Download Anatomy Ch 4 307-316

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