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Practice Topics Exam 5 > GI Physiology 6 > Flashcards

GI Physiology 6 Flashcards

1
Q

Summary of nutrient absorption sites - Primary site is the

A

Small intestine

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2
Q

Summary of nutrient absorption sites - __ of the small intestine impacts the efficiency of absorption

A

Surface area!

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3
Q

What impacts the sites of absorption throughout the small intestine

A

Distribution of enzymes and transporters

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4
Q

SA of the SI

A

Is very large - the villi allow for such a large SA of the SI (no villi with LI)
If you damage the villi, you dramatically change SA and impact abs capacity

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5
Q

Digestion of carbs - Our intestine is only set up for

A

Monosaccharides!

So you have to digest poly and oligosaccharies to the mono in order for it to be absorbed

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6
Q

Digestion of carbs - First primary site of carb digestion is

A

In the lumen of the intestine

Mediated by alpha amylase which comes from the pancreas (pancreas secretion is stimulated by CCK)

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7
Q

Digestion of carbs - Complete the digestion of carbs

A

At the brush border

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8
Q

Absorption of carbs - Digestion of carbs - Important regulatory proteins

A

SGLT1
GLUT5
GLUT 2

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9
Q

Digestion of carbs - SGLT1

A

Nutrient sodium coupled transporter (or the Na glucose transporter)

Moves glucose and galactose across the apical membrane with Na

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10
Q

Digestion of carbs - GLUT5

A

Channel that allows for uptake of fructose

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11
Q

Key to Digestion of carbs

A

You have to break down saccharides into monosaccharides and this is happening in the duodenum and jejunum

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12
Q

Digestion of protein -

A

Pretty sufficient
At any stage you can absorb protein
Protein digestion begins in stomach with pepsin enzyme (which comes from chief cells)

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13
Q

Digestion of protein - once you have oligopeptides and amino acids - empties from stomach into

A

Into duodenum and then you have trypsin enzyme (coming from the pancreas) activated in the duodenum to trypsinogen

CCK is primary stimulus for trypsinogen secretion

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14
Q

Digestion and absorption of protein - Amino acids can be absorbed

A

across the apical membrane and takes place throughout all sections of the intestine

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15
Q

Digestion and absorption of protein - The amino acids are absorbed by

A

Transporters (referred to as nutrient sodium coupled transporters) and they are highly functional during the fed state

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16
Q

Digestion and absorption of protein compared to carbs

A

Proteins - you do not have to break them down into amino acids - you can take the oligopeptides
Carbs - have to be monosachharides

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17
Q

Digestion and absorption of protein - Oligopeptides are transported across the membrane by

A

H linked cotransportes (or H oligopeptide cotransporters) such as PEPT1

The intracellular oligopeptides are further digested into amino acids by intracellular peptidases

And then can be transported across membrane into the blood

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18
Q

Lipid digestion and emulsification - Lipids primarily come in your diet in the form of

A

Triglycerides

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19
Q

Lipid digestion and emulsification - In the lumen of the stomach you have

A

Physical/mechanical disruption called emulsification of the fat
There is not a chemical change of fat in the stomach - just physically disrupting it

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20
Q

Lipid digestion and emulsification - The more fatty the meal,

A

The longer it is in the stomach

You want to physically disrupt it to get it as small as possible

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21
Q

Lipid digestion and emulsification - After emulsification in the lumen of the stomach

A

In the duodenum you start mixing with pancreatic lipase and co lipase

And then mix with bile and facilitate absorption

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22
Q

Lipid digestion and emulsification - For fat absorption we want to stimulate what organ

A

the pancreas because that is where the lipase will come from

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23
Q

Lipid digestion and emulsification Compared to carb and protein

A

With carb and protein - there is no role for the liver

With fat - we need the bile, so there is a role for the liver

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24
Q

Lipid emulsification

A

water and fat do not mix well - so bile acids serve as an emulsifying agent

We will inc water solubility of our fat by mixing the digestive fat with the bile and bile will help emulsify it until you end up with a micelle - micelle can move through aqueous environment toward surface of enterocyte

Change in pH at surface causes micelle to fall apart and then you can have active and passive transport of your fats

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25
Q

Delivery of lipid products to enterocytes by micelles - in the absence of bile

A

Your absorption is less efficient and you are not delivering as much fat to surface of enterocyte

26
Q

Delivery of lipid products to enterocytes by micelles - If you have impairments in bile production - nutritionally, that will show up as what

A

Deficiency in fat soluble vitamins (a, d, e, k)

27
Q

Delivery of lipid products to enterocytes by micelles - once across the membrane what happens

A

You repackage the fat and package it with lipoproteins to form a chylomicron
Chylomicron taken up into lymph and then gets into circulation

28
Q

Delivery of lipid products to enterocytes by micelles - After you absorb the fat into the enterocyte, you

A

repackage it as a chylomicron and that is what shows up in circulation

29
Q

Intrinsic factor - important for

A

very important for vit B12 absorption (need to be bound together for vit B12 to be seen)

30
Q

Vit B12 absoprtion - Vit B12 in complex with IF will move from __ to ___

A

From the small intestine to the ilium

31
Q

Vit B12 absoprtion - Ileum

A

Ileum expresses IF receptor

IF receptor sees the IF (not vit B12)

32
Q

Two ways to cause a vit B12 deficiency

A

1 death to parietal cells, atrophy of gastric mucosa (will not secrete IF)

