Lecture 24: GI histology II&III

Question 1

Structural features that increase surface area

Answer 1

Length of small and large intestine
Plicae circulares (valves of Kerckring)
Villi
Microvilli

Question 2

Plicae

Answer 2

Folds of the mucosa, each with submucosal core

Question 3

Crypt-villus system

Answer 3

Lamina propria core
Walls of villus have simple columnar with goblet cells
Each villus has a capillary plexus and lacteal
Crypts and villus constitute glands of the small intestine

Question 4

Microvilli

Answer 4

Covered with glycoprotein and glycocalyx
Made of bundles of actin with formin cap
Spectrin fibrils bind actin to intermediate filaments
Actin bound to plasma membrane by calmodulin/myosin I
Cross linked by villin and fimbrin

Question 5

Duodenum

Answer 5

Villi with leaf-like distal shape
Deep crypts of Lieberkuhn
Brunners glands with excretory ducts in submucosa

Question 6

Crypts of Lieberkuhn

Answer 6

Simple tubular glands
Open b/w adjacent villi and extend to muscularis mucosa
Contain goblet cells, paneth cells, enteroendocrine cells and enterocytes

Question 7

Enterocyte characteristics

Answer 7

Columnar epithelial cell
Basal nucleus, perinuclear golgi, brush border
Produces disaccharides
Involved in absorption of proteins, carbs, lipids
Produce enteropeptidase- activates pancreatic zymogens and proenzymes

Question 8

Paneth cells

Answer 8

Basal crypt cells
Prominent eosinophilic granules
Produce lysozyme to control intestinal flora

Question 9

Enteroendocrine cells

Answer 9

Produce peptide hormones and serotonin
May produce paracrine/autocrine secretions
Formed from endodermal stem cells

Question 10

Glands of brunner

Answer 10

Found in submucosa of duodenum

Responsible for formation of bicarbonate and mucus

Question 11

Jejunum

Answer 11

Villi longer and narrow
Crypts of Lieberkuhn present
No glands in submucosa

Question 12

Ileum

Answer 12

Villi narrow and shorter than jejunum
Crypts of Lieberkuhn present
No glands in subucosa

Question 13

Large intestine epithelium

Answer 13

Simple columnar

Crypts but no villi

Question 14

Function of large intestine

Answer 14

Secrete mucus
Goblet cell is prominent cell of large intestine
Absorb fluid
Form fecal mass

Question 15

Epithelial cells of GI tract are held together by

Answer 15

Occluding junctions

Question 16

Paneth cell secretions

Answer 16

Lysozyme- increase permeability of bacteria by degrading peptidoglycan coat
Defensins-increase membrane permeability of target organisms
Tumor necrosis factor
May phagocytize some microorganisms and help regulate flora

Question 17

Toll-like receptors

Answer 17

Type of pattern recognition receptor

Recognize structurally conserved molecules broadly shared by pathogens but distinguishable from host molecules (PAMPs)

Question 18

Components of GALT

Answer 18

Aggregations of lymphocytes, neutrophils, eosinophils

• Appendix
• Peyers patches
• Mesenteric lymph nodes

Question 19

Peyers patches

Answer 19

Contain B and T-cell dependent areas
Possess HEVs which facilitate entrance of lymphocytes into lymphoid organs
Contain specialized M cells-present particulate antigen to antigen-presenting cells
Antigen presenting cells and macrophages phagocytize antigen and present to helper T cells or B lymphocytes

Question 20

GALT produces what immunoglobulin

Answer 20

IgA

Question 21

How does sIgA avoid degradation in the cell

Answer 21

It is linked to a protein called secretory component

Question 22

Secretory IgA function

Answer 22

Coats microorganisms, inhibiting them from binding to epithelium

Question 23

In large intestine, proliferative compartment is located

Answer 23

At the base of the crypts

Question 24

In stomach, proliferative compartment is located

Answer 24

Stem cells found in the neck of gastric glands

Question 25

Epithelium of anus

Answer 25

Stratified squamous