digestive system III and IV Flashcards
name layers of general plan of digestive system
mucosa
submucosa
muscularis
serosa
describe mucosa of general plan
epi = continous with oral cavity, nonkeratinized strat squa epi
lp = loose ct
muscularis mucosae = separates mucosa from submucosa, muscle tissue, most developed in esophagus- see fibers
describe submucosa of general plan
loose or dense ct
describe muscularis of general plan
2 sublayers = internal circular and external longitudinal *smooth muscle nuclei, different sections
3 sublayers in stomach
describe serosa of general plan
called adventitia untill diaphragm
why does digestive system look wavy
due to fixation
describe submucosal glands
has many glands
esophageal/mucous
mucous glands called esophageal glands - lubrication for food stuff to slide down easier
describe esophageal glands
have duct that runs up through submucosa, muscularis mucosae and to lumen to release mucous in esophagus
describe the stomach
dilated segment of digestive tract
main action is to add an acidic fluid - pH 2 - to ingested food to transform it into a viscous mass called chyme
Secretes intrinsic factor - essential to absorb vitamin b12
produces hormones like gastrin - hormone for digestion
describe stomach mucosa
described as pits or glands = invaginations all along stomach - to increase SA - amount of space for cells to come into contact with food stuff- to breakdown
describe stomach epithelium
simple columnar
rest on bm
describe when esophagus empties into stomach
cardia - 1cm tiny area
fundus
body - gastic region, rest of stomach
Pyloric region = stomach ends, empties into duodenum of si
describe muscularis of stomach
3 layers
outer longitudinal
inner circular
Oblique layer - force to mix contents of stomach
makes food stuff acidic = chyme
describe stomach submucosa and serosa
dense and loose ct
not thin
serosa= connects stomach to visceral peritoneum
describe pits and glands
pits = cells very different from glands, closer to lumen
Glands = base of lumen
describe tight junctions - story of stomach
people used to think that tight junctions would erode - degrade and leak stomach acid - causes ulcers
but actually caused by helio bacter pylori
90% of ulcers can be cured by antibiotics
grad student took bacteria and got ulcers and took antibiotics and got better
name ratios for each region of stomach and why
cardia =1:1
pyloric = 2:1
gastric = 1:3
ratio based on length/size, guestimation
what is neck region
around where pit turns to gland
describe surface mucous cell
very important
carbohydrate rich, glycoproteins, describes as visible mucous - due to cloudy appearance
forms a thick viscous gel like coat, mucous super dense and thick, adheres to epithelial surface
high bicarbonate concentration = local buffering
columnar cells
most apical - makes mucous and protects stomach from stomach acid - neutralizes stomach acid at layer of mucosa
tight junctions, desmosomes, mucous granules - carb rich, glycoproetins, rests on bm
mitochondria, nucleus
electron dense
describe mucous neck cells
mucous much more soluble - protection
not as viscous or thick
want things to be able. to travel from base of gland to lumen
funnny shape
tight junctions on either side
secretory granules, central nuclei
stil protects from acidic environment of stomach
describe zymogenic - chief/peptic cells
tight junctions, bm, central nuclei, lots of er and golgi
Makes hormones or digestive enzymes = secretory granules
converts pepsinogen –> pepsin, breaksdown amino acid bond
makes enzymes to breakdown foot and fat- lipase
releases secretory granules into lumen of gland portion of epithelium
further breakdown in stomach or si - also these cells in si
describe argentaffin - enteroendocrine cells
argentaffin bc stain silver
argentaffin granules = gastrin, serotonin, histamine, VIP, glucagon and somatostatin
funky cell
Hard to see in h&E stain
central nuclei - rests on bm
makes hormones responsible for digestive tract
does not release contents into lumen but through bm into digestive tract
describe parietal - oxyntic cells
base of gland has many
looks like fried egg
have HCl
tight junctions, rests on bm
canaliculi - run through and have microvili = increase surface area of cell
describe intrinsic factor
if none = problem making blood
vitamin b12
pernicious anemia
what are atrophic gastritis
antibodies attack parietal cells and no intrinsic factor and b12 absorption = leads to pernicious anemia
describe carbonic anhydrase
Parietal cells make hcl that make stomach acid
need carbonic anhydrase to make HCl
enzymes catalyses reaction
carbon dioxide plus water –> carbonic anhydrase (enzyme) –> bicarbonate .. makes HCL
describe SI - pathway
stomach empties to duodenum = c shaped tube, 30cm, common bile duct dumps contents into start of duodenum
jejunum - 12 feet
ileum - comes around into LI (colon)
describe small intestine functions
further digestion of partially digested macromolecules - largely by pancreatic enzymes
terminal digestion of proteins, carbs, occurs at mucosal surface by enzymes of intestinal orgin and resulting aas, monosaccarides, fatty acids, monoglycerides are absorbed along si
duodenum, jejunum, ileum - morphological difference at level of submucosa
start to absorb food here
