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GI 2 Flashcards

Lectures GI 5- GI 6

1
Q

total L of food fluid secretions in intestinal phase

A

5.5L, additional 3.5L from hepatic, pancreatic, and intestinal secretions

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2
Q

how does motility occur in intestinal phase

A

regulated to ensure proper digestion
-combo of segmental and peristaltic contractions to mix chyme w enzymes and expose digested nutrients to mucosal epithelium for absorption

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3
Q

what promotes motility

A

parasymp, gastrin and cholecystokinin (CCK)

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4
Q

what inhibits motility

A

sympathetic

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5
Q

role of villi

A

increase SA for absorption and secrete mucus

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6
Q

what are crypts

A

contain hormone and fluid secretory cells and stem cells

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7
Q

where are most nutrients absorbed

A

capillaries in villi

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8
Q

where do fats enter for transport

A

lacteals of lymph

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9
Q

explain hepatic portal system

A

venous blood from GI tract doesn’t go directly to heart
- liver acts as biological filter, contains lots of enzymes that metab drugs and xenobiotics, clears them before blood proceeds to systemic circulation

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10
Q

5 intestinal secretions for digestion & where

A
  1. digestive enzymes (intestinal epithelium: BBM enzymes and pancreas)
  2. bile (liver, stored in gallbladder)
  3. bicarbonate (pancreas)
  4. Mucus (goblet cell)
  5. isotonic saline (crypt cells), lubricates contents of gut
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11
Q

pancreas contains what endocrine secretion

A

secretory epithelium islets, insulin and glucagon

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12
Q

pancreas contains what exocrine secretion

A

secretory epithelium, digestive enzymes and NaHCO3

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13
Q

pancreas stim for exocrine

A

distension of small intestine, neural signals, CCK

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14
Q

activation of pancreatic zymogens

A

trypsinogen concerted to trypsin by enteropeptidase (BBM enzyme), trypsin then activates zymogens

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15
Q

pancreas produces bicarbonate in what cell and why

A

duct cells to neutralize acid entering from stomach

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16
Q

pancreas bicarbonate secretion exchangers

A

high carbonic anhydrase

  • apical: HCO3-/Cl- exchanger and CFTR channel
  • basolateral: NKCC2, Na/K ATPase, K+, Na/H exchanger

CFTR- cystic fibrosis will alter secretions

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17
Q

3 components of bile

A

1) bile salts (acid/amino acid)
2) bile pigments (bilirubin, biliverdin)
3) cholesterol

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18
Q

bile secreted from…

A

liver- hepatocytes, non-enzymatic

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19
Q

fat digestion, what is, how

A

triglycerides (90%), cholesterol, phospholipids, long chain fa, fat soluble vitamins
-coarse emulsion of fat droplets in chyme broken to smaller stable particles by bile salts

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20
Q

fat absorption

A
  • micelles contact BBM, fa and monoglycerides diffuse into enterocyte
  • cholesterol transported
  • triglycerides reformed in ER and packed w cholesterol into chylomicrons (go to lymph)
21
Q

what are gallstones

A

hardened deposits likely due to excess cholesterol or bilirubin
upper right abdominal pain

22
Q

carb digestion

A

polymers: glycogen, cellulose
disaccharides: lactose, maltose
monosaccharides: glucose and fructose
amylase breaks down polymers to di
di broken down by intestinal BBM enzymes disaccharidases

23
Q

carb absorption

A

glucose or galactose: enter w Na+ on SGLT, exit on GLUT2

fructose: enter GLUT5, exit GLUT2

24
Q

why is glucose not phosphorylated entering enterocytes

A

primarily use glutamine so G6P not formed and free glucose conc stays high to facilitate BLM transport

