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z:Physl 210A/B > GIT Lec 6: Small Intestine > Flashcards

GIT Lec 6: Small Intestine Flashcards

(46 cards)

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1
Q

small intestine is between

A

stomach + large intestine

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2
Q

size of small intestine

A
  • tube of 2.4 cm diameter

- 3m length (doubles during autopsy–> loss of tone)

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3
Q

small intestine sections

A

duodenum- 30 cm - close to stomach
jejunum - 1 m
ileum - 1.7 m - close to large intestine

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4
Q

small intestine functions

A

-digestion + absorption of protein, fat, carbohydrates, electrolytes, H2O, minerals, vitamins

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5
Q

functions of duodenum

A
  • mixing pancreatic digestive enzymes + bile with food
  • absorption of nutrients, iron, calcium
  • release of endocrine hormones–> secretin, CCK
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6
Q

functions of jejunum

A
  • digestion + absorption

- most chyme digested + absorbed in first 25% of small intestine

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7
Q

functions of ileum

A

-digestion + absorption (bile acids, vitamin B12)

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8
Q

large SA is important because

A

absorption, exposure to enzymes needs to be increased

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9
Q

folds of small intestine increases

A

SA (epithelial layer)

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10
Q

folds of small intestine (largest to smallest)

A

folds of kerckring –> villi + crypts —> microvilli

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11
Q

type of cells in villus

A
  • stem cells in crypts
  • paneth cells in crypts
  • enterocyte (absorptive) cells -villus stalk
  • goblet cells -villus stalk
  • enteroendocrine cells -villus stalk
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12
Q

paneth cells

A

secrete antibacterial proteins

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13
Q

enterocyte (absorptive) cells

A

absorption , brush-border enzymes

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14
Q

goblet cells

A

secretion of mucus

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15
Q

enteroendocrine cells

A

release of hormones

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16
Q

brush border

A

-small projections (microvilli) at epithelial cells –> major absorptive surface

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17
Q

brush border enzyme

A
  • enzyme anchored to brush border, catalytic activity in lumen
  • breakdown of carbohydrates, pep–> sugars, aa before transport into enterocyte
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18
Q

starch (amylose +amylopectin) products by salivary + pancreatic amylase

A

maltose, maltotriose, a-limit dextrins

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19
Q

enzymes that turn maltose, maltotriose to glucose

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A

maltase
sucrase
a-dextrinase

20
Q

enzymes that turn a-limit dextrins to glucose

21
Q

sucrose enzyme + products

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A
  • sucrase

- glucose + fructose

22
Q

lactose enzyme + products

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A
  • lactase

- glucose + galactose

23
Q

SGLT

Study These Flashcards
A

sodium -glucose linked transporter

24
Q

GLUT2/5

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A

glucose transporter 2/5

25
intestinal absorption of glucose/galactose
apical: glucose/galactose and 2Na+ from lumen into cytosol through SGLT basolateral: glucose/galactose from cytosol into blood through GLUT2 Na+/K+ ATPase-- 3 Na+ out/ 2 K+ in
26
intestinal absorption of fructose
apical: fructose from lumen into cytosol through GLUT5 basolateral: fructose from cytosol into blood through GLUT2
27
lactose intolerance
- all mammals lose some lactase expression - can't completely digest lactose - - decreased water absorption - more water in gut (osmotic gradient into lumen) - bacteria in large intestine digest lactose consequence: pain, diarrhea
28
major pancreatic proteases
trypsin + chymotrypsin
29
further protein digestion (breakdown)
- carboxypeptidase (pancreatic protease) | - aminopeptidase (brush border)
30
protein absorption (apical/basolateral)
apical: free aa coupled with Na+ absorbed (2 active transport) small peptides absorbed by 2 active transport coupled with H+ then peptidases in cytosol: peptides to a.a basolateral: Na+/K+ ATPase, a.a facilitated diffusion across basolateral surface
31
fat absorption
- fatty acids+ monoglycerides processed by ER to make triglycerides= maintains diffusion gradient - aggregate into lipid droplets coated by amphipathic proteins
32
chylomicrons
- extracellular fat droplets - triglycerides, phospholipids, fat soluble vitamins, cholesterol - larger ones enter lymphatic system through lacteals (leakier)- enter systematic circulation through thoraic duct
33
lipoprotein lipase on endothelial cells (blood vessels)
break down of chylomicrons for uptake
34
absorption of iron for the intestine
- Fe2+ actively transported into enterocyte and stored in ferritin protein - not stored: transported into blood + stored in transferrin (plasma protein) - increase iron in body stores --> increase ferritin expression --> decrease absorption of iron - decrease iron i body stores --> decrease ferritin expression --> increase absorption of iron
35
no iron excretion
- iron is toxic | - increase skin pigmentation/heart failure
36
iron deficiency anemia
-decrease number/size in RBC symptoms-tiredness, light-headness, headaches cause: decrease iron /blood loss, poor iron abs. , intestinal disease
37
- Water amount absorbed by small intestine vs feces? | - why water in intestine?
- 8-9 L --> majority absorbed by small intestine -- 100 ml in feces - water in intestine -- permits contact food + enzymes, diffusion of digested nutrients to absorption site, prevents damage to epithelial layer
38
water absorption
determined by Na+ gradients out of cell, apical side | -at villi
39
water secretion
depends on Cl- gradients by 2 active Na+/K+/2Cl- transporter (NKCC1)- basolateral side into cell Cl- (+cAMP) out of cell - apical side increasing cAMP, increasing Cl-
40
Cholera
- ingesting food+water vibrio cholerae bacteria -- produces toxin that increase cAMP, Cl- channel secretion of Cl- into small intestine, increase water in lumen - 20 L of stool causes: vomiting + excessive diarrhea treatment: clean water +electrolytes, intravenous fluids
41
motility (small intestine)- during digestion
- "segmentation" - mechanical breakdown of food, digestive enzymes mixes
42
contractions per min (duodenum)
12
43
contractions per min (ileum)
9
44
motility (small intestine)- after digestion
- segmentation stops, MMC (migrating myoelectric complex) starts - starts lower stomach then 2 feet in small intestine (overlapping waves starts further down - 2hrs then repeat)
45
purpose of MMC
- pushes any undigested material from small to large intestine - removal of bacteria in small intestine
46
Regulation of MMC
- motilin hormone secretion by cells of small intestine -- initiate MMC - feeding inhibits motilin

z:Physl 210A/B (28 decks)

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