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Nutrition > GI (Quiz 1) > Flashcards

GI (Quiz 1) Flashcards

1
Q

What is the role of the GI tract?

A

-extract nutrients
-serve as a physiological barrier to microorganisms & foreign materials

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2
Q

What are the 4 concentric layers of the GI tract (innermost to outer)?

A

-mucosa
-submucosa
-muscularis externa
-adventitia/serosa

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3
Q

Which GI layer has direct contact with food?

A

Mucosa

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4
Q

What does the submucosa contain?

A

-large blood vessels
-lymphatics
-nerves branching into the mucosa and muscularis

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5
Q

What does the muscularis externa consist of? What does it do?

A

Circular inner layer and longitudinal outer muscular layer which are responsible for peristalsis

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6
Q

What does the adventitia/serosa consists of?

A

Several layers of epithelium

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7
Q

What are the Accessory Organs of the GI tract?

A

-pancreas
-liver
-gall bladder

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8
Q

How does the pancreas aid the GI tract?

A

Consists of:
-pancreatic digestive enzymes
-Bicarbonate
-cations (Na, K, Ca)
-anion (Cl)

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9
Q

What is synthesized by hepatocytes?

A

Bile (for fat digestion, emulsifies fat)

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10
Q

What is the function of the gall bladder?

A

Concentrates and stores bile

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11
Q

What is stimulated by CCK?

A

-gallbladder
-pancreatic digestive enzymes

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12
Q

Where is the stomach located?

A

Between the lower esophageal sphincter (LES) and the duodenum (pyloric sphincter)

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13
Q

What is the stomach volume at rest? Expanded?

A

Rest: ~50 mL (2oz)
Expanded: 1.5 L (~37-52oz)

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14
Q

How much gastric fluid can the stomach produce/secrete?

A

~2-3 liters per day

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15
Q

Where does chyme form?

A

The Stomach

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16
Q

Where are parietal and chief cells found?

A

Stomach

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17
Q

What do parietal cells secrete?

A

-hydrochloric acid (HCI)
-intrinsic factor

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18
Q

What do chief cells secrete?

A

Pepsinogen

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19
Q

What is the function of hydrochloric acid and pepsinogen?

A

Denatures ingested proteins

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20
Q

What is the function of intrinsic factor?

A

Aid in B12 absorption

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21
Q

What is secreted by mast cells ?

A

Histamine

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22
Q

What is secreted by g cells?

A

Gastrin

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23
Q

What is secreted by d cells?

A

Somatostatin

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24
Q

What is secreted by mucus cells?

A

Mucus and bicarbonate

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25
Q

What stimulates the production of gastric juice?

A

-hormones (gastrin)
-stomach distention
-thoughts/smell/sight of food
-histamine (binds to H2 receptors on parietal cells)

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26
Q

When does the production of gastric juice stop?

A

When the pH is ~2

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27
Q

Why is there a thick mucus layer in the stomach?

A

To prevent auto digestion

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28
Q

What are the functions of stomach acid (HCl)?

A

-destroys activity of protein
-lowers pH (to ~2)
-partially digests dietary protein
-converts pepsinogen to pepsin
-assists in Ca/Fe absorption by ionizing them

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29
Q

How is the mucosa of the SI different from the rest of the GI?

A

Structured to maximize surface area/absorb more nutrients
Surface area is ~300 m^2

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30
Q

What allows the SI to have an increased surface area?

A

-large folds of mucosa
-villi
-microvilli

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31
Q

What is glycocalyx?

A

-surface coat of microvilli
-most digestion occurs here
—> contains most of the enzymes produced by mucosal cells

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32
Q

Where are bicarbonate ions secreted from?

A

-pancreas
-Brunner’s glands in the proximal duodenum

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33
Q

How long does food stay in the SI?

A

3-10 hours (dependent on composition/amount)

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34
Q

Where are epithelial absorptive cells produced?

A

Crypts (valleys b/w villi)
—> continually undergo mitosis and mature as they move from the crypts to the tips of the villi

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35
Q

What happens to epithelial absorptive cells when they reach the tips of the villi?

A

They are degraded by digestive enzymes and excreted into feces

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36
Q

How often are epithelial absorptive cells replaced?

A

every 3-5 days

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37
Q

What happens to epithelial absorptive cells during nutrient deficiency?

