Histology Of The Lower GI Tract Flashcards
What are the 4 degree of folding?
What is their purpose?
Plicae circularis
Intestinal villi
Intestinal glands (Crypts of Leiberkuhn)
Micro villi on enterocytes
Increase surface area
Where does Plicae circularis begin?
Where does it disappear?
Duodenum
Mid-ileum
What do villi form?
Where do they end?
Crypts of Liberkuhn
Muscularis mucosae
What are Crypts of Lieberkuhn?
What kind of cells are in the crypts?
Simple tubular glands that increase s.a.
Absorptive, goblet, Paneth, and enteroendocrine cells
Where is the muscularis mucosa located?
Between mucosa and submucosa
What is serosa?
Thin layer of loose CT covered by visceral peritoneum (mesothelium)
What is mesothelium?
Membrane of simple squamous cells that forms the lining of several body cavities
What is the purpose of segmentation?
What controls it?
Mix food w/chyme
ANS
Where is the site of of blood and lymphatic flow?
Intestinal submucosa
Arterioles from the submucosal plexus create what 2 capillary networks?
Villus capillary plexus supplies intestinal villus and upper crypts of Lieberkuhn
Pericryptal capillary plexus supplies lower half
Where are lacteals located?
What are they?
What is their circulation
Centrally located within a villus
Convey chyle packaged in chylomicrons
Intestine to lymph to thoracic duct to systemic blood
What distinguishes the duodenum?
Brunner’s glands in submucosa
Few goblet cells
What distinguishes the Jejunum?
Well-developed Plicae circularis
Irregular villi
No glands/patches
What distinguishes the ileum?
Lots of lymphoid nodules (Peyer’s Patches) in LP and submucosa
Finger like villi
Goblet cells
What enzymes are in the enterocytes?
What is their purpose?
How are they transported?
Lactase, Maltese, sucrase
Terminal digestion of carbs to reduce them to hexoses
Carrier proteins
What is the secretory products of goblet cells?
How are they released?
Purpose?
Glycoproteins (80% carbs, 20% proteins)
Exocytosis
Protective gel against bacterial invasion
What do Paneth cells do?
What is their mechanism?
Secrete antimicrobial proteins to limit bacteria contact
Kill bacteria by enzymatic degradation of the bacterial wall or disrupting inner membrane
What part of the gut does Crohn’s disease affect?
Terminal ileum
Large intestine
What is the cause of the initial alteration of the intestinal mucosa in Crohn’s disease?
Result?
Neutrophils into the Crypts of Lieberkuhn
-occlusion of the lumen by fibrosis and fistula formation of other segments in the small intestine
What bacteria is commonly treated with FMT?
What is the purpose?
C. diff which causes diarrhea
Replace good bacteria that has been killed or suppressed
What is the major function of the large intestine?
Transport of ions and water
What forms the large intestine?
Cecum and appendix –> asc, trans, desc colon –> sigmoid colon –> rectum –> anus
What kind of epithelium lines the large intestine?
Formed by what?
What is not found in the large intestine?
Simple columnar
Enterocytes and goblet cells
Plicae circularis and villi
What do glands of Lieberkuhn contain?
What is not present?
Goblet, enteroendocrine, and stem cells
Paneth cells
What forms taeniae coli?
What do contractions produce?
Outer smooth muscle layer
Haustra
Describe the appendix:
NO villi, NO taenia coli, lots of lymphoid tissue
thickened wall
Safe house for good bacteria
What kind of epithelium below Pectinate line?
Keratinized stratified squamous
What does the submucosa contain below the Pectinate line?
Sebaceous and sweat glands
Loss of what gene leads to colorectal tumors?
APC (excess of it)
What is chyme mixed with?
Via what mechanism?
HCl, pepsinogen, gastric lipase, intrinsic factor
PIG H
Peristalsis
