lesson 13 gritti Flashcards
3 segments that make up the small intestine
duodenum, jujogenum, ileum
plicae circularis
foldings of the small intestine that include both the mucosa and the submucosa
villi
finger-like projections of the mucosa of the small intestine characterized by simple columnar epithelium. epithelial cells have apical projections called microvilli.
lacteal
each villus in the small intestine contains a central lacteal (lymphatic capillary) for the absorbance of lipids
how many layers of smooth muscles do we have in the small intestine?
2, one encircling the submucosa and the other runs lengthwise to the serosa->this allows for strong peristaltic movements
fenestrated capillaries, where in the small intestine?
in the lamina propria of each villus, to aid absorption
crypts of lieberkuhn or intestinal glands
invaginations between villi extending till the muscolaris mucosa
enterocytes
-columnar cells with microvilli (brush border) that are responsible for absorbance of nutrients
-tall columnar nuclei disposed either at the center of the cell or basally
-brush boarders are covered by glycocalix: a mucopolysaccharide matrix
goblet cells
-mucous secreting cells, essential for lubrification of intestinal content and to protect the epithelium
-the number of cells increase as going down from the first tract of the small to the large intestine
stem cells
at the base of the intestinal gland (crypt), migrate and renew the epithelium
paneth cells
-at the base of the crypt with stem cells, they secrete antimicrobial substance->relevant in defense
-have secretory granules in the apical cytoplasm fill with antimicrobial substance, enzymes..etc
-in response to intestinal insults they can acquire stem cell properties and help in tissue repair
-long lived (20 days)
-protect stem cells from injuries and pathogens
-control microbial lumen density
tuft cells
sentinels that trigger type 2 immunity to parasites
fixed number of paneth cells in one crypt
5-12
intestinal enteroendocrine cells
-similar to the other enteroendocrine cells present in the GI tract
-part of the crypt
-secrete peptide hormones
-granules are in the basal part because the hormones have to be released in the blood
M cells
-cells that sense the pathogen, take the antigen to APCs and stimulate the immune response
-between enterocytes in the mucosa
-especially lining the Peyer patches
-have basal membrane invaginations containing lymphocytes and APCs
Peyer patches
-lymphoid nodule aggregate
-primarly located in the lamina propria or submucosa of the ileum
Brunner glands (duodenal glands)
-typical of the duodenum
-most present in the submucosa but extends also in the mucosa
-compound tubular mucous glands
-empty into the lumen
-secrete mucous (added to the one produced by goblet cells) to protect the intestinal lining and to generate the perfect PH for pancreatic enzymes to work
parts of the large intestine
cecum (ileocecal valve)
ascending, transverse, descending and sigmoid colon
rectum
haustra
large sacs that wrinkle the wall of the colon
tenia coli
the longitudinal smooth muscle in the muscolaris externa of the colon are arranged in 3 longitudinal bands called taenia coli
anal sphincter
at the anus the circular muscle forms the anal sphincter
colonocytes
-primary absorptive cells in the large intestine
-short microvilli
-leaflets of cell membrane indicating active water transport
where are glands in the large intestine?
in the lamina propria
where are glands embedded in the large intestine?
in the lamina propria (rich in MALT)
how many cells do we have in a crypt?
250 cells–>similar number of cells is generated each day
LGR5
marker for stem cells
LGR5 is highly expressed in intestinal crypt stem cells and serves as a key marker for identifying these cells.
where in the GI tract can you find glands in the submucosa?
esophagus and duodenum
where are you if you can see a stratified squamous non keratinized epithelium with a thin layer of muscolaris mucosa?
in the esophagus
