Lower GI Histology

Question 1

What are the layers of the intestinal wall?

Answer 1

From inside to outside:

mucosa with lamina propria and muscularis mucosa

submucosa

muscularis layers

serosa

Question 2

In what layer of the intestine are the villi and crypts found?

Answer 2

mucosa

Question 3

What lymphatic plexus is found in the villi?

Answer 3

lacteal.

They have branches that surround a lymphoid nodule in the submucosa.

Question 4

What are characteristics of the duodenum?

Answer 4

It has villi with a wide, leaflike shape

Deep crypths of lieberkuhn

Brunner’s glands with excretory ducts in submucosa

Question 5

What gland is found only in the muscularis mucosae of the duodenum?

Answer 5

Brunner’s gland

Question 6

What patch is found only in the submucosa of the ileum?

Answer 6

Peyer’s patches. They are lymphoid aggregates.

Question 7

What are the crypts of liberkuhn?

Answer 7

Simple tubular glands within the intestinal mucosa.

They open between adjacent villi and extend to muscularis mucosa.

Question 8

What cells are found in the crypts of lieberkuhn?

Answer 8

Goblet cells

Enterocytes

Paneth cells

Enteroendocrine cells

Question 9

What are physical characteristics of the crypts of lieberkuhn?

Answer 9

Basal nucleus

Perinuclear Golgi

Apical brush border

Question 10

What is the function of enterocytes?

Answer 10

production of disaccharidases

Absorption of proteins, carbohydrates and lipids.

Question 11

Enzymes present on the apical border of the enterocytes are important in what?

Answer 11

carbohydrate digestion

Question 12

What enzyme produced by enterocytes is necessary for the activation of pancreatic zymogens and proenzymes?

Answer 12

enteropeptidase

Question 13

What enzyme do paneth cells produce?

Answer 13

lysozyme; it controls the intestinal flora.

Question 14

Where are paneth cells found?

Answer 14

in the crypt (basal area)

Question 15

What type of blood component is found in the paneth cells?

Answer 15

eosinophilic granules

Question 16

What do enteroendrocrine cells produce?

Answer 16

peptide hormones and serotonin.

Question 17

You are studying the GI tract and obtain a sample of endodermal stem cells. What will these stem cells differentiate into?

Answer 17

enteroendocrine cells.

Question 18

Where are the glands of Brunner found?

Answer 18

submucosa of duodenum

Question 19

What are the glands of brunner responsible for?

Answer 19

Formation of bicarbonate and mucus.

They are also necessary to neutralize gastric acid.

Question 20

What are the histologic characteristics of the jejunum?

Answer 20

Long and narrow villi

Crypts of Lieberkuhn present

No glands in submucosa

Question 21

What are the histologic characteristics of the ileum?

Answer 21

Long and narrow villi

Crypts of Lieberkuhn Present

No glands in submucosa

Question 22

The large intestine is comprised of what type of epithelium?

Answer 22

simple columnar

Question 23

The large intestine contains ____, but no ____

Answer 23

crypts, villi

Question 24

Why does the large intestine secrete mucus?

Answer 24

for lubrication.

Question 25

What is the prominent cell of the large intestine?

Answer 25

goblet cells

Question 26

What are three functions of the large intestine?

Answer 26

Absorption of fluid Formation of fecal mass Continuation of digestion initiated in small intestine.

Question 27

What type of junctions are found between intestinal cells?

Answer 27

Tight junctions. THey are occluding junctions that contain claudins and occludins.

Question 28

What do the occluding junctions between the intestinal junctions prevent?

Answer 28

paracellular transport.

Question 29

If there is a defect in the tight junctions, what is able to pass inbetween the junctions?

Answer 29

lamina propria.

Question 30

Paneth cells contain what blood componentn?

Answer 30

basophils

Question 31

Paneth cells contain what type of secretory granules at the apical surface?

Answer 31

acidophilic secretory granules

Question 32

What do patheth cells secrete

Answer 32

Lysozyme Defensins Tumor necrosis factor alpha

Question 33

You are studying the GI tract and introduce foreign bacteria to it. What enzyme is secreted to attack the bacteria, and what type of cell secretes it?

