Lower GI Tract Flashcards
What are the layers of the intestinal wall from deep to superficial?
- mucosa with lamina propria and muscularis mucosa
- submucosa
- muscularis layer
- serosa
What does the duodenum look like histologically?
- leaflike distal shape
- deep crypts of lieberkuhm (invaginations)
- brunner’s glands in the submucosa
The villi in the jejunum have what generic shape?
- finger like shape and long
- no glands in the submucosa
The villi from the ileum look like what?
- short finger like projections
- contain large lymphoid aggregates making Peyer’s patches.
- -Extend from submucosa into the lamina propria
What are the most common types of cells that are contained in the crypts?
- goblet cells
- enterocytes
The enterocytes of the crypt cells produce disaccharides and what other components?
- enteropeptidase which is needed for activation pacreatic zymogens and proenzymes
- also absorb carbs, proteins, lipids
Where are paneth cells from and what do they do?
- from basal crypt cells
- produce lysosomes that control intestinal flora (eosinophilic in nature)
What cells are similar to unicellular goblet cells, in the intestine?
- enteroendocrine cells that produce paracrine or autocrine secretions
- produce peptide hormone and serotonin
What is the primary function of the glands of brunner that are found in the submucosa of the duodenum?
-form bicarbonate and mucus, in able to regulate gastric acids.
The duodenum means?
- 12 inches, therefore the jejunem is 12 inches long
What are characteristic of cells types of the large intestine?
-contain simple columnar epithelium, and crypts, but do not contain villi
What are the cells types and views of the ileum?
- No glands in submucosa
- crypts of lieberkuhn present
- long and narrow villi
Where are paneth cells located?
- Red appearing cells that are eosiniphilic
- located in the ileum
What are the primary functions of the large intestine?
- secrete mucous
- absorb fluid
- form fecal material
- continue digestion
- goblet cells are most prominent
What are the large characteristics that give rise to the hastra (taneiae coli) in the large intestine?
3 spaced bands of muscle fascicles on the outer longitudinal layer
What are the epiploica appendix?
-small aggregates of adipocytes around the serosa of the large intestine, with an unknown function
Why is the tight junction barrier important to be maintained in the intestine?
-defects will allow for antigens to enter into the lamina propria
A defect occurs in the tight junctions of the intestines, what is possible to happen?
- antigens pass through the junctions to lamina propria
- antigens bind to Toll-like receptors on dendritic cells migrate to mesenteric lymph nodes
- dendritic cells present to immature T cells–> induce T helper and Cytolytic T cells
- Helper T cells, migrate to lamina propria secreting TNF-beta, and Interferon-gamma
- unregulated cytokines signal enterocytes to allow antigens to pass the lamina propria and increasing the inflammatory response which can lead to peritonitus and/or death
What are the functions of the Paneth cells?
- pahocytosis to regulate intestinal flora
- form lysozymes to increase permeability of bacteria
- secrete defensins to increase the permeability of teh target organism
- TNF- alpha
What type of immunity do Paneth cells participate in?
adaptive antimicrobial immunity