Physiology Flashcards

1
Q

Pancreatic Secretions: flow

A

Isotonic fluid;

low flow –> high Cl-

high flow –> high HCO3-

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2
Q

Pancreatic Secretions (4)

A

alpha-amylase

lipases

proteases

trypsinogen

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3
Q

Alpha-amylase

A

Pancreatic secretion

Role: starch digestion (1,4-glycosidic bonds)

secreted in active form

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4
Q

Lipases

A

Pancreatic secretion

Role: fat digestion

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5
Q

Proteases

A

Pancreatic secretion

Role: protein digestion

Includes: trypsin, chymotrypsin, elastase, carboxypeptidases

Secreted as proenzymes (zymogens)

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6
Q

Trypsinogen

A

Pancreatic secretion

Role: Converted to active enzyme trypsin (activation of other zymogens and cleaving of additional trypsinogen molecules into active trypsin –> positive feedback loop)

Converted to trypsin by enterokinase/enteropeptidase, brush border enzyme on duodenal and jejunal mucosa

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7
Q

Carb absorption

A

ONLY monosaccharides (glucose, galactose, fructose) absorbed by enterocytes

Glucose/galactose –> SGLT1 (Na+ dependent)

Fructose –> facilitated diffusion by GLUT-5

All transported to blood via GLUT-2

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8
Q

D-xylose absorption test

A

distinguishes GI mucosal damage from other causes of malabsorption

D-xylose = monosaccharide that does not require enzymes for digestion prior to absorption

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9
Q

Vitamin/mineral absorption

“Iron Fist, Bro”

A
  • Iron - absorbed as Fe2+ in duodenum
  • Folate - absorbed in small bowel
  • B12 - absorbed in terminal ileum (along with bile salts) / requires IF
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10
Q

Peyer patches

Intra-gut Antibody”

A

Unencapsulated lymphoid tissue

Found in lamina propria and submucosa of ileum

Contains specialized M cells that sample and present antigen to macrophages –> macrophages present processed antigen to lymphocytes –> triggers secretory immunity –> stimulates B cells in germinal centers of Peyer’s patches to differentiate into IgA-secreting plasma cells that reside in ileal lamina propria

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11
Q

Bile

Rate-limiting step of bile acid synthesis

Functions

A

Composed of bile salts (bile acids conjugated to glycine or taurine, changes pKa to make them water soluble), phospholipids, cholesterol, bilirubin, water, ions

Cholesterol 7alpha-hydroxylase catalyses rate-limiting step of bile acid synthesis

Functions:

Digestion and absorption of lipids and fat-soluble vitamins

Cholesterol excretion (body’s only means of eliminating cholesteroal)

Antimicrobial activity (via membrane disruption)

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12
Q

Bilirubin

Heme metabolism

Unconjugated bilirubin

Direct bilirubin

Indirect bilirubin

A

yellow-colored byproduct of hemoglobin (heme) metabolism

Heme is metabolized by heme oxygenase to biliverdin –> reduced to bilirubin

Unconjugated bilirubin removed from blood by liver, conjugated with glucuronate, and excreted in bile

Direct bilirubin - conjugated with glucuronic acid; water soluble

Indirect bilirubin - unconjugated, water insoluble

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13
Q

Dietary energy comes predominantly from protein, carbohydrate, and fat.

What does metabolism of 1 g of each yield?

A

Metabolism of 1 g of protein = 4 c

Metabolism of 1 g of carbohydrate = 4 c

Metabolish of 1 g of fat = 9 c

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