A

They deteriorate
—> if more aren’t made then there will be GI issues

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38
Q

What do goblet cells secrete?

A

Mucus

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39
Q

What is Peristalsis?

A

Contraction of muscularis layer causing chyme to move ahead
-inner circular layer tightens tube
-longitudinal layer pushes chyme forward

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40
Q

What is segmentation?

A

Circular muscle contraction that causes chyme to be broken up/mixed with digestive enzymes

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41
Q

What is pendulum movement

A

Periodic contractions and relaxations of the longitudinal muscles of the intestinal wall

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42
Q

T/F: Segmentation and pendulum movements propel food

A

FALSE

43
Q

What is a cardio spasm?

A

A sustained tight contraction of the muscle sphincter

44
Q

What digestive enzyme is found in the mouth?

A

Salivary amylase

45
Q

Which digestive enzymes are found in the stomach?

A

-pepsin
-lingual lipase (gastric lipase)

46
Q

Which digestive enzymes are found in the pancreas?
(Literally so many)

A

-pancreatic amylase
-trypsin
-chymotrypsin
-carboxypeptidase
-elastase
-co-lipase
-pancreatic lipase
-phospholipase A2
-cholesterolesterase

47
Q

What digestive enzymes are found in the SI?

A

-Aminopeptidase
-enterokinase
-disaccharidase
-> Maltase
-> sucrase
-> lactase
-> trehalase
-> isomaltase

48
Q

Which enzymes digest carbs?

A

-salivary amylase
-pancreatic amylase
-all the disaccharidases

49
Q

Which enzymes digest proteins

A

-pepsin
-trypsin
-chymotrypsin
-carboxypeptidases
-elastase
-enterokinase
-aminopeptidases

50
Q

Which enzymes digest lipids?

A

-lingual/gastric lipase (only in babies)
-co-lipase
-pancreatic lipase
-phospholipase A2
-cholesterolesterase

51
Q

What is bile composed of?

A

-mainly bile salts
-cholesterol
-phospholipids
-bile pigment (direct bilirubin)
-all dissolved in an alkaline solution

52
Q

What are the two primary bile acids?

A

-chenodeoxycholic acid
-cholic acid

53
Q

Where is bile synthesized?

A

Mainly in hepatocytes from cholesterol

54
Q

Where is bile secreted into?

A

the small intestine via common bile duct

55
Q

What does 7 alpha-hydroxylase do?

A

Convert Cholesterol into 7-hydroxycholesterol (adds another OH group to cholesterol)
—> using NADPH + H+

ITS ALSO THE RLE!

56
Q

What is the rate limiting enzyme for bile synthesis?

A

7 alpha-hydroxylase

57
Q

How many hydroxyl groups are in cholic acid? Where are they?

A

3 @ C3, 7, 12

58
Q

How many hydroxyl groups are in chenodeoxycholic acid? Where are they?

A

2 @ C3, 7

59
Q

What is the affect of adding hydroxyl groups to bile salts?

A

More OH = more hydrophilic
—> increases emulsification

60
Q

What is a byproduct of bile acid synthesis?

A

Propionyl-CoA

61
Q

What are the two amino acids that can make conjugated bile acids?

A

Glycine and Taurine

62
Q

What happens when you conjugate a bile acid?

A

Results in improved ionization & ability to form micelles

63
Q

What % of bile acids are conjugated with glycine?

A

75%
The other 25% is taurine:)

64
Q

What are the two conjugated bile acids made by glycine?

A

-Glycoholic acid
-Glycochenodeoxycholic acid

65
Q

What are the two conjugated bile acids made with taurine?

A

-taurocholic acid
-taurochenodeoxycholic acid

66
Q

What makes up a mixed micelle?

A

-bile salts
-triacylglycerol
-pancreatic lipase

67
Q

When is bile sent from the liver to the gallbladder?

A

the inter-digestive period

68
Q

What happens when conjugated bile acids get to the large intestine?

A

Bacteria act —> deconjugation and dihydroxylation

69
Q

What is the secondary bile acid of Cholic acid?

A

Deoxycholic acid

70
Q

The secondary bile acid of chenodeoxycholic acid?

A

Lithocholic acid

71
Q

What is the difference between primary and secondary bile acids?

