Week 2 - Summary of digestive hormones

Question 1

Gastrin

Answer 1

§ Stimulated by
distension of stomach
and the bolus entering
the stomach
§ Increases gastric
secretions

Question 2

Secretin

Answer 2

§ Stimulated by chyme
entering the duodenum
§ Decreases gastric
secretions
§ Stimulates pancreas to
secrete pancreatic juice
§ Stimulates bile
secretion from liver

Question 3

Cholecystokinin

Answer 3

§ Stimulated by chyme
entering the duodenum
§ Decreases gastric
secretions
§ Stimulates pancreas to
secrete pancreatic juice
§ Stimulates bile release
from gallbladder

Question 4

Absorption of Carbohydrates (4 steps)

Answer 4

1. Glucose is absorbed by symport with Na+ into intestinal epithelial cells
2. Symport is driven by a sodium gradient established by a Na+-K+ pump
3. Glucose moves out of the intestinal epithelial cells by facilitated diffusion
4. Glucose enters the capillaries of the intestinal villi and is carried through the hepatic portal vein to the liver

Question 5

Absorption of lipids

Answer 5

Fat is broken down into smaller globules by bile salts from the liver. This allows lipase to target the smaller globules and break it into monoglycerides and free fatty acids. These then assemble into Micelles which have a hydrophobic interior and hydrophilic exterior. The Micelles then release the the triglycerides and free fatty acids into the enterocytes (epithelium of the intestinal lumen). Monoglycerides fuse to become triglycerides and then form a chylomicron or lipoprotein which contain phospholipids and proteins. They then diffuse into the the lymphatic system which transports the compound into the blood. Muscles use this for energy and it is also stored in Adipose tissue.

Question 6

Absorption of protein (4 steps)

Answer 6

1. Acidic and most neutral amino acids are absorbed by symport into intestinal epithelial cells.
2. Symport is driven by a sodium gradient established by a Na+-K+ pump
3. Amino acids move out of intestinal epithelial cells
4. Amino acids enter the capillaries of the intestinal villi and are carried through the hepatic portal vein to the liver

Question 7

Large intestine route

Answer 7

Cecum -> colon -> retum -> anus

Question 8

What moves chyme up the ascending colon

Answer 8

Peristaltic contractions

Question 9

What moves chyme along the transverse and descending colon

Answer 9

Mass movements

Question 10

What stimulates movement in the large intestine

Answer 10

Local reflexes
Parasympathetic stimulation
Hormones – gastrin and cholecystokinin
Distension of the stomach
Chyme in the duodenum
Smell or thought of food