25
2 protein digestion enzymes
1. endopeptidase, attack peptide bonds forming fragments, pepsin, trypsin, chemotrypsin 2. exopeptidase (aminopeptidase and carboxypeptidase) release single aa from peptides one at a time
26
protein absorption (single and di and tri)
- most single aa on Na cotransporters (apical) and Na exchangers (basol) - di and tri on oligiopeptide transporter (H+ cotransport) - most oligios digested to single aa in cell and exit Na-aa exchanger
27
protein absorption for larger than tri peptides
transported via transcytosis bind to receptor on luminal surface
28
vit and mineral absorption
fat soluble and water soluble iron and Ca+2 exceptions bc regulated B12 absorbed in ileum after forming complex with intrinsic factor released from parietal cells mineral absorption via active transport
29
water and ion absorption
- most water absorbed in small intestine - nutr and ions absorbed make osmotic gradient
30
how is intestinal phase regulated
distension, acid, digestive products in small int, short and long reflexes, endocrine signalling - reduce motility and secretions in stomach, increase in int
31
intestinal motility is primarily regulated by
ENS neurons (myenteric plexus)
32
fed state motility
segmental contractions for mixing and peristaltic cont for forward movement ICC cells: slow waves brought to threshold, distension of stomach and small int, parasymp (long reflex)
33
fasting state motility
Mo cells: secrete motilin- maybe stim by alkaline migrating motor complex (MMC) series of contractions that start at empty stomach and go to large int
34
regulation of endocrine signalling and intestinal regulation
distension, acid, digestive products through short and long reflexes and endocrine signalling - reduce motility and secretions in stomach, increases in intestine - accessory secretions from parasymp - GI peptides (hormones): S- secretin, I- CCK, K- glucose dependent insulinotropic peptide (GIP), L- glucagon0like peptide 1 (GLP-1) these all inhibit gastric secretion and motility
35
pancreatic secretions and int regulation
- begin during cephalic and gastric - gastrin and parasymp - enterohapatic reflex
36
S cells stimulated by and roles
acid entering duodenum from stomach 1. regulate pH - stimulates bicarbonate secretion from pancreas - stim bile from liver 2. inhibit gastric acid secretion - inhibits gastric motility and gastric emptying into small int
37
I cells, stim by.. roles
releases CCK stim by fa and aa in chyme 1. regulates pancreatic enzyme secretion + 2. regulate bile secretion + - inhibits gastric acid production and emptying
38
K cells and L cells - what they release - function
GIP and GLP-1 presence of carb in GI, increase endocrine cells, increase GLP-1 and GIP, Beta pancreas cells, increase insulin, liver stores glucose - glucose homeostasis
39
how are gastric and int phases integrated
enterogastric reflex - neural reflex stim by distension and H+/acid - acid, enzymes, digested food = hyperosmotic chyme = inhibit gastric emptying
40
ileocecal valve
- valve relaxes as contraction proceeds through ileum - food in stomach causes contr of ileum and relaxation of valve (gastroileal reflex)
41
large int secretions
minimal, mucus from goblet cells
42
large int digestion
bacteria digest things - indigestible complex carbs, fats, proteins, broken down and fermented -produce lactate and short chain fa used by colonocytes for energy - produce absorbable vitamins (vit K) - produce gases
43
large int 3 motility
1. slow segmental contractions 2. haustral rolling or churning: thick bands of longtitudinal muscle create pouches called haustra 3. mass peristalsis: gastrocolic reflex- stim by food in stomach 2/3 times/day
44
defecation reflex
1. short reflex: local peristaltic waves 2. long reflex: relax internal sphincter (smooth), contract external, more forceful peristaltic contr from parasymp - completed by voluntary relax external (skeletal) aided by increase abdominal pressure
45
diarrhea caused by
increase in frequency, volume, fluid content of feces due to increase secretion, reduced absorption or increase motility - osmotic, secretory, inflammatory, motility induced
46
clostridium difficile and fecal bacteriotherapy
- use of penicillin based antis can alter normal bacteria flora - remaining bacteria have to compete for space and nutr - leaves body prone to infection by C. defficile - colitis: watery diarrhea, fever, nausea, ab pain - fecal transplant via colonoscopy
47
vomit reflex
medulla and brainstem are vomit centre - primary responses: 1. retrograde cont in small int and stomach 2. cont ab and inspiratory muscles (diaphragm) increase gastric pressure 3. relax esophageal sphincters
48
immune function of GI tract
gut associated lymphoid tissue (GALT)- 80% lymphocytes locates in gut - M cells: immune response: receptor mediated endocytosis, bind to antigens/foreign peptides - transport antigens to macrophages, lymphocytes, dendrites - release cytokines to attract more immune cell to attack invaders - cytokines can also trigger increased Cl- secretion (diarrhea) to flush pathogens

BMSC 208 (8 decks)

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