Feb14 M1-Histo lecture 2 Flashcards
dx tool to distinguish the duodenum
Brunner’s glands (mucous glands) in the submucosa
dx tool to distinguish the jejunum
submucosa of dense CT (but no glands) pushes mucosa to make permanent plicae circularis (or valves of Kerkring)
ileum appearance on histo
plicae circularis get shorter and disappear
charact of SI mucosa
villi with small crypts at their base called crypts of Lieberkuhn (openings looking like circles on histo)
where’s the LP in SI mucosa + its characteristics
is loose CT (very cellular) fills the space under villi and between the crypts
Brunner’s gland fct in the duodenum
open near the crypts and make mucin that is rich in bicarb to neutralize acidic chyme from stomach
charact of serosa in the jejunum
infiltrated by fat tissue
rugae of the stomach vs plicae circularis of the jejunum
rugae disappear when stomach dilated
plicae circularis never disappear but simply pushed against the wall of the intestine
main concept in distinguishing the 3 parts of the SI
submucosa (Brunner’s or plicae or dimishing plicae)
SURFACE epithelium composition in the small intestine
simple columnar epithelium: absorptive enterocytes with striated border + mucus-secreting goblet cells
where are the stem cells in the small intestine (stomach = isthmus) + what they can do
in the crypts. can divide to make committed cells and then these committed cells (ex enterocytes) can divide outside of the crypts to make more cells like them
goblet cells charact
big, bulky, pale, mucous secreting
absorptive enterocytes charact
simple columnar epithelium, more abundant, brush border, nucleus at the basal side. cover the intestinal crypts
important charact of intestinal mucosa
form villi with lymphatics and blood capillaries inside them (in LP in middle of the villus)
turnover rate of intestinal mucosa epith and meaning
45 days. time needed for cells to migrate from base of crypt to top of villus and get sloughed off
clinical importance of turnover rate of intestinal epithelium
ANY cancer treatment of ANY cancer affects stem cells of gastric and intestinal mucosa and will get bleeding eventually
what allows motion of the villi in the SI
muscularis mucosa (SM)
name of lymphatics in villi and what are they made of
lacteals (lymphatic ‘‘capillaries’’): endothelial layer of squamous simple epithelium
intestinal stem cells on histology
pale cells at the base of the crypts, between the paneth cells
paneth cells charact and what creates them
(made by stem cells). zymogenic and have granules. make lysozymes to destroy bacterial walls + regulate intestinal flora
other cell type in middle of SI crypts + fct
enteroendocrine cells. face BM, like in stomach, and screte contents in LP
phenomenon observed in SI crypts
lot of mitosis (for future goblet cells or enterocytes)
how cell migration to lumen occurs in SI mucosa and what cells
all except Paneth cells. mature as they go to the lumen and push each other
3 cell types in villi (simple columnar epithelium)
- columnar cells with brush border (absorptive enterocytes)
- goblet cells
- M cells (microfold cells)
M cells function
associated (are near) with Peyer’s patches (GALT: gut associated lymphatic tissue)
5 cell types in the SI mucosa crypts (simple columnar epithelium)
- absorptive enterocytes (columnar with brush border)
- goblet cells
- enteroendocrine cells
- paneth cells (lysozymes)
- stem cells
important hormone released by SI crypts enteroendocrine cells + fct
CKK (cholecystokinin): contraction of gallbladder + promotes pancreatic secretions
villi in duodenum (why different from rest of intestine
tortuous and a lot of rotations
why jejunum has an even higher surface area for absorption
plicae circularis 1st level and then villi 2nd level
Peyer’s patch def + location in duodenum vs ileum and colon vs appendix
concentration of lymphocytes, mainly T lymphocytes.
duod: are in LP
ileum and colon: are in submucosa
appendix: in submucosa but penetrate LP
Paneth cells location and how to distinguish them
in intestinal crypts. granulated, nucleus at the base, foamy cytoplasm
absorptive cells (enterocytes) on EM
striated border formed by microvilli
microvilli what’s inside and what’s at their surface
inside: core of actin filaments
on surface: glycocalyx: glycoprotein coat
4 important proteins in glycoprotein coat and what they do
- enterokinase IN DUODENUM activates enzymes from pancreas
- disaccharidases
- dipeptidases
- alkaline phosphatase (dissolve ether phosphate)
why microvilli can have some contraction happening in them
actin filaments + bit of myosin
2 elements for lipids (TGs) digestion + breakdown products
- bile acids from the liver (to emulsify) + lipases from the pancreas.
- gives glycerol, FAs and monoglycerides
how lipid breakdown products handled in SI
enterocytes absorb, reassemble TGs in smooth ER, join to apoproteins to make and secrete chylomicrons that go to the liver
how chylomicrons reach the liver (they circulate where)
go to lymph (lacteals), capillaries and portal veins too
2 important pancreatic enzymes and what activates them
trypsinogen (trypsin) and pro-carboxypeptidase (carboxypeptidase).
activated by enterokinase
M cells location and shape
in intestinal villi between between enterocytes. have infolding on basal side to accomodate for lymphocytes of GALT (gut associated lymphoid tissue) = Peyer’s patch
how M cells work with GALT
internalize antigens and expose them on basal surface to T lymphocytes. stimulate prod of IgAs mainly and IgG too
goblet cell on EM
mucous in apical cytoplasm + on surface to lubricate and protect intestinal surface (creates mucous coat)
charact of epithelium in large intestine
no villi, crypts only. simple columnar epithelium
where’s LP in LI
occupies space between
muscularis mucosa in esophagus vs intestine and colon
esophagus: is longitudinal (along tube axis)
intestine and colon: circular
5 cell types in colonal epithelium
- absorptive cells
- goblet cells
- entero-endocrine cells
- stem cells
(5. Paneth cells ONLY at level of hepatic flexure)
where are paneth cells in colon
hepatic flexure only
submucosa charact in colon
loose and dense CT
tunica muscularis charact in colon
forms bands of concentrated SM running along tube axis at specific places: tenia coli
appendix connects to what portion of GI tract
cecum
appendix epithelium charact
crypts like rest of LI but less abundant (simple columnar epith)
GALT (lymphatic nodules) present where in the appendix
submucosa and disrupt muscularis mucosa and penetrate into the LP
submucosa charact in appendix
infiltrated with fat
tunica muscularis in appendix
inner circular and outer longitudinal
complication of appendicitis
rupture of appendix wall and peritonitis
why colitis and diarrhea are very bad
diseases of absorption of water (and lot of water put out in GI tube and reabsorbed) so lose a lot of water
malignant tumors of the large bowel are mostly what cancers + epi stat
adenocarcinomas. 2nd most common cause of cancer death in North America.
