Lecture 21 Flashcards Preview

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Flashcards in Lecture 21 Deck (39):
1

Small intestine has 3 parts:

1. duodenum
2. jejunum
3. ileum

2

Histology of the Small Intestine: structures that increase surface area

1. plica circularis
2. villi
3. microvilli

3

plica circularis

-permanent ½ inch tall folds that contain part of submucosal layer
-not found in lower ileum
-can not stretch

4

villi:

-1 Millimeter tall
-Core is lamina propria of mucosal layer
-Contains vascular capillaries and lacteals

5

microvilli:

cell surface feature known as brush border

6

Functions of Microvilli:

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

7

Roles of Intestinal Juice & Brush-Border Enzymes:

1. Submucosal layer has duodenal glands
2. Mucosal layer contains intestinal glands

8

Submucosal layer secretes

alkaline mucus

9

Mucosal layer:

Crypts of Lieberkuhn

10

Crypts of Lieberkuhn :

-secretes intestinal juice
-brush border enzymes
-paneth cells secrete lysozyme kills bacteria

11

Digestion of Carbohydrates:
mouth

salivary amylase

12

Digestion of Carbohydrates:Esophagus & stomach---

nothing happens

13

Digestion of Carbohydrates: Duodenum----

pancreatic amylase

14

Digestion of Carbohydrates: brush border enzymes

act on disaccharides
-produces monosaccharides
-lactose intolerance

15

Lactose Intolerance:

Mucosal cells of small intestine fail to produce lactase

16

Digestion of Proteins: stomach

1. HCl denatures or unfolds proteins
2. pepsin turns proteins into peptides

17

Digestion of Proteins: pancreas

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

18

Digestion of Lipids: mouth

lingual lipase

19

Digestion of Lipids: small intestine

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

20

Digestion of Nucleic Acids:

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

21

Absorption of Monosaccharides:

into and out of epithelial cell

22

Absorption into epithelial cell

1. glucose & galactose=sodium symporter
2. fructose=facilitated diffusion

23

Movement out of epithelial cell into bloodstream:

by facilitated diffusion

24

Absorption of small fatty acids:

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