: colic branch of ileocolic artery, anterior/posterior cecal arteries, R colic artery from superior mesenteric -arterial supply to the transverse colon is: R colic a., middle colic a., L colic a. from inf mesenteric -descending colon includes L colic from inferior mesenteric -sigmoid colon includes sigmoidal arteries from inferior mesenteric artery Rectum and Anus – rectum extends from sigmoid colon anus and is at SIII (retroperitoneal) -arterial supply to rectum and anal canal: superior rectal artery from inferior mesenteric, middle rectal artery from superior mesenteric, inferior rectal artery from internal pudendal artery from internal iliac artery Anatomy Ch 4 307-316 Case 4 Malrotation of Midgut Volvulus – malrotation is incomplete rotation and fixation of midgut after it passes from umbilical sac and returned to abdominal coelom -suspensory muscle of duodenum (ligament of Treit) – attaches small bowl mesentery to duodenum; mesentery prevents accidental twists of gut -if duodenojejunal flexure or cecum does not end up at usual site, it shorten mesentery and permit twisting (Volvulus), may lead to infarction -some patients have their cecum ending in midabdomen, and a series of peritoneal folds known as Ladd’s Bands develop that extend to R surface of liver and compress duodenum Bowel Obstruction – mechanical obstruction is due to foreign body, tumor, extrinsic compression, or embryological band -a functional obstruction is due to an inability of bowel to peristalse -primary symptom is central abdominal, intermittent pain as peristaltic waves try to overcome obstruction -vomiting and absolute constipation may ensue -bowel continues to distend, compromising blood supply within wall leading to ischemia -small bowel obstruction typically due to adhesions from surgery, hernias, or volvulus -large bowel obstruction is commonly caused by a tumor, or hernia, or diverticula -treatment is intravenous replacement of fluid and electrolytes, analgesia, and relief of obstruction Diverticular Disease – development of colonic diverticula in sigmoid colon, where intraluminal pressure is the highest -patients develop symptoms when neck of diverticulum becomes obstructed by feces and becomes infected, to cause diverticulitis Ostomies – surgically externalizing bowel to anterior abdominal wall: Gastrostomy – performed when stomach is attached to anterior abdominal wall and a tube is placed through the skin into the stomach to feed patient Jejunostomy – jejunum is brought to anterior abdominal wall and fixed, where feeding tube is inserted through anterior abdominal wall Ileostomy – when small bowel movements need to be diverted from distal bowel, often performed to protect a distal surgical anastomosis Colostomy – performed to protect distal large bowel after surgery or large bowel obstruction, and a colostomy would allow decompression of bowel and its contents Ileal Conduit – after resection of bladder for tumor; a short segment of bowel is identified and divided twice to produce 20cm segment of small bowel on its own mesentery and used as a conduit, and remaining bowel is joined together -used when patients have an ileostomy or colostomy