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Patho 2 > 2 - Gastrointestinal 02 > Flashcards

2 - Gastrointestinal 02 Flashcards

1
Q

What causes acute pancreatitis?

A

Pancreatic secretions build up in the pancreas and overwhelm the effects of trypsin inhibitor

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2
Q

Where is pancreatic bicarb secreted?

A

Mainly in the epithelial cells in the ductules and ducts leading from the acini

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3
Q

What are the basic stimuli for pancreatic secretion?

A
  1. Acetylcholine
  2. Cholecystokinin (CCK)
  3. Secretin
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4
Q

Describe the cephalic phase of pancreatic secretion

A

acetylcholine released by the vagus causes moderate amounts of secretion (20%) into the acini

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5
Q

Describe the gastric phase of pancreatic secretion

A

nervous stimuli accounts for 5-10% of secretion

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6
Q

During what phase does pancreatic secretion become copious?

A

Intestinal Phase

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7
Q

________ stimulates copious secretion of bicarb ions, which neutralizes acidic stomach chyme in the intestines

A

secretin

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8
Q

Describe the intestinal phase of pancreatic secretion

A

Acid from the stomach releases secretin from the wall o fthe duodenum

Fats and amino acids from the duodenum release CCK

Secretin and CCK are absorbed in the blood

secretion causes copious secretion of pancreatic fluid and bicarb

CCK causes secretion of enzymes

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9
Q

How much bile does the liver secrete each day?

A

600-1000 ml/day

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10
Q

Bile serves two functions:

A
  • Fat digestion*: Bile acids emulsify large fat particles and aid in absorption of digested fat through the mucosal membrane
  • Excretion*: Bile serves as a means of excretion of bilirubin and excess cholesterol (among many other things)
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11
Q

What is the purpose of the gallbladder?

A

stores and concentrates bile

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12
Q

By far the most abundant substances secreted in the bile are:

A

bile salts

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13
Q

What substance stimulates gallbladder emptying?

A

CCK

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14
Q

gallbladder emptying requires relaxation of the _______

A

sphincter of oddi

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15
Q

The precursor of the bile salt is:

A

cholesterol

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16
Q

Without the presence of bile salts, what would happen?

A

40% of ingested fats would be lost into the feces

often leads to a metabolic deficit

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17
Q

What percentage of bile salts used in the intestines are reabsorbed into the blood?

A

95%!

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18
Q

Why does chronic inflammation of the gallbladder lead to gallstones?

A

Changes the absorptive characteristics of the GB mucosa

Allows excessive absorption of water and bile salts, but leaves behind cholesterol

Cholesterol gets more and more concentrated

Begins to precipitate and form crystal, which progress to gallstones

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19
Q

Secretion of mucus into the small intestine is acheived by _______ glands

A

Brunner’s Glands

located in the wall of the first few cm of the duodenum

Makes sense, because this is the area right before bicarb rich secretions from the pancreas and GB enter via the sphincter of oddi

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20
Q

Why do peptic ulcers often occur in the duodenum, as well as the stomach?

A

Brunner’s glands are inhibited by sympathetic stimulation, leaving the duodenal bulb unprotected

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21
Q

What are the crypts of liberkuhn?

A

small pits over the entire surface of the SI

Comprised of goblet cells and enterocytes

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22
Q

What are enterocytes?

A

Cells that secrete large quantities of water and electrolytes

reabsorb the water and electrolytes along with the end products of digestion

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23
Q

They crypts of Lieberkuhn produce marked secretion of watery fluid into the intestines. How do they do this?

A
  1. actively secrete Cl
  2. Actively secrete bicarb

Secretion of these causes an electrical drag of positively charged Na ions through the membrane into the secreted fluid

This mass movement causes osmotic movement of water into the gut

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24
Q

What is the life cycle of an intestinal epithelial cell?

