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Kin 1AA3 > Digestive System part 3 > Flashcards

Digestive System part 3 Flashcards

1
Q

what is the absorbable unit of carbs in the small intestine?

A

monosaccharides: glucose, fructose, galactose

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2
Q

what is the absorbable unit of lipids in the small intestine?

A

free fatty acids, glycerol and monoglycerides

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3
Q

what is the absorbable unit of proteins in the small intestine?

A

primarily single amino acids, dipeptides and tripeptides

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4
Q

glucose and galactose absorption in the small intestine

A
  • pass through apical surface by secondary active transport using Na+ conc. gradient
  • glucose and galactose compete for the same protein channel
  • cross basolateral surface by way of facilitated diffusion
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5
Q

fructose absorption in the small intestine

A

passes through apical and basolateral surfaces via facilitated diffusion

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6
Q

amino acid absorption in the small intestine

A
  • pass through apical surface via active transport or secondary active transport with Na+
  • pass through basolateral surface via simple diffusion
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7
Q

dipeptide and tripeptide absorption in the small intestine

A
  • pass through apical surface by way of secondary active transport with H+
  • pass through basolateral surface via simple diffusion
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8
Q

small short chain FAs (10-12C) absorption in the small intestine

A
  • simply diffuse through apical and basolateral surfaces
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9
Q

long chain fatty acids (>12C) and monoglycerides

A
  • bile salts surround long chain FAs and form a micelle which picks up and drops off into other side of apical cell surface by simple diffusion
  • TG are surrounded by chylomicrons (proteins that are too big to enter capillaries) so they enter the lymphatic system through a lacteal of a villus
  • then travel through thoracic duct (central lymphatic vessel) to junction of left internal jugular and subclavian veins
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10
Q

where do absorbed nutrients go once past basolateral surface of intestinal cells? (all nutrients but lipids)

A

they are taken up by a villus blood capillary
to hepatic portal vein
to the liver

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11
Q

fluid ingested/secreted into GI system/day

A

9.3 L

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12
Q

fluid absorbed by GI system/day

A

8.3 L

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13
Q

fluid excreted in feces

A

100ml

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14
Q

large intestine

A

1.5 m long, 6.5 cm wide
4 major regions
ascending and descending colon are retroperitoneal

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15
Q

ileocecal sphincter

A

valve that controls movement of chyme into LI

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16
Q

cecum

A

where SI opens into LI, like a pocket for contents from SI

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17
Q

veriform appendix

A
  • don’t know exact function, contains lymphatic tissue so thought to have some immune function
  • also may aid in microbe formation: repopulation of env’t of colon after a change
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18
Q

4 regions of the colon

A 
from start to end:
ascending
transverse
descending
sigmoid
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19
Q

sigmoid colon

A

S shaped, brings chyme back to midline region of the body

20
Q

right colic flexure

A

located just below liver

ascending colon turns to transverse colon

21
Q

left colic flexure

A

located just below spleen

transverse colon turns to descending colon

22
Q

omental appendices

A

small lipid filled pouches that attach to teniae coli

23
Q

rectum

A

15cm long
thicker muscle layer here than the rest of the GI tract
contains simple columnar epithelium

24
Q

anal canal

A

final 2-3 cm of GI tract
thickened muscle walls form sphincters
contains stratified squamous epithelium for protection

25
Q

internal vs external anal sphincters

A

internal: made of smooth muscle so involuntary
external: skeletal muscle, allows it to be voluntary

26
Q

anal columns

A

folds in mucous membrane of anal canal where arteries and veins are found
- hemorrhoids are a result of swollen, enlarged, or inflamed veins here

27
Q

types of cells found in large intestine (in glands)

A

absorptive cells

goblet cells

28
Q

absorptive cells in LI

A

take up water primarily, some ions, some cells have microvilli surface

29
Q

goblet cells in LI

A

secrete mucous, also help move chyme here

30
Q

muscular layer in LI

A
  • internal circular layer found everywhere

- outer layer of thickened longitudinal muscle found in 3 bands known as the teniae coli

31
Q

teniae coli

A

when it contracts, it forms pockets called haustra

- it’s always slightly contracted

32
Q

gastroileal reflex

A

when stomach is full, gastrin hormone relaxes ileocecal sphincter so small intestine will empty and make room

33
Q

haustral churning

A

hasutrum fills and once distended, contracts to move contents to the next haustrum
– fills cecum and initiates contraction from one haustrum to another

34
Q

peristaltic waves in LI

A

3-12 contractions/min

alternating circular and longitudinal muscle contractions

35
Q

mass peristalsis

A

in LI, strong peristaltic wave from transverse colon (initiated by gastrocolic reflex) pushes contents into rectum

36
Q

gastrocolic reflex

A

when stomach fills, mass peristalsis moves contents of transverse colon into rectum

37
Q

chemical digestion in LI

A
  • no enzymes secreted, only mucous
  • bacteria ferment things
  • bacteria also produce vitamins K and B in colon which get absorbed with water and ions in LI
38
Q

what do bacteria ferment in LI

A
  • undigested carbohydrates produce hydrogen, CO2, methane gases
  • digestion of AAs; indoles and skatoles give odor to feces
  • decomposition of bilirubin to stercobilin which makes feces brown
39
Q

feces

A

produced after 3-10 hours in LI from chyme when 90% of water is reabsorbed
- composed of dead epithelial cells, metabolic byproducts, undigested food (ex. cellulose), bacteria (live and dead; makes up 30% of dry feces weight)

40
Q

defecation reflex

A
  • gastrocolic reflex caused by filling of stomach moves feces into rectum which initiates defecation reflex
  • stretch receptors signal sacral spinal cord
  • parasympathetic nerves contract longitudinal muscles of descending/sigmoid colon, rectum and internal anal sphincters relax
  • external anal sphincter is voluntarily controlled
41
Q

phases of digestion

A

describe regulation of movement through GI system

  1. cephalic phase
  2. gastric phase
  3. intestinal phase
42
Q

cephalic phase

A

preps mouth and stomach for food before or just as our food is eaten: preps mouth and stomach for food, initiated by sight, smell, thought and taste
- neural centres use facial & glossopharyngeal nerves to stim. salivation and vagus nerve to stimulate gastric juice release in stomach

43
Q

gastric phase

A

once bolus reaches stomach causes an increase in both gastric secretion and motility
- receives both neural (feedback loop via parasympathetic and ENS) and hormonal regulation (gastrin), promotes gastric emptying

44
Q

intestinal phase

A

once chyme enters SI, inhibits gastric emptying to promote digestion of our food
- neural (feedback loop: enterogastric reflex) and hormonal regulation (secretions of secretin and cholecystokinin aka CCK)

45
Q

secretin

A

release is stimulated by acidic chyme entering SI

  • stim release of pancreatic juice and decreases gastric secretions
  • all in an effort to reduce acid coming into SI
46
Q

cholecystokinin (CCK)

A

release is stimulated by AA and fat in chyme entering SI

  • stm secretion of pancreatic juice, contraction of gallbladder to release bile and then relaxes hepatopancreatic ampulla so secretions can enter SI
  • decreases gastric emptying by contraction of pyloric sphincter
  • stimulates hypothalamus so the brain has feelings of satiety and we feel full

Kin 1AA3 (11 decks)

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