Answer 33

Lysozyme is secreted by the paneth cells in order to degrade bacteria.

Question 34

What is the purpose of the secretion of defensins by paneth ells?

Answer 34

It increases membrane permeability of target organisms.

Question 35

Paneth cells secrete various enzymes and proteins. What is another function of paneth cells?

Answer 35

To phagocytize some microorganisms and help regulate intestinal flora.

Question 36

What does the mucosal layer coat?

Answer 36

Intestinal epithelial luminal surface.

Question 37

What are the two layers of the mucosal layer?

Answer 37

outer layer (microorganisms) Inner layer: antimicrobial proteins that resist microbial penetration.

Question 38

Where are toll-like receptors found?

Answer 38

on the surface of enterocytes.

Question 39

What do toll-like receptors recognize?

Answer 39

structurally conserved molecules broadly shared by pathogens but distinguishable from host molecules.

Question 40

What is the pattern of the immune surveillance syste?

Answer 40

1. Antigen binds to toll-like receptor on enterocyte surface. 2. B-cell activating factor is produced 3. B cells in lamina propria mature into plasma cells -> antibodies.

Question 41

Once B cells mature into plamsa cells (antibodies), what happens to the antigen?

Answer 41

It is taken up by M cells associated with Peyer patch in the intestinal mucosa.

Question 42

Once antigens are taken up by M cells, where are the antigens transported?

Answer 42

to lymphocytes located in pockets in folds of M cells.

Question 43

Once antigens are transported to lymphocytes, what do the antigens bind to on the surface of lymphocytes?

Answer 43

Ig receptors.

Question 44

Once antigens are bound to Ig receptors on lymphocytes, where is the Ig bound antigen transferred?

Answer 44

to dendritic cells in lamina propria.

Question 45

When lymphocytes are transferred to dendritic cells in the lamina propria, what do the dendritic cells then do?

Answer 45

interact with T cells in lamina propria to activate an immune response.

Question 46

Where is the bulk of the body's immune defenses centered?

Answer 46

GALT

Question 47

What are the permenant structures in the GALT?

Answer 47

appendix Peyer's patches Mesenteric lymph nodes

Question 48

What does GALT contain?

Answer 48

lymphocytes neutrophils eosinophils

Question 49

In what region of the villi are peyer's patches found?

Answer 49

submucosa (under mucosal surface)

Question 50

What type of cells are found in peyer's patches?

Answer 50

B and T cells

Question 51

Peyer's patches contain high endothelial venules. What do HEVs do?

Answer 51

allow the entrace of lymphocytes into lymphoid organs from the bloodstream.

Question 52

What is found on the mucosal covering of Peyer's patches?

Answer 52

M (microfold cells). They take particulate of an antigen and present it to antigen-presenting cells in the underlying lamina propria.

Question 53

What do antigen presenting cells do?

Answer 53

phagocytize an antigen and present it to helper and cytotoxic T cells, as well as B lymphocytes.

Question 54

What is the primary immunoglobulin produced by GALT?

Answer 54

IgA

Question 55

Where are IgA immunoglobulins synthesized and secreted?

Answer 55

They are secreted by plama cells in the lamina propria of the gut. They are picked up at the basal surface of enterocytes and transported across the cell.

Question 56

When in the cell, what is sIgA bound to in order to prevent degradation by proteolytic enzymes?

Answer 56

secretory component protein

Question 57

What is the function of secretory IgA?

Answer 57

It coats microorganisms, which inhibits microorganisms from binding to the epithelium.

Question 58

What is a protective mechanism used by the GI epithelium?

Answer 58

rapid cell turnover.

Question 59

How often is the lining of the stomach and small intestine replaced?

Answer 59

Every five days

Question 60

In the esophagus, where are new cells formed?

Answer 60

in the basal layer of stratified epithelium.

Question 61

Where are new cells formed in the small intestine?

Answer 61

in the crypts

Question 62

Where is the proliferative compartment found in the large intestine?

Answer 62

At the base of the crypt.

Question 63

What cells in the stomach are responsible for cell turnover?

Answer 63

surface and neck mucus cells Enteroendocrine cells Parietal cells Chief cells.

Question 64

What does the small intestine consist of?

Answer 64

Duodenum Jejunum Ileum