Lecture #35: Lower GI Histology II Flashcards Preview

Histology -- Zach H. > Lecture #35: Lower GI Histology II > Flashcards

Flashcards in Lecture #35: Lower GI Histology II Deck (33):
1

Where does carbohydrate digestion begin? 

Digestion of carbohydrates begins in the mouth. 

  • amylase hydrolyzes starch to form sugars
    • starch is hydrolyzed to disaccharides 
  • amylase is also secreted by the pancreas 

2

What is the role of amylase? 

  • Amylase hydrolyzes starch to form sugars, beginning in the mouth. 
    • starch is hydrolyzed to disaccharides 
  • Amylase is also secreted by the pancreas

3

Where are disaccharides broken down to monosaccharides? 

Occurs in brush border of small intestine. 

4

What cell type absorbs monosaccharides after they are broken down from disaccharides in the brush border of the small intestine? 

monosaccharides are absorbed by enterocytes 

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

5

Describe the sequential breakdown of proteins into amino acids; where do each of the steps occur? 

  • Digestion of proteins begins in the stomach. 
    • proteins are hydrolyzed to peptides
    • occurs through action of pepsin (activated from pepsiongen)
    • requires acidic environment of stomach
  • Polypeptide breakdown to peptides also occurs in the small intestine:
    • involves enzymes secreted by the pancreas: 
      • trypsin
      • chymotrypsin
      • elastase
      • carboxypeptidase
    • activation of pancreatic proteolytic enzymes is initiated by enteropeptidase (enterokinase) secreted by duodenal enterocytes
  • Further breakdown of oligopeptides to amino acids occurs in intestinal brush border
  • Transport of amino acids into enterocytes is via a carrier mediated process

6

Where does lipid digestion begin?

Digestion of lipids begins in the small intestine. 

7

What enzymes are involved in lipid digestion? 

  • pancreatic lipase 

8

What role does micelles and chylomicrons play in lipid digestion? 

  • pancreatic lipase emulsifies large droplets into smalle droplets and releases fatty acids and glycerol.
    • these combine with bile salts to form micelles 
  • Micelles can transport: 
    • fatty acids, monoglycerides, glycerol, phospholipids, cholesterol, and viatmains A and K 
    • pancreatic lipid esterase splits cholesterol esters into cholesterol and fatty acids 
  • Micelles are passively absorbed across enterocyte apical plasma membrane. 
    • requires fatty acid binding proteins (FABPs) in apical membrane 
  • Chylomicrons are formed by triglycerides that recombine with proteins (from RER). 
    • chylomicrons are enclosed within membranes in Golgi apparatus. 
    • these membranes fuse to the plasma membrane and allow exocytosis
  • Chylomicrons enter intercellular spaces and are taken up by central lacteals.
    • these are blind endings of lymphatic vessels within lamina propria that forms the content of the intercellular spaces within the villi. 
    • lacteals dump into the large lymphatic network (cisterna chyli) that carry lymph from the gut tract
    • chylomicrons will later enter the blood via the lymph ducts that enter the subclavian veins

9

What is the site of secretion, target, and effect of cholecystokinin?

  • Site or Secretion: 
    • upper intestinal mucosa (duodenum)
    • secreted in response to gastric contents 
  • Targets and Effects: 
    • acts on pyloric sphincter to slow down emptying of stomach
    • stimulates bile release from gallbladder 
    • stimulates secretion of pancreatic enzymes 
    • competitive inhibitor of gastrins 

10

What is the site of secretion, target, and effect of gastrin?

  • Site of Secretion: 
    • pyloric-antral portion of stomach 
  • Targets and Effects: 
    • stimulates HCl production by gastric parietal cells 
    • promotes growth of gastric mucosa 
    • stimulates gastric motility 
    • stimulates release of insulin by pancreatic beta cells 

11

What is the site of secretion, target, and effect of secretin?

  • Site of Secretion: 
    • epithelial cells of duodenum 
    • stimulated by acid contents of stomach 
  • Targets and Effects: 
    • enhances release of insulin by pancreatic beta cells 
    • stimulates bicarbonate secretion by pancreas 

12

Which hormone stimulates bicarbonate secretion by the pancreas?