A

5 days

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25
Q

The most important regulator of SI secretion is:

A

local enteric nervous reflexes

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26
Q

How dose the mucosa of the LI differ from the SI?

A

Both have crypts of lieberkuhn

but the LI contains no villi

The epithelial cells only secrete mucus

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27
Q

What does elevated Parasympathetic stimulation of the LI cause?

A

Excess mucus secretion

Ropy, mucoid diarrhea

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28
Q

What are polyscaccharides?

How are they formed?

A

monosaccharides bound to one another by condensation:

A H+ is removed from one monosaccharide and the OH- is removed from another to form water

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29
Q

What is hydrolysis?

A

The opposite of condensation

returning the H and OH from H2O, thereby separating polysaccharides into monosaccharides

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30
Q

Almost the entire fat portion of the diet consiste of ______

A

triglycerides

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31
Q

What is the composition of a triglyceride?

A

Three fatty acid molecules condensed with a single glycerol

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32
Q

How is the digestion of carbs, fats, and proteins similar?

How is it dissimilar?

A

All three are broken down by hydrolysis

The only difference is the types of enzymes required to promote hydrolysis for each type

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33
Q

All of the digestive enzymes are _______

A

proteins

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34
Q

Where does carbohydrate digestion begin?

A

The mouth

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35
Q

Starches and maltose are broken down into _______

Lactose is broken down into _______

Sucrose is broken down into _____

A

Glucose

Galactose and Glucose

Fructose and Glucose

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36
Q

Proteins are amino acids bound by

A

peptide linkages

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37
Q

Why is cholesterol considered to be a fat if it contains no fatty acids?

A

Sterol compound, but it exhibits similar physical and chemical characteristics

derived from fats and metabolized similarly

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38
Q

Most protein digestion results from:

A

pancreatic proteolytic enzymes:

trypsin, chymotripsin, carboxypolypeptidase, elastase

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39
Q

Where are peptides finally broken down into amino acids?

A

inside the cytosol of the enterocyte

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40
Q

What is the first step in fat digestion?

A

Emulsification of fat by bile acids and lecithin

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41
Q

Why is it so critical that fats be emulsified?

A

Lipases are water soluble. They can only attach fat globules on their surface, so the surface area has to be high

42
Q

What is the role of bile salts in fat digestion?

A

They aid in reabsorption by forming micelles

They “ferry” nonsoluble fatty acids from to the brush border epithelial cells

They are absorbed into the blood via the epithelium

43
Q

No cholesterol is absorbed from the gut without the help of:

A

bile salt micelles

44
Q

Why is the stomach such a poorly absorptive area?

A

lacks villus

tight cell junctions

45
Q

Only highly _____ soluble substances can be absorbed in small quantities from the stomach

A

lipid

aspirin and alcohol

46
Q

What are valvulae conniventes

A

Folds of Kerckring

increase the surface area of the absportive mucosa by about three-fold

47
Q

Describe how the intestinal mucosa surface area is increased

A

Folds of Kerckring (3x)

Villi (10x)

Brush border (microvilli) (20x)

Combined, increase absoprtive area by 1000x

48
Q

How is sodium reabsorbed from the gut

A

Actively pumped out of epithelial cells into the blood via ATPase pump, which reduces the sodium concentration inside the cell

sodium moves down this steep gradient from the chyme into the epithelial cell

49
Q

Aldosterone triggers intestinal sodium reabsorption primarily in the:

A

Large intestines

50
Q

How is bicarb reabsorbed in the small intestines?

A

Sodium-hydrogen countertransport

These H+ ions combine with HCO3 to form H2CO3

Converted into H2O and CO2

CO2 is blown off through the lungs

51
Q

What role does the Large Intestine play in bicarb regulation?

A

Can secrete HCO3- in exchange for absorption of Cl-

Provides the LI with bicarb to neutralize the acid products formed by bacteria

52
Q

How does cholera cause life-threatening diarrhea?

