Lower GI Histology II Flashcards Preview

A. White- Histology > Lower GI Histology II > Flashcards

Flashcards in Lower GI Histology II Deck (39):
1

Where does the digestion of carbohydrates begin?

in the mouth

2

Amylase ______ starch to form ______.

hydrolyzes, sugars

3

What is starch hydrolyzed to?

disaccharides

4

What also secretes amylase?

the pancreas

5

What are disaccharides are broken down to?

monosaccharides

6

Where does the degradation of disacchrides occur?

in brush border of small intestine

7

What absorbs monosaccharides?

enterocytes

8

What does the absorption of monosaccharides entail?

• Involves energy-dependent mediator-specific carriers:
• Na+-dependent sugar glucose transporter-1 (SGLT-1)

9

Where does the digestion of proteins begin?

in the stomach

10

What are proteins hydrolyzed to?

peptides

11

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

True

12

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

in the small intestine, peptides

13

What enzymes does the breakdown of polypeptides involve?

Trypsin, chymotrypsin, elastase, carboxypeptidase

14

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

true

15

Where does further breakdown of oligopeptides to amino acids occur?

in intestinal brush border

16

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

carrier-mediated

17

Where does the digestion of lipids begin?

in the small intestine

18

Lipids enter the small intestine as _______ ________.

triglyceride droplets

19

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

lipase, fatty acids, glycerol, micelles

20

What do micelles transport?

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

21

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

true

22

How are micelles passively absorbed across enterocyte apical plasma membrane?

through fatty acid binding proteins (FABPs) in apical membrane

23

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

Requires acyl-CoA synthetase and acyltransferase:
• Found in membranes of enterocyte SER

24

Describe chylomicrons

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

25

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

Triglycerides, proteins, chylomicrons

26

Chylomicrons will later enter the blood via what?

the lymph ducts that enter the subclavian veins

27

Chylomicrons enter intercellular spaces and are taken up by what?

central lacteals

28

What are central lacteals?

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

29

What do the lacteals dump into?

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

30

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

in the villi, liver, hepatic portal system

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.

true

32

Describe the site of secretion for cholecystokinin.

• Upper intestinal mucosa (duodenum)
• Secreted in response to gastric contents

33

What does cholecystokinin target and effect?

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

34

Describe the site of secretion for gastrin.

Pyloric-antral portion of stomach

35

What does gastrin target and effect?

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

36

Describe the site of secretion for secretin.

• Epithelial cells of duodenum
• Stimulated by acid contents of stomach

37

What does secretin target and effect?

• Enhances release of insulin by pancreatic β cells
• Stimulates bicarbonate secretion by pancreas

38

What is the epithelium of the anal canal?

stratified squamous epithelium

39

What type of muscle is the external anal sphincter?

skeletal