Secretin

13

Which hormone enhances the release of insulin by pancreatic beta cells? 

Secretin 

14

Where is secretin secreted from? 

epithelial cells of duodenum 

15

What stimulates epithelial cells of duodenum to secrete secretin? 

stimulated by acid contents of stomach

16

In which portion of the stomach is gastrin secreted? 

pyloric-antral portion of stomach

17

Which hormone stimulates gastric motility, release of insulin by pancreatic beta cells, HCl production by gastric parietal cells, and promotes growth of gastric mucosa?

gastrin 

18

Where in the duodenum is cholecytokinin secreted from? 

upper intestinal mucosa (duodenum)

19

What causes the upper intestinal mucosa to secrete cholecystokinin from the duodenum? 

secreted in response to gastric contents 

20

Which hormone is a competitive inhibitor of gastrins?

cholecystokinin

21

What does cholecystokinin function to do? 

  • acts on pyloric sphincter to slow down emptying of stomach
  • stimulates bile release form gallbladder 
  • stimulates secretion of pancreatic enzymes 

22

What type of muscle makes up the external and internal anal sphincters? 

  • Internal Anal Sphincter = Smooth Muscle 
  • External Anal Sphincter = Skeletal Muscle 

23

What type of epithelium is the anus lined by? 

stratified squamous epithelium 

24

Which of the following best describes the olfactory mucosa? 

a) stratified columnar epithelium with goblet cells and a distinct basement membrane.

b) simple ciliated columnar epithelium with goblet cells and a distinct basement membrane. 

c) stratified, non-keratinized epithelium lacking goblet cells with thick basement membrane.

d) pseudostratified columnar epithelium lacking goblet cells with no distinct basement membrane.

d) pseudostratified columnar epithelium lacking goblet cells with no distinct basement membrane.

25

Which of the following is not a necessary part of the respiratory membrane ?

a) pneumocyte I 

b) basal lamina of pneumocyte I 

c) dust cells (pulmonary macrophages) 

d) basal lamina of endothelial cell  

e) endothelial cell

c) dust cells (pulmonary macrophages) 

26

Which of the following is characteristic of an arteriole? 

a) thick tunica adventitia and large lumen

b) thick tunica media in relation to size of lumen

c) thin tunica media and relatively large lumen 

d) large blood-filled lumen 

e) large amounts of elastic fibers in the tunica media

b) thick tunica media in relation to size of lumen

27

Where is the body of a normal, healthy individual would you expect most erythrophagocytosis to be occurring? 

a) marginal zone in spleen 

b) medulla of thymus 

c) hematopoietic cord in bone marrow 

d) Cord of Billroth in spleen

e) paratrabecular sinus in lymph node

 

d) Cord of Billroth in spleen

28

Which of the followingsequences best describes the flow of red blood cells through the spleen? 

a) trabecular arteries, central arteries, splenic arteries, penicillus, venous sinuses 

b) splenic artery, central arteries, trabecular arteries, venous sinuses, penicillus

c) splenic artery, central arteries, trabecular arteries, venous sinuses, penicillus

d) trabecular arteries, splenic arteries, central arteries, penicillus, venous sinuses 

e) splenic artery, trabecular arteries, central arteries, penicillus, venous sinuses

e) splenic artery, trabecular arteries, central arteries, penicillus, venous sinuses

29

The simple cuboidal epithelium of this portion of the kidney tubule is composed of cells in the form of truncated pyramids which are characterized by basal striations that mark the location of mitochondria. 

a) proximal convoluted tubule

b) descending thin segment of the loop of Henle

c) ascending thick segment of the loop of Henle

d) distal convoluted tubule

e) collecting duct 

a) proximal convoluted tubule

30

Renin is secreted by which of the following? 

a) liver

b) macula densa cells 

c) atrial cells of the heart 

d) mesangial cells 

e) juxtaglomerular cells 

e) juxtaglomerular cells

31

True or False: 

Micelles are passively absorbed across enterocyte apical plasma membranes. 

True 

32

Which enzyme splits cholesterol esters into cholesterol and fatty acids?

pancreatic lipid esterase 

33