GI 9 - The Intestines

Question 1

Name the cells in the intestines which secrete antibacterial enzymes ie Lyzozymes + Defensins:

Answer 1

Paneth cells

Question 2

Approx. how many microvilli are present on each enterocyte?

Answer 2

~ 3000 per cell

Question 3

What is the approx. total surface area of the GI tract? How much of this is the small intestine?

Answer 3

~ 30 m^2

Small intestines = ~ 20 m^2

Question 4

How does the small intestine have such massive surface area?

Answer 4

• Folds of Kerckring
• Villi + Crypts of Lieberkuhn
• Microvilli

Question 5

Where are plicae circulares found?

Answer 5

Small intestine

Question 6

What type of epithelial cells are found in the intestines?

Answer 6

Simple columnar epithelia

Question 7

Name the 2 types of starch that we can digest, the enzymes required for digestion, and the products of digestion:

Answer 7

Amylose -> Glucose + Maltose via Amylase

Amylopectin -> alpha-dextrins via Isomaltase

Question 8

Which monosaccharides are transported by SGLT1 into the enterocyte from the GI lumen?

Answer 8

Glucose

Galactose

Question 9

Which monosaccharides are transported by GLUT5 into the enterocyte from the GI lumen?

Answer 9

Fructose

Question 10

How do monosaccharides move across the basolateral membrane of the enterocyte?

Answer 10

GLUT2

Question 11

Which transporters are present on the apical membrane of the enterocyte for carbohydrate absorption?

Answer 11

SGLT1

GLUT5

Question 12

Which enzymes to break down carbohydrates are present on the brush-border?

Answer 12

• Maltase
• Isomaltase
• Amylase
• Lactase
• Sucrase

Question 13

Which enzymes to break down proteins are present on the brush-border?

Answer 13

• Trypsin
• Chemotrypsin
• Elastase
• Carboxypeptidase A + B

Question 14

Which transporters can move amino acids and peptides into the enterocyte, from the GI lumen?

Answer 14

Na+-AA symporter

PEPT1

Question 15

What causes micelles to fall apart, allowing the absorption of fats into the enterocytes?

Answer 15

Acidic brush-border (formed by Na+/H+ exchanger)

Question 16

What are the components of a chylomicron?

Answer 16

• Triacylglycerides
• Cholesterol
• Phospholipids
• ApoB-48 (protein)

Question 17

Where are chylomicrons formed, and what is their function?

Answer 17

Enterocytes

Transport dietary lipid from intestines to Liver + Adipose cells

Question 18

Which electrolyte must be present for the absorption of glucose, water and other electrolytes?

Answer 18

Na+ - forms concentration/osmotic gradient

Question 19

What is the blood supply to the small intestines?

Answer 19

Superior mesenteric artery

Question 20

What is the function of the proximal half of the large intestine?

Answer 20

Absorption of minerals + H2O

Question 21

What is the function of the distal half of the large intestine?

Answer 21

Storage and mucous secretion

Question 22

What is the blood supply of the ascending colon, and proximal transverse colon?

Answer 22

SMA:

• Ileocolic
• Right colic
• Middle colic

Question 23

What is the blood supply to the distal transverse colon, and descending colon?

Answer 23

IMA:

• Left colic
• Sigmoid arteries

Question 24

What structures are present at the Caecum?

Answer 24

• Ileocaecal valve

- Appendix

Question 25

The superior rectal artery is the continuation of which artery?

Answer 25

IMA - becomes sup. rectal when passes into pelvis

Question 26

What is the taenia coli?

Answer 26

3 narrow bands of longitudinal muscle running the length of the large intestine - except in rectum, anal canal and appendix

Question 27

At what point does the colon stimulate the urge to defecate?

Answer 27

When rectum ~ 25% full

Question 28

Is the internal anal sphincter controlled by the parasympathetic or sympathetic nervous system?

Answer 28

Parasympathetic