secretion in the small intestine

Question 1

small intestines

Answer 1

• ~20ft/6m long
• most digestion and absorption takes place in SI
• absorption of 95% of H2O
• absorption of fat, carbs, proteins, ions etc
• moisten chime arriving from stomach
• maintain digestive material in solution
• mixes food with pancreatic and biliary secretions

Question 2

duodenum

Answer 2

-secretes HCO3- rich mucus
-bile/pancreatic juices enter via ampulla of Vater
-continues process of chemical digestion
-12 inches

Question 3

jejunum

Answer 3

-4-7ft
-secretes additional digestive enzymes
-completes chemical breakdown of food

Question 4

ileum

Answer 4

-7-15ft
-absorption
-bile also absorbed here

Question 5

mesentery

Answer 5

blood to and from the SI

Question 6

secretions of the SI

Answer 6

-H2O - large quantities secreted
-almost all reabsorbed
-alkaline solution: HCO3-, Na+, Cl-
-> neutralise gastric acid
provide correct pH for digestive enzymes + micelle formation
prevent duodenal ulcers
-mucus
