GI Small Intestine

Question 1

SI section lengths

Answer 1

duodenum: 25 cm
jejunum: 2.5 m
ileum: 3.5 m

Question 2

plicae circulares

Answer 2

transverse folds

mucosa + submucosa

Question 3

villi

Answer 3

independently contractile extensions of mucosa into lumen

made of many cells

Question 4

microvilli

Answer 4

extensions present on one cell

Question 5

glycocalyx

Answer 5

network of polysaccharides

Question 6

glycocalyx fxn

Answer 6

aid digestion
dipeptidase and others break down sugars and protein
viscosity makes barrier to larger

Question 7

reason for SI velvety appearance

Answer 7

villi

Question 8

lacteal location

Answer 8

LP of SI

Question 9

lacteal structure

Answer 9

blind-ending lymphatic capillary
runs through LP of each villi
milky

Question 10

lacteal fxn

Answer 10

collects dietary fat and lymph

Question 11

how to drain lacteals

Answer 11

SM fibers from MM help

Question 12

immune system in SI

Answer 12

lymphocytes
plasma cells
eosinophils
macs
peyer's patches

Question 13

peyer’s patches

Answer 13

nodular aggregations

Question 14

crypts of lieberkuhn structure

Answer 14

go from MM through LP to lumen
simple tubular glands (simple columnar epi)
in SI theyre between villi

Question 15

MM in SI

Answer 15

2 thin layers of SM

Question 16

crypts of lieberkuhn fxn

Answer 16

secrete enzymes for digestion

ex: sucrase

Question 17

SI epithelial cell types

Answer 17

enterocytes
goblet cells
paneth cells
enteroendocrine cells
M cells

Question 18

enterocyte structure

Answer 18

tall
basally located, oblong nuclei
microvilli w/ actin core
terminal web contraction to up absorption
lots of mito, golgi sER and rER
joined by junctional complexes - tight barrier

Question 19

enterocyte fxn

Answer 19

transport things from lumen to circulatory
secrete H20, electrolytes, enzymes for digestion
keep chyme liquid

Question 20

selective retention - mech

Answer 20

tight jxns @ apical
lateral interdigitations
movement of water and solvents into cell, then pump Na (and water) into intercellular space (solvent drag)
P builds - push into caps

Question 21

c. perfringens mech

Answer 21

exotoxins (12+) produce gaps in plasma membrane, inhibit ZOs
intercellular seal is disrupted
interstitial fluid leaks into lumen

Question 22

c. perfringens Sx

Answer 22

cramping, nausea, diarrhea

Question 23

c. perfringens Tx

Answer 23

self-limiting (fluids given)

Question 24

goblet cell structure

Answer 24

unicellular gland
nucleus @ basal end
large golgi
stain lightly (mucous lost in prep)

Question 25

goblet cell fxn

Answer 25

produce mucous lubrication protection

Question 26

goblet cell location (SI)

Answer 26

increase in # from duodenum to ileum

Question 27

paneth cell structure

Answer 27

basophilic basal cytoplasm | eosinophilic granules face lumen

Question 28

paneth cell location

Answer 28

base of blands in SI

Question 29

paneth cell fxn

Answer 29

secrete antibacterial lysozyme and alpha-defensiins phagocytize regulate norm bacterial flora

Question 30

enteroendocrine cell structure

Answer 30

nucleus @ lumen end | granules @ basement membrane

Question 31

enteroendocrine cell fxn

Answer 31

synth peptide hormones (CCK, secretin, GIP, motilin) synth paracrine hormones (SS, histamine) synth neurocrine hormones (VIP, bombesin, enkephalins)

Question 32

M cells structure

Answer 32

have microfolds (M) not microvilli

Question 33

M cell location

Answer 33

interspersed w/ enterocytes | covering peyer's patches

Question 34

M cell fxn

Answer 34

endocytic | transport Ag to epi intercellular space to stimulate immune response

Question 35

plasma cell SI actions

Answer 35

release IgA --> bind to receptor on basal side of enterocyte endocytosed and brought to lumen

Question 36

eosinophil SI actions

Answer 36

phagocytize Ag and Ab complexes | release histammine to generate more response

Question 37

brunner's glands location

Answer 37

``` duodenum submucosa (under MM) ```

Question 38

brunner's glands fxn

Answer 38

secrete zymogen and mucous | basic, 8.2-9.3, counterbalance acidic chyme

Question 39

brunner's glands structure

Answer 39

branch tubular | columnar cells of ducts

Question 40

muscularis externa contractions

Answer 40

segmentation: move contents locally (mix - circular layer) peristalsis: move contents distally (longitudinal)