Lecture 21 Flashcards

1
Q

Small intestine has 3 parts:

A
  1. duodenum
  2. jejunum
  3. ileum
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2
Q

Histology of the Small Intestine: structures that increase surface area

A
  1. plica circularis
  2. villi
  3. microvilli
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3
Q

plica circularis

A
  • permanent ½ inch tall folds that contain part of submucosal layer
  • not found in lower ileum
  • can not stretch
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4
Q

villi:

A
  • 1 Millimeter tall
  • Core is lamina propria of mucosal layer
  • Contains vascular capillaries and lacteals
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5
Q

microvilli:

A

cell surface feature known as brush border

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6
Q

Functions of Microvilli:

A
  1. Absorption and digestion
  2. Digestive enzymes found at cell surface on microvilli
  3. Significant cell division within intestinal glands
    proteins
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7
Q

Roles of Intestinal Juice & Brush-Border Enzymes:

A
  1. Submucosal layer has duodenal glands

2. Mucosal layer contains intestinal glands

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8
Q

Submucosal layer secretes

A

alkaline mucus

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9
Q

Mucosal layer:

A

Crypts of Lieberkuhn

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10
Q

Crypts of Lieberkuhn :

A
  • secretes intestinal juice
  • brush border enzymes
  • paneth cells secrete lysozyme kills bacteria
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11
Q

Digestion of Carbohydrates:

mouth

A

salivary amylase

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12
Q

Digestion of Carbohydrates:Esophagus & stomach—

A

nothing happens

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13
Q

Digestion of Carbohydrates: Duodenum—-

A

pancreatic amylase

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14
Q

Digestion of Carbohydrates: brush border enzymes

A

act on disaccharides

  • produces monosaccharides
  • lactose intolerance
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15
Q

Lactose Intolerance:

A

Mucosal cells of small intestine fail to produce lactase

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16
Q

Digestion of Proteins: stomach

A
  1. HCl denatures or unfolds proteins

2. pepsin turns proteins into peptides

17
Q

Digestion of Proteins: pancreas

A
  1. digestive enzymes split peptide bonds between different amino acids
  2. brush border enzymes split off amino acid at amino end of molecule
18
Q

Digestion of Lipids: mouth

A

lingual lipase

19
Q

Digestion of Lipids: small intestine

A
  1. emulsification by bile
  2. pancreatic lipase splits into fatty acids & monoglyceride
  3. no enzymes in brush border
20
Q

Digestion of Nucleic Acids:

A
  1. Pancreatic juice = RNA and DNA
  2. Nucleotides produced are digested by enzymes
  3. absorbed by active transport
21
Q

Absorption of Monosaccharides:

A

into and out of epithelial cell

22
Q

Absorption into epithelial cell

A
  1. glucose & galactose=sodium symporter

2. fructose=facilitated diffusion

23
Q

Movement out of epithelial cell into bloodstream:

A

by facilitated diffusion

24
Q

Absorption of small fatty acids:

A

enter cells & then blood by simple diffusion

25
Absorption of larger lipids:
exist only within micelles (bile salts coating)
26
Lipids enter cells by
simple diffusion leaving bile salts behind in gut
27
Bile salts reabsorbed into
blood & reformed into bile in the liver
28
Inside epithelial cells fats are
rebuilt and coated with protein to form chylomicrons
29
Chylomicrons leave intestinal cells by
exocytosis into a lacteal - travel in lymphatic system - removed from the blood by the liver and fat tissue
30
Sources of electrolytes:
GI secretions & ingested foods and liquids
31
Enter epithelial cells by
diffusion & secondary active transport
32
sodium & potassium move =
Na+/K+ pumps (active transport)
33
chloride, iodide and nitrate =
passively follow
34
iron, magnesium & phosphate ions =
active transport
35
Intestinal Ca+ absorption requires
vitamin D & parathyroid hormone
36
Fat-soluble vitamins:
travel in micelles & are absorbed by simple diffusion
37
Water-soluble vitamins
absorbed by diffusion
38
B12 combines with
intrinsic factor before it is transported into the cells | -receptor mediated endocytosis
39
Absorption of Water:
by osmosis | 9 L each day