GI - Physiology (GI Absorption& Peyer patches)

Question 1

What kind of carbohydrates are absorbed by enterocytes?

Answer 1

Only monosaccharides (glucose, galactose, fructose) are absorbed by enterocytes

Question 2

Which carbohydrate(s) does the SGLT1 transporter in the GI tract transport? On what does the activity of this transporter depend?

Answer 2

Glucose and galactose are taken up by SGLT1 (Na+ dependent)

Question 3

Which carbohydrate(s) does the GLUT-5 transporter in the GI tract transport, and what is the transport mechanism?

Answer 3

Fructose is taken up by facilitated diffusion by GLUT-5

Question 4

Which carbohydrate(s) does the GLUT-2 transporter in the GI tract transport?

Answer 4

All (monosaccharides - glucose, galactose, fructose) are transported to blood by GLUT-2

Question 5

What is the purpose of the D-xylose absorption test?

Answer 5

D-xylose absorption test: distinguishes GI mucosal damage from other causes of malabsorption

Question 6

In what form and where is Iron absorbed in the GI tract?

Answer 6

Absorbed as Fe2+ in duodenum

Question 7

Where in the GI tract is Folate absorbed?

Answer 7

Absorbed in jejunum and ileum

Question 8

Where in the GI tract is Vitamin B12 absorbed? What else is absorbed at this location? What is required for Vitamin B12 absorption?

Answer 8

Absorbed in terminal ileum along with bile acids, requires intrinsic factor

Question 9

Again, give where each of the following vitamins/minerals are absorbed: Folate, Iron, & Vitamin B12.

Answer 9

Iron - Duodenum; Folate - Jejunum and Ileum; B12 - Terminal Ileum; Think: “Iron Fist, Bro”

Question 10

What are Peyer patches, and where are they found? Be specific with location.

Answer 10

Unencapsulated lymphoid tissue found in lamina propria and submucosa of ileum

Question 11

What special cells do Peyer patches contain, and what function do these cells serve?

Answer 11

Contain specialized M cells that sample and present antigens to immune cells.

Question 12

Where in Peyer patches are B cells stimulated? Into what specific cell type do they differentiate, and where do these differentiated cells reside?

Answer 12

B cells stimulated in germinal centers of Peyer’s patches differentiate into IgA-secreting plasma cells, which ultimately reside in the lamina propria

Question 13

What kind of immunoglobulin addresses intraluminal antigen in the GI tract? What special component does it have, and how does it get to the lumen?

Answer 13

B cells stimulated in germinal centers of Peyer’s patches differentiate into IgA-secreting plasma cells, which ultimately reside in the lamina propria. IgA receives protective secretory component and is then transported across the epithelium to the gut to deal with intraluminal antigen. Think: “IgA, the Intra-Gut Antibody. And always say ‘secretory IgA’”