A

Cholera toxin enters epithelial cells and stimualtes cAMP formation

Opens tremendous numbers of Cl channels, allowing Cl to flow rapidly from inside the cell tot he intestines

activates a sodium pump that pumps sodium ions into the crypts to keep a net charge

Water pours into the gut

53
Q

Besides sodium, what electrolytes are actively reabsorbed in the intestines?

A

calcium, iron, potassium, magnesium

phosphate

54
Q

How is glucose reabsorbed?

A

Transported by a sodium co-transport (SGLT1) into the epithelial cell

diffues through GLUT2 into the blood

55
Q

How much sodium and chloride are lost in the feces each day?

A

Almost none

56
Q

What are alternative names for the proximal and distal colon

A

Correspond with their roles:

absorbing colon

storage colon

57
Q

How does sodium transport in the LI differ from the SI?

A

LI has much tighter junctions, so there is less backleak

the LI can absorb sodium ions more completely and against a stronger gradient,

especially when aldosterone is present

This means the LI is also ideal for reabsorbing water

58
Q

How much fluid can the intestines absorb each day?

A

5-8 L

the rest is excreted as feces

59
Q

What is the composition of feces?

A

75% water

25% solid matter which is composed of:

dead bacteria, fat, inorganic matter, protein, and roughage

60
Q

What causes the brown color of feces?

A

stercobilin and urobilin, both derivatives of bilirubin

61
Q

What causes the odor of feces?

A

bacterial actions produce:

indole

skatole

mercaptans

and hydrogen sulfide

62
Q

_______, _______, and ________ increase the rate of gastric motility.

How?

A

Gastrin

Motilin

Vagus PNS

Lower the threshold potential

63
Q

______ and _____ decrease gastric motility. How?

A

SNS

Secretin

raise the threshold potential

64
Q

What stimulates secretion of CCK?

What does it do?

A

products of fat digestion in the duodenum

inhibits food intake

reduces gastric motility

decreases gastric emptying

65
Q

What is the effect of hyperglycemia on gastric emptying?

Hypoglycemia?

A

Decreases

Increases

66
Q

Parietal cells secrete what? (3)

A

HCl

intrinsic factor

gastroferrin

67
Q

Chief cells secrete what?

A

pepsinogen

acidic lipase

68
Q

In the pyloric glands, G cells secrete ______

Enterochromaffin-like cells secrete ______

and

D cells secrete ______

A

gastrin

histamine

somatostatin

69
Q

What are the three main actions of gastric HCl?

A
  1. dissolve food
  2. act as a bactericide
  3. convert pepsinogen to pepsin
70
Q

A high rate of gastric secretion results in _______ in the venous blood

A

“alkaline tide”

may result in alkaline urine as well

71
Q

What hormones inhibit gastric acid secretion?

A

Somatostatin

secretin

CCK

GLP1

ANP

Prostaglandins

72
Q

What stimulates acid secretion?

A

vagus nerve –> Ach–>Gastrin –>Histamine–> Parietal cells make acid

ALSO:

caffeine

calcium

ghrelin

73
Q

What is special about gastric lipase?

A

Unlike pancreatic and intestinal lipases, it can be active in an acidic environment

74
Q

_________ and ________ protect the mucosal barrier by stimulating secretion of mucus and bicarb and inhibiting acid secretion

A

prostaglandins

nitric oxide

75
Q

The cephalic phase of gastric secretion is mediated by the ______ nerve via the _____ plexus

A

vagus

myenteric

76
Q

Hyperglycemia inhibits _______ and increases _______ in the stomach

A

motility

secertion

77
Q

What are the two main stimuli of the gastric phase?