2 damage to the ileum (won’t have the IF receptors)

33
Q

So if someone is presenting with pernicious anemia could be issue with

A

stomach or the ileum

34
Q

Intestinal absorption of iron - Iron is taken up by the

A

Duodenal enterocytes

35
Q

Intestinal absorption of iron - what do you need

A

Vitamin C to convert the iron into an absorbable form

36
Q

Intestinal absorption of iron - Different ways for Iron to be absorbed

A

Can be taken up when associated with heme (endocytic process)

Can be taken up by transferrin receptor

Can be taken up by divalent cation transporter 1 (DCT1)

37
Q

Calcium absorption

A

In duodenum through a Ca channel

Expression of Ca channel is regulated by vitamin D (which is a fat soluble vitamin)

So if you have impairments in fat soluble abs, you can also have impairments in Ca absorp

38
Q

Lactose intolerance is what type of disorder

A

Absorption

39
Q

Lactose intolerance - lactase is expressed

A

At the brush border
It will take lactose and covert it to glucose and galactose and then those are taken up by SGLT1

Lactose intolerance - you are not expressing the lactase enzyme anymore, so you cannot convert lactose to glucose and galactose (and we can’t absorb these - need to be monosaccharides)

40
Q

Lactose intolerance - What is the result of lacking lactase enzyme

A

you get an accumulation of lactose in the lumen

41
Q

Lactose intolerance - what happens from having an accumulation of lactose in the lumen?

A

Osmotic pressure changes and you retain water in the lumen

intestinal bacteria will rbeak down the lactose and this will release CO2 and hydrogen gas - leading to bloating and distention that is painful

42
Q

Celiac sprue is what kind of disorder

A

Absorption

43
Q

Celiac sprue - AKA

A

Gluten sensitive enteropathy

44
Q

Celiac sprue - is what

A

immune reaction to protein component of cereal grains

- results in malabsorption and inflammation

45
Q

Celiac sprue - what happens

A

GLuten stimulates an immune response at the mucosal surface so enterocyte takes up the gluten and you have a change in those cells and they start to act like antigen presenting cells

System thinks something is wrong and attacks and kills the enterocytes

46
Q

Celiac sprue - What happens over time with repeated exposure

A

You damage and lose the villi so you have dec absorption deficiency of everything

47
Q

Intestinal transport of fluid and electrolytes - in the small intestine there is a net absorption of ___ and a net secretion of ___

A

Na, K, Cl
and a net secretion of HCO3

Uptake salt and secrete bicarb

48
Q

Intestinal transport of fluid and electrolytes - in the large intestine

A

Still net abs of Nacl

But now you secrete K and Bicarb

49
Q

Intestinal transport of fluid and electrolytes - What is impacting how the electrolytes are being handled by the enterocytes

A

Immune system, Enteric nervous system and the endocrine system

SA is important too

Motility is important too - Short transit time - dec amount of abs

50
Q

Intestinal transport of fluid and electrolytes - In general there is a net ___ of water in the GI tract

A

Absorption
NaCl absorbed through the villus and water follows
But you can also secrete fluid by regulating Cl
(done within the crypts)

Generally net abs
Regulate abs by uptake Na
Regulate secretion by secreting Cl ions

51
Q

Intestinal transport of fluid and electrolytes - in disease state - If we dec the salt uptake

A

You stimulate Cl secretion and now fluid moves into the lumen

Generally still see regular nutrient absorption

52
Q

Regulation of intestinal ion/fluid transport - what will lead to more fluid secretion??

A 
Active immune system
Endocrine regulators (histamines, prostaglandins)
Enteric NS (VIP, Ach, 5HT)
53
Q

Regulation of intestinal ion/fluid transport - Motility and SA

A

Have a huge impact

Opiods for example will slow motility and lead to longer time for abs

If you reduce SA, you dec time for abs

54
Q

S/S of GI pathophys - Define diarrhea

A

Inc in the number of bowel movements or a decrease in stool consistency

55
Q

S/S of GI pathophys - Diarrhea can be caused by

A

Inc intestinal secretion
Dec intestinal absorption
Increased osmotic load
Abnormal intestinal mobility

56
Q

S/S of GI pathophys - Osmotic diarrhea is what

A

Diarrhea caused by a non absorbable nutrient

Retention of fluid (can’t absorb it)

57
Q

S/S of GI pathophys - Secretory diarrhea is what

A

Diarrhea caused by intestinal secretion of fluid and electrolytes

Secretion of fluid

58
Q

S/S of GI pathophys - Osmotic diarrhea causes

A

Disaccharide deficiency (like lactose intolerance)

Pancreatic enzyme deficiency
Nutrient binging substances
Loss of enterocytes
Bacterial overgrowth
Antacids
59
Q

S/S of GI pathophys - Secretory causes

A

Enterotoxins
Inflammatory cytokines
Tumor

60
Q

S/S of GI pathophys - If both (secretory and osmotic) at same time, can be caused by

A

Inflammtory conditions

Infectious disease

61
Q

S/S of GI pathophys - Constipation is what

A

Infrequent or difficult evacuation of the feces

62
Q

S/S of GI pathophys - Constipation causes can be

A

Diet/lifestyle (fiber for ex, fluid intake)
GI (stricture, hernia, adhesions, CA, inflammation)
Pharmacological
Endocrine
Neurogenic

Practice Topics Exam 5 (13 decks)

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