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
The mucosal layer of the intestine is formed by what cells and has what two layers?
- goblet cells
- -outer layer of microorganisms
- -inner layer of antimicrobial proteins (paneth, enterocytes, goblet cells)
What are the permanent structures of the GALT?
appendix
- peyer’s patches
- mesenteric lymph nodes
What cells types are located in the intestine?
lymphocytes, neutrophils, eosinophils that migrate in and out of the area
What cells are contained in the Peyer’s patches?
B and T cells
What are high endothelial venules in the peyer’s patches used for?
lymphocytes use for entry into lymphoid organ into the blood stream
What is the primary purpose of the M cells (microfold) cells in the peyer’s patches?
-test particulate antigens and present them to antigen-presenting cells in lamina propria
What is the primary immunoglobulin formed by GALT?
-IgA that is secreted to coat the microorganisms, but not to stimulate the complement system
Rapid cell turnover is a protective mechanism of the GI tract of what epithelium?
- stomach and small intestine (5 day replacement)
- esophagus and anus: form in basal lamina and migrate to slough off into the lumen
- small intestine: new cells form in the crypts of undifferentiated cells.
Neoplasm
cells that grow at abnormal rates without control. are able to migrate and can locate elsehwere, contributing to cancer
Goblet cells can act as stem cells and replace all types of cells in that area of the intestine
lecture material
Rapid cell turnover in the large intestine and in the stomach arise what what areas?
-large intestines: no villi and the proliferative part is in base of crypts
- stomach: stem cells are located in the neck of gastric glands
- -form enteroendocrine, parietal cell, chief cells
What helps digest carbohydrates when they enter the mouth?
amylase hydrolyzse starch to disaccharides
-also present in the pancreas
Where are disaccharides further degraded to monosaccharides?
- the brush border of small intestine
- -enterocytes then absorb the monosaccharides
The stomach is the first place, what complex begins degradation?
-proteins broken down to peptides with use of pepsin activated by low pH
Trypsin, chymotrypsin, elastase, carboxypeptidase are secreted where?
-secreted from the pancreas and are activated by cells lining the duodenum (enteropreptidase)
True or False:
Cholecystokinin acts in the duodenum in response to the gastric contents as they enter
True
What does cholecystokinin act to do in the duodenum?
- contracts the pyloric sphincter to slow emptying
- stimulate bile and pancreatic enzyme release
- competes with gastrin
Where is gastrin secreted?
-pyloric-antral portion of stomach
What does gastrin function to do in the pyloric section of the stomach?
- stimulate HCl secretion from gastric parietal cells
- growth of gastric mucosa
- stimulates gastric motility
- releases insulin by pancreatic cells
Where is secretin released?
-epithelial cells of duodenum when acid contacts small intestine
Does secretin release pancreatic insulin, and bicarbonate release from the pancreas?
yes
What really marks the transition point that is derived from ectoderm and endoderm?
The pectinate line which is formed from the valves contained on the anal columns
What defect happens that results in the formation of hemorrhoids?
-over dilation of the internal and external hemorrhoid plexus creates a bulge under the mucosa
What describes the best visual picture of the olfactory mucosa?
-pseudostratified columnar without goblet cells and no basement membrane
What is not necessary part of the respiratory membrane?
- dust cells
- -respiratory membrane refers to the membrane between the alveoli and the alveolar capillary
What is characteristic of arterioles?
thick tunica media in relation to size of the lumen
Where does the majority of erythrophagocytosis occur in the body?
billroth cords in the spleen
- spleen is major site of of RBC destruction.
- -The marginal zone of the spleen is just the transition zone between the red and white pulp.
Describe the flow or RBC through the spleen.
splenic artery–>trabecular artery–> central artery–> penicillus–> venous sinusoids
The simple cuboidal epithelium of this portion of the kidney tubule is composed of cells in the form of truncated pyramids which characterized by basal striations that mark the location of mitochondria.
proximal convoluted tubule
Renin is secreted from where?
juxtaglomerular cells
