Lecture 21

Question 1

Small intestine has 3 parts:

Answer 1

1. duodenum
2. jejunum
3. ileum

Question 2

Histology of the Small Intestine: structures that increase surface area

Answer 2

1. plica circularis
2. villi
3. microvilli

Question 3

plica circularis

Answer 3

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

Question 4

villi:

Answer 4

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

Question 5

microvilli:

Answer 5

cell surface feature known as brush border

Question 6

Functions of Microvilli:

Answer 6

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

Question 7

Roles of Intestinal Juice & Brush-Border Enzymes:

Answer 7

1. Submucosal layer has duodenal glands

2. Mucosal layer contains intestinal glands

Question 8

Submucosal layer secretes

Answer 8

alkaline mucus

Question 9

Mucosal layer:

Answer 9

Crypts of Lieberkuhn

Question 10

Crypts of Lieberkuhn :

Answer 10

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

Question 11

Digestion of Carbohydrates:

mouth

Answer 11

salivary amylase

Question 12

Digestion of Carbohydrates:Esophagus & stomach—

Answer 12

nothing happens

Question 13

Digestion of Carbohydrates: Duodenum—-

Answer 13

pancreatic amylase

Question 14

Digestion of Carbohydrates: brush border enzymes

Answer 14

act on disaccharides

• produces monosaccharides
• lactose intolerance

Question 15

Lactose Intolerance:

Answer 15

Mucosal cells of small intestine fail to produce lactase

Question 16

Digestion of Proteins: stomach

Answer 16

1. HCl denatures or unfolds proteins

2. pepsin turns proteins into peptides

Question 17

Digestion of Proteins: pancreas

Answer 17

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

Question 18

Digestion of Lipids: mouth

Answer 18

lingual lipase

Question 19

Digestion of Lipids: small intestine

Answer 19

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

Question 20

Digestion of Nucleic Acids:

Answer 20

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

Question 21

Absorption of Monosaccharides:

Answer 21

into and out of epithelial cell

Question 22

Absorption into epithelial cell

Answer 22

1. glucose & galactose=sodium symporter

2. fructose=facilitated diffusion

Question 23

Movement out of epithelial cell into bloodstream:

Answer 23

by facilitated diffusion

Question 24

Absorption of small fatty acids:

Answer 24

enter cells & then blood by simple diffusion

Question 25

Absorption of larger lipids:

Answer 25

exist only within micelles (bile salts coating)

Question 26

Lipids enter cells by

Answer 26

simple diffusion leaving bile salts behind in gut

Question 27

Bile salts reabsorbed into

Answer 27

blood & reformed into bile in the liver

Question 28

Inside epithelial cells fats are

Answer 28

rebuilt and coated with protein to form chylomicrons

Question 29

Chylomicrons leave intestinal cells by

Answer 29

exocytosis into a lacteal

• travel in lymphatic system
• removed from the blood by the liver and fat tissue

Question 30

Sources of electrolytes:

Answer 30

GI secretions & ingested foods and liquids

Question 31

Enter epithelial cells by

Answer 31

diffusion & secondary active transport

Question 32

sodium & potassium move =

Answer 32

Na+/K+ pumps (active transport)

Question 33

chloride, iodide and nitrate =

Answer 33

passively follow

Question 34

iron, magnesium & phosphate ions =

Answer 34

active transport

Question 35

Intestinal Ca+ absorption requires

Answer 35

vitamin D & parathyroid hormone

Question 36

Fat-soluble vitamins:

Answer 36

travel in micelles & are absorbed by simple diffusion

Question 37

Water-soluble vitamins

Answer 37

absorbed by diffusion

Question 38

B12 combines with

Answer 38

intrinsic factor before it is transported into the cells

-receptor mediated endocytosis

Question 39

Absorption of Water:

Answer 39

by osmosis

9 L each day