TBL19 - Colon and Appendix Flashcards
What enables easy recognition of the colon during surgery?
The omental (epiploic) appendices and haustra enable easy recognition of the colon during surgery
Describe the location of the appendix. Define the McBurney point. How does the McBurney point help with identification of location of the appendix?
1) The appendix is a blind diverticulum from the posteromedial aspect of the cecum
2) McBurney’s point is located 1/3 from ASIS and 2/3 from the umbilicus
3) It is a surface indicator for the appendix in the lower right quadrant of the abdominal cavity
Why does pain from appendicitis usually commence as vague umbilical pain and become sharp pain localized in the lower right quadrant?
1) When secretions from the appendix cannot escape, the appendix swells, stretching the visceral peritoneum
2) The pain of appendicitis usually commences as a vague pain in the peri-umbilical region because afferent pain fibers enter the spinal cord at the T10 level
3) Later, severe pain in the right lower quadrant results from irritation of the parietal peritoneum lining the posterior abdominal wall
Name respective branches of the SMA that supply the cecum, appendix, ascending colon, and transverse colon. List the branches of the IMA that supply the descending colon, sigmoid colon, and rectum.
1) SMA branches:
a) Middle colic artery: transverse colon
b) Right colic artery: ascending colon
c) Ileocolic artery: ileum, cecum, and ascending colon
2) IMA branches:
a) Left colic artery: descending colon
b) Sigmoid artery: descending and sigmoid colon
c) Superior rectal artery: proximal part of rectum
Describe the series of anastomotic arcades that form the marginal artery of the colon.
1) The arterial supply to the ascending colon and right colic flexure is from branches of the SMA, the ileocolic and right colic arteries
2) These arteries anastomose with each other and with the right branch of the middle colic artery, the first of a series of anastomotic arcades that is continued by the left colic and sigmoid arteries to form a continuous arterial channel, the marginal artery (juxtacolic artery)
3) This artery parallels and extends the length of the colon close to its mesenteric border
Where does lymph from the midgut and hindgut derivatives drain into? Where does efferent lymph from the mesenteric nodes empty into?
1) Lymph from the midgut and hindgut derivatives drains into the superior and inferior mesenteric lymph nodes, respectively
2) Like the celiac nodes of the foregut derivatives, efferent lymph from the mesenteric nodes empties into the thoracic duct
What does the transverse mesocolon enable and where does it hang? What does the sigmoid mesocolon enable and where is it found?
1) The transverse mesocolon enables free mobility of the transverse colon and it usually hangs to the level of the umbilicus
2) Although the sigmoid mesocolon affords mobility to the sigmoid colon, it typically remains in the left lower quadrant
During development where do the ascending and descending portions of the colon protrude into and do they protrude fully? What is a result of this?
1) During development, the ascending and descending portions of the colon only protrude partially into the parietal peritoneum
2) Thus, visceral peritoneum covers their anterior and lateral surfaces but mesenteries do not form
What is different between the ratio of absorptive cells to goblet cells in the colon as compared to in the small intestine? What does this result in?
1) The ratio of absorptive cells to goblet cells is significantly less in the colon than the small intestine
2) Thus, a rich mucus secretion protects and lubricates the colonic epithelial surface
What is absorbed across the epithelium of the colon? What is involved in nonenzymatic digestion along the apical surface of the epithelium of the colon?
1) Water and electrolytes are absorbed across the epithelium of the colon
2) A vast bacterial population on the apical surface of the epithelium of the colon is engaged in nonenzymatic digestion
What does the muscularis externa of the colon consist of? What is found within the taeniae coli?
1) The muscularis externa of the colon consists of an inner circular layer of smooth muscle and an outer longitudinal layer of nonuniform thickness
2) The taeniae coli is made up of three equidistant longitudinal bands of smooth muscle interconnected by a thin layer of longitudinal smooth muscle
What are the haustra formed by? What are the omental (epiploic) appendices and what do they form?
1) The haustra are formed by tonic contraction of the taeniae coli
2) The omental (epiploic) appendices are pockets of white fat in the serosa that form intermittent, pendulous bulges covered by visceral peritoneum
What does the wall of the appendix resemble? Define the role of the appendix.
1) The wall of the appendix resembles that of the colon except the appendix lacks taeniae coli and contains a discontinuous ring of lymphoid nodules in the submucosa
2) The appendix has been assumed to be vestigial, but abundant lymphoid tissue in its wall and production of B-lymphocytes in germinal centers of nodules imply an immunologic defense function
What are the early symptoms of diverticulitis and when would surgical treatment be required?
1) Inflammation of diverticula, or diverticulitis, can lead to perforations, tears, bleeding, and infection
2) Early symptoms are cramps, bloating, and constipation, often followed by blood in the stool
3) Antibiotic treatment is usually successful, but severe cases may need surgery
How do histologic changes during the pathogenesis of appendicitis correlate with the accompanying sensations of visceral and somatic pain?
1) Appendicitis—inflammation of the appendix—is caused by obstruction of the narrow lumen, which increases susceptibility to bacterial infection. Pain in the lower right quadrant, nausea, and vomiting result
2) Acute appendicitis first affects the mucosa, where edema and leukocyte infiltration occur
3) Penetration of other layers may lead to abscess, necrosis, perforation into the peritoneal cavity, and a complication— peritonitis (inflammation of the peritoneum)
