Gastrointestinal Tract II Flashcards
Understand the morphological features that increase small intestinal surface area.
Plicae circularis (valves of Kerckring) are permanent transverse circular folds of mucosa and submucosa that increase surface area 2-3 times.
Villi are finger-like or leaf-like projections of the surface epithelium and lamina propria that increase surface area 10 times.
Microvilli are projections of the apical plasma membranes that increase surface area 20 times.
List the landmarks that distinguish the duodenum from the ileum.
Duodenum has Brunner’s glands in the submucosa.
Ileum has the longest villi and the highest number of goblet cells. Peyer’s patches are unique to the ileum.
What is the function of Brunner’s gland?
Duodenum has Brunner’s glands in the submucosa. These glands are mostly of the mucous type and secrete an alkaline mucous that helps protect against stomach acid and provide an optimum pH for pancreatic enzyme action.
What is the function of absorptive cell?
Disaccharidases and peptidases are secreted by the absorptive cells and bind to microvilli where they produce monosaccharides and amino acids for absorption.
Lipids are absorbed and reesterified to triglycerides, converted into chylomicrons, and released from lateral surfaces into the lamina propria where they are absorbed by the central lacteals.
Has a striated border
What is the function of goblet cell?
Unicellular glands that produce acid glycoproteins of the mucin type that lubricate and protect the small intestine.
Less abundant in the duodenum and increase in number as one approaches the ileum.
What is the function of Paneth cell?
Exocrine cells found in small groups at the base of crypts.
The apical cytoplasm is filled with large, eosinophilic granules of lysozyme that has antibacterial activity which controls intestinal flora.
These eosinic granules consist of several anti-microbial compounds and other compounds that are known to be important in immunity and host-defense.
What is the function of the crypt of Lieberkuhn?
The crypts of Lieberkuhn (intestinal glands) are simple tubular glands that extend from the surface epithelium down to the muscularis mucosae.
Describe an M (microfold) cell. Understand the role of the M cell in GALT.
Only found in the ileum.
Specialized epithelial cells that cover Peyer’s patches.
Peyer’s patches in the ileum are groups of 20-40 lymphatic nodules covered by M cells. Antigens from the lumen are taken up by the M cells and delivered to lymphocytes and other cells in the Peyer’s patches.
IgA synthesized by plasma cells.
What morphological features distinguish the colon from the rectum or the appendix?
In the cecum & colon: there is taena coli but not in rectum or appendix
What structural modifications found in the small intestine facilitate the absorptive process?
The function of the plicae circulares, the villi and the microvilli is to increase the amount of surface area available for the absorption of nutrients.
Stem Cells are located near the base of the intestinal _______.
Stem Cells are located near the base of the intestinal crypts.
