Lower GI Histology II

Question 1

Where does the digestion of carbohydrates begin?

Answer 1

in the mouth

Question 2

Amylase ______ starch to form ______.

Answer 2

hydrolyzes, sugars

Question 3

What is starch hydrolyzed to?

Answer 3

disaccharides

Question 4

What also secretes amylase?

Answer 4

the pancreas

Question 5

What are disaccharides are broken down to?

Answer 5

monosaccharides

Question 6

Where does the degradation of disacchrides occur?

Answer 6

in brush border of small intestine

Question 7

What absorbs monosaccharides?

Answer 7

enterocytes

Question 8

What does the absorption of monosaccharides entail?

Answer 8

• Involves energy-dependent mediator-specific carriers:

* Na+-dependent sugar glucose transporter-1 (SGLT-1)

Question 9

Where does the digestion of proteins begin?

Answer 9

in the stomach

Question 10

What are proteins hydrolyzed to?

Answer 10

peptides

Question 11

True or false the digestion of proteins in the stomach occurs through action of pepsin.

Answer 11

True

Question 12

Where does the breakdown of polypeptides occur and what does it break down into?

Answer 12

in the small intestine, peptides

Question 13

What enzymes does the breakdown of polypeptides involve?

Answer 13

Trypsin, chymotrypsin, elastase, carboxypeptidase

Question 14

True or false, activation of pancreatic proteolytic enzymes is initiated by enteropeptidase (enterokinase) which are secreted by duodenal enterocytes.

Answer 14

true

Question 15

Where does further breakdown of oligopeptides to amino acids occur?

Answer 15

in intestinal brush border

Question 16

Transport of amino acids into enterocytes is via a ________ process.

Answer 16

carrier-mediated

Question 17

Where does the digestion of lipids begin?

Answer 17

in the small intestine

Question 18

Lipids enter the small intestine as _______ ________.

Answer 18

triglyceride droplets

Question 19

Pancreatic _______ emulsifies these large droplets into smaller droplets and releases ____ _____ and which _____ then combine with bile salts to form _______.

Answer 19

lipase, fatty acids, glycerol, micelles

Question 20

What do micelles transport?

Answer 20

• Fatty acids, monoglycerides, glycerol, phospholipids, cholesterol, and vitamins A and K.
• Pancreatic lipid esterase splits cholesterol esters into cholesterol and fatty acids.

Question 21

True or false, micelles are passively absorbed across enterocyte apical plasma membrane.

Answer 21

true

Question 22

How are micelles passively absorbed across enterocyte apical plasma membrane?

Answer 22

through fatty acid binding proteins (FABPs) in apical membrane

Question 23

How are monoglycerides and glycerol reesterified in the enterocyte SER to form triglyceride?

Answer 23

Requires acyl-CoA synthetase and acyltransferase:

• Found in membranes of enterocyte SER

Question 24

Describe chylomicrons

Answer 24

Chylomicrons are enclosed within membranes in Golgi apparatus.
• These membranes fuse to the plasma membrane and allow exocytosis.

Question 25

__________ recombine with _______ (from RER) to form _______.

Answer 25

Triglycerides, proteins, chylomicrons

Question 26

Chylomicrons will later enter the blood via what?

Answer 26

the lymph ducts that enter the subclavian veins

Question 27

Chylomicrons enter intercellular spaces and are taken up by what?

Answer 27

central lacteals

Question 28

What are central lacteals?

Answer 28

These are blind endings of lymphatic vessels within lamina propria that forms the content of the intercellular spaces within the villi.

Question 29

What do the lacteals dump into?

Answer 29

the large lymphatic network (cisterna chyli) that carry lymph from the gut tract

Question 30

Proteins and carbohydrates enter the blood vessels __ ___ ____ and are transported to the ____ via the ______ ______ ________.

Answer 30

in the villi, liver, hepatic portal system

Question 31

True or false, secretory activities of the GI tract are largely controlled by various hormones that, in turn, are under the influence of the contents of the GI tract.

Answer 31

true

Question 32

Describe the site of secretion for cholecystokinin.

Answer 32

• Upper intestinal mucosa (duodenum)

* Secreted in response to gastric contents

Question 33

What does cholecystokinin target and effect?

Answer 33

• Acts on pyloric sphincter to slow down emptying of stomach.
• Stimulates bile release from gallbladder
• Stimulates secretion of pancreatic enzymes
• Competitive inhibitor of gastrins

Question 34

Describe the site of secretion for gastrin.

Answer 34

Pyloric-antral portion of stomach

Question 35

What does gastrin target and effect?

Answer 35

• Stimulates HCl production by gastric parietal cells
• Promotes growth of gastric mucosa
• Stimulates gastric motility
• Stimulates release of insulin by pancreatic β cells

Question 36

Describe the site of secretion for secretin.

Answer 36

• Epithelial cells of duodenum

* Stimulated by acid contents of stomach

Question 37

What does secretin target and effect?

Answer 37

• Enhances release of insulin by pancreatic β cells

* Stimulates bicarbonate secretion by pancreas

Question 38

What is the epithelium of the anal canal?

Answer 38

stratified squamous epithelium

Question 39

What type of muscle is the external anal sphincter?

Answer 39

skeletal