what is last part of digestion
common bile duct in duodenum and pancreatic enzymes = last part of digestion happens
describe duodenum
villi - top and crypts - down
crypts of lieberkuhn
increases SA = want to extract stuff from chyme and want cells to come in contact with it
brunners glands
describe brunners glands
secretes an alkaline fluid - pH 9, rich in bicarbonate
Neutralizes stomach acid at that site
released into crypts
common bile duct = because pancreatic enzymes work at neutral pH
describe jejunum
eruptions of submucosa push into mucosa
plicae circularis - valve of kerking, eruptions of mucosa
increases surface area = contact with food stuff
need invaginations = crypts and villi
pushes villi up
lined by simple columnar
describe ileum
basic plan, nothing special
describe plicae circularis
extend around one half /two thirds of circumference of lumen of si
well developed in jejunum
increases surface area of mucosa by 3
describe transition between stomach and si
pits change to villi and glands are now submucosal - brunners
describe paneth cells
base of crypts
release lysozymes, and breakdown bacteria cell wall through Bm
LOTS OF mitosis - many mitotic sections base of crypt - villi, cells divide a lot
describe enteroendocrine cells
release hormones down under bm
through bm
regulates digestion further away - not in lumen
describe goblet cells
tons
makes mucous
lubricate and protection - like things getting stuck
describe columnar cells with striated border
brushborder
looks like brush
cells sloughing off
after 3-4 days
at top of vili
describe lamina propria of si
loose or dense ct
innervation and blood supply - vessels, used to take absorbed nutrients to other parts of body
lymphatics
smooth muscle = contraction causes villi to move and mix food
where are stem cells located in si
base of crypts - can divide or differentiate
much turnover in si
digestive tract ~3days
name parts of si mucosa - general plan
villi - simple columnar
crypts - simple columnar
lamina propria
muscularis mucosae
explain villi of mucosa of si
columnar cell with brush border = absorptive cell, enterocytes
goblet cells
M cells - microfold cells, peyers patches and galt
describe enterocytes - meaning
things entering through cells
describe GALT/peyers patches
gut associated lymphatic tissue
introduces pathogens and allows body to make antibodies to it
explain crypts of mucosa of si
Columnar cell with brush border - absorptive cell
goblet cell
enteroendocrine cells - secrete cck
paneth cell - lysozyme
stem cell
what is cck
cholecystokinin
contraction of gall bladder and pancreatic secretion
hormone made in duodenum = enteroendocrine cells, passed through bm and goes to gallbladder, = squeezes bile to pancrease to release enzymes for digestion
where is food absorbed in si
enterocytes
describe enterocytes
brushborder on top of cell = microvilli - increase sa
tight junctions stick cells together
under tj = zonula adherens and below= desmosomes
describe components of enterocytes
dense matrix - villin, actin myosin - terminal web
glycoproteins
dissacharides
dipeptidases
alkaline phosphatase
enterokinase - duodenum = trypsinogen to trypsin- breaks down aas - peptide bonds
describe microvilli of enterocytes
made of actin - links to actin - actin terminal web
actin bundled villin - links actin bundles to pm
underneath = myosin = terminal web
myosin contracts = makes villi move and mixes more
what enzymes breakdown food stuff
many enzymes
end with ases - into smallest components
describe chylomicrons
monoglycerides, cholesterol, fatty acids, phospholipids, oils – non aq, want to push through PM - to blood supply = endocytosis and bring to golgi = meets apolipoprotiein - made in rer = chylomicrons
makes its more water soluble and travels through blood to liver where fats are metabolized
hydrophobic inside and hydrophilic outside
describe role of si in IgG absorption
igg molecules = passive immunity
enterocytes have receptors for these
plasma cells can make antibodies - igas
digestive tract can see what is non self
what do M cells do
hey something is foreign
takes bacteria and talks through lymphocyte
M cells turn lymphocytes into plasma cells - to make antibodies
Specialized absorptive cells
huge inflammation process
what are lymphocytes looking for
bacteria
describe large intestine - parts
si feeds into back of li
cecum - blind pouch, bottom of li
vermiform appendix
ascending, transverse and descending colon
sigmoid colon and rectum
are there villi in large intestine
noooo just CRYPTS
describe tunica muscularis of large intestine
3 layers
inner circular
longitudinal = bundles into 3 rd thick muscle layer = contracts more force
outer longitudinal = teniae coli
name 4 cell types of large intestine
goblet cell
absorptive cell
enteroendocrine cell
stem cells
describe goblet cells of large intestine
many goblet cells to lubricate colon - thick since everything being absorbed out so need mucous
usually colon cancer starts at level of goblet cells going bad
describe absorptive cells of large intestine
take up water and salts
describe enteroendocrine cells of large intestine
regulate movement of colon = squeeze
describe stem cells of large intestine
stem cells at bottom of crypt = divide or differentiate into cell types above