A

Secondary has no -OH @ C7

72
Q

T/F: 95% of bile acids are reabsorbed by active transport in the ileum and delivered back to the liver

A

TRUE!
Delivered via the portal circulation

73
Q

What is the clinical significance of bile?

A
  1. *** only significant mechanism for eliminating excess cholesterol
  2. Facilitate digesting of triglycerides
  3. Eliminate bilirubin
  4. Facilitate absorption of fat-soluble vitamins/substances
  5. Makes cholesterol soluble in the gallbladder (basically same as 1 but she has both listed)
74
Q

How do gallstones form?

A

when bile becomes supersaturated with cholesterol
—> chol precipitates out —> deposition of Ca, bilirubin, PL to form stone

75
Q

What happens to the gallstones after they form?

A
  1. Resident silently in the gallbladder
  2. Cause cholecystitis (inflammation of gallbladder)
  3. Block the common bile duct
76
Q

What happens at the large intestine?

A

-absorption of 85-90% of water
-Absorption of some minerals/vitamins
-formation of feces

77
Q

What are two examples of facilitated diffusion?

A

-GLUT 5 —> fructose
-GLUT 2 —> glucose + fructose

78
Q

What type of absorption is involved with Na/K

A

Primary active transport

79
Q

What is an example of secondary active transport

A

SGLT —> glucose and Na

80
Q

What are the three main types of absorption

A

-passive
-active
-endocytosis

81
Q

Where does portal circulation occur? What does it carry?

A

-portal vein —> liver
-water-soluble nutrients

82
Q

Where does lymphatic circulation drain? What does it drain?

A

-into left subclavian vein
-fat-soluble nutrients + large particles

83
Q

What is the pathway of bile circulation?

A

Liver—>gallbladder —> SI —> portal vein —> liver

84
Q

What are the regulatory peptides?
(A lot tbh)

A

-gastrin
-cck
-secretin
-gastric inhibitory peptide (GIP)
-glucagon-like peptide (GLP)
-somatostatin
-motilin

85
Q

What stimulates gastrin secretion?

A

-thoughts of food
-food
-distension of the antrum
-peptides and amino acids
-vagus nerve

86
Q

What is the function of gastrin?

A

-stimulates the release of HCl
-stimulates gastric and intestinal motility

87
Q

What inhibits gastrin?

A

-pH less than 1.5
-somatostatin

88
Q

Where is GIP released from?

A

The k cells from duodenum and jejunum

89
Q

What stimulates GIP secretion ?

A

The presence of glucose and fat

90
Q

What is the function of GIP

A

-inhibits gastrin-stimulated gastric acid secretion/motility
Incretin hormone:
-controls blood glucose after a meal
-stimulates insulin secretion

91
Q

Where is cck secreted from?

A

I cells in the duodenum and jejunum

92
Q

What stimulates cck secretion?

A

The presence of fat, peptides, amino acids, HCl

93
Q

What is the function of cck?

A

-stimulates secretion of pancreatic juice/enzymes
-stimulates gallbladder contraction —> release of bile
-inhibits gastrin emptying
-augments the action of secretin

94
Q

What stimulates secretin secretion?

A

The presence of acidic chyme entering the duodenum

95
Q

What is the function of secretin?

A

increase the pH of the duodenum
-increases bicarbonate and water
-decrease gastric acid secretion

96
Q

Where is motilin released?

A

By cells of the proximal SI

97
Q

What stimulates motilin secretion?

A

The presence of bile and pancreatic secretions into the duodenum

98
Q

What is the function of motilin?

A

-increase rate of gastric emptying
-stimulates intestinal motility
-enhances contraction of the smooth muscles

99
Q

Where is GLP released from?

A

Ileal L cells

100
Q

What stimulates GLP?

A

The presences of nutrients in the lumen

101
Q

What is the function of GLP?

A

incretin hormone
-delays CHO absorption
-increase glucose-dependent insulin secretion
-increase pancreatic beta-cell mass
-decrease glucagon secretion
-promotes insulin sensitivity
-inhibits gastric secretion/motility

102
Q

What stimulates the secretion of somatostatin?

A

-Acidic chyme
-products of protein and fat digestion

103
Q

What is the function of somatostatin?

A

-general: inhibitory and anti secretory
—> inhibits gastrin/gip/secretin/motilin
—> inhibits gall bladder contraction

Nutrition (7 decks)

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