A
  1. distention of the stomach (vagus and enteric local reflex)
  2. prescen of digested protein (stimulates gastrin)
78
Q

Trace the small intestines

A

duodenum

treitz ligament

jejunum

ileum

ileocecal valve

79
Q

The digestion and absorption of fat occurs in four phases:

A
  1. emulsification and lipolysis
  2. micelle formation
  3. fat absorption
  4. resynthesis of triglycerides and phospholipids
80
Q

Calcium is primarily reabsorbed in the:

A

ileum

81
Q

Why are bile salts important in the regulation of calcium uptake

A

Bile salts enhance calcium absorption by facilitating the absorption of Vitamin D, which is fat soluble

Anything that decreases fat absorption will decreases Ca levels

82
Q

Following a massive hemorrhage, the intestinal cells will start reabsorbing more iron after about three days.

Why?

A

Intestinal stem cells in the crypts of Lieberkuhn sense the need

they take three days to develop and migrate to the tips of the villi, where they absorb iron

83
Q

Ileogastric reflex inhibits _____ when ______

A

gastric motility

ileum is distended

84
Q

Intestinointestinal Reflex inhibits _______ when ______

A

intestinal motility

one part of the intestines is overdistended or irritated

85
Q

Gastroileal reflex stimulates ______ when _____

A

ileal motility and relaxation of ileocecal sphincter

gastric motility and secretion is increased

86
Q

Trace the large intestines

A

cecum

ascending

transverse

descending

sigmoid

rectosigmoid sphincter

internal anal sphincter

external anal sphincter

87
Q

What are paneth cells?

A

small intestinal cells near the crypts

produces defensins and other antimicrobial peptides and lysosomes

88
Q

What are peyer patches?

A

lymph nodules in the SI containing collections of lymphocytes, plasma cells, and macrophages

Play a major role in antigen processing and immune defense

89
Q

What is special about intestinal macrophages?

A

When they phagocytize pathogenic bacteria, they don’t produce any harmful cytokines

90
Q

What is the largest solid organ in the body?

A

Liver

91
Q

What are kupffer cells?

A

liver macrophages

largest population of tissue macrophages in the body

central to innate immunity and healing after liver injury

Also produce bilirubin

92
Q

List the cells in the liver involved in immunity

A

Kupffer (macrophages)

Stellate

Natural Killer Cells

93
Q

What is a choleretic agent?

A

Substance that stimulates the liver to secrete bile

94
Q

List 4 choleretics

A
  1. high concentration of bile salts
  2. secretin
  3. CCK
  4. Vagal Stimulation
95
Q

What happens to heme and globin once they are separated?

A

Globin is further broken down in AAs which are recycled to make proteins

Heme is converted biliverdin and iron

Iron attaches to transferrin and is stored in the liver or used by the bone marrow to make new RBCs

Biliverdin is converted to bilirubin and released into the plasma, where it binds to albumin

Bound to albumin it is called “unconjugated bilirubin”

96
Q

What happens to unconjugated bilirubin?

A

In the plasma, serves as an antioxidant and provides cytoprotection

Once it gets to the liver, converted to water-soluble conjugated bilirubin

Excreted in the bile

97
Q

What happens to conjugated bilirubin after it’s been secreted in bile?

A

Once it makes its way from the duodenum to the distal ileum, it is deconjugated by bacteria and converted to urobilinogen

Urobilinogen is reabsorbed in the intestines and transported to the kidney

Excreted as urobilin

Gives urine its yellow color

98
Q

How are amino acids converted to carbohydrates?

A

Deamination

Removal of Ammonia

99
Q

Why is elevated LDH indicative of hemolysis?

A

LDH is largely found inside RBCs

100
Q

Why are elevated ALT and AST indications of liver damage?

A

Both are enzymes in hepatocytes that are critical in deamination

If they are present in the blood stream, it means liver cells are breaking down and these enzymes are escaping

101
Q

How long does the liver store Vitamin A?

A

Several years!

102
Q

Why is the exocrine pancreas called “exocrine”

A

it’s secreting substances into the inner lumen of the intestines, which is actually the outside of the body

Patho 2 (24 decks)

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