TBL19 - Jejunum and Ileum Flashcards
How long are the jejunum and ileum together and what do they occupy? What are the jejunum and ileum attached to and by what?
1) The jejunum and ileum, which together are 6-8 m long, occupy portions of all four abdominal quadrants
2) The jejunum and ileum are attached to the posterior abdominal wall by the mesentery of the small intestine, a derivative of the dorsal mesentery
Where do intestinal branches of the retroperitoneal SMA course and what do they supply? Within the mesentery, what do intestinal branches form? What supplies capillaries in the walls of the jejunum and ileum?
1) Intestinal branches of the retroperitoneal SMA course within the mesentery to supply the jejunum and ileum
2) Within the mesentery, the intestinal branches form loops or arcades
3) Straight branches (aka vasa recta) from the arcades supply capillaries in the walls of the jejunum and ileum
What are arterial arcades and vasa recta associated with? How do surgeons use these distinctions?
1) The arterial arcades and vasa recta are associated with the jejunum and ileum
2) In the jejunum, there are fewer, broader arcades with longer vasa recta
3) In the ileum, there are more numerous, thinner arcades with shorter vasa recta
What are the symptoms of ileus, how can it be diagnosed early, and how is early diagnosis related to treatment?
1) Occlusion of the vasa recta by emboli (e.g., blood clots) results in ischemia of the part of the intestine concerned. If the ischemia is severe, necrosis (tissue death) of the involved segment results and ileus (obstruction of the intestine) of the paralytic type occurs
2) Ileus is accompanied by a severe colicky pain, along with abdominal distension, vomiting, and often fever and dehydration
3) If the condition is diagnosed early (e.g., using a superior mesenteric arteriogram), the obstructed part of the vessel may be cleared surgically
What is the frequency of an ileal (Meckel) diverticulum and where is visceral pain from an inflamed diverticulum referred?
1) An ileal diverticulum (or Meckel diverticulum) is a congenital anomaly that occurs in 1–2% of the population
2) An ileal diverticulum may become inflamed and produce pain mimicking that produced by appendicitis (right lower quadrant)
Where are the plicae circulares more numerous and well developed between the ileum and jejunum?
The plicae circulares are more numerous and well developed in the jejunum
What forms intestinal crypts and what do they do? What covers the muscularis externa?
1) The simple columnar epithelium, which lines the villi of the small intestinal mucosa, dips between the villi to form intestinal crypts that fill the lamina propria and extend to the muscularis mucosae
2) Visceral peritoneum (aka serosa) covers the muscularis externa
What type of cells does the epithelium consist of? Where are capillaries and large lymphatic capillaries found? What do the lacteals and capillaries do?
1) The epithelium consists of goblet cells and absorptive cells (aka enterocytes)
2) Capillaries and large lymphatic capillaries (aka lacteals) are found in the lamina propria
3) Lacteals absorb digested lipids while other digested nutrients are absorbed by the capillaries
Where do paneth cells reside? What do the reddish pink secretory granules in the Paneth cell cytoplasm contain?
1) Paneth cells reside at the base of the intestinal crypts and are especially numerous in the ileum
2) The reddish pink secretory granules in the Paneth cell cytoplasm contain lysozyme
What resides in the ileal submucosa and what does it characteristically occupy?
Extensive MALT resides in the ileal submucosa and characteristically occupies half of the ileal circumference
What provides a main line of defense against pathogen invasion in the ileum?
Antimicrobial actions of Paneth cells and selectively differentiated plasma cells of the MALT provide a main line of defense against pathogen invasion in the ileum
Compare ratios of enterocytes and goblet cells in the three segments of the small intestine. Cite stimuli that cause massive mucous secretion by the goblet cells.
1) Enterocytes are most numerous in upper parts, their number slowly decreasing toward the lower end of the tract. In contrast, the number of goblet cells increases from duodenum to ileum
2) Cholinergic stimulation, as well as bacterial and endotoxin exposure, causes massive mucin release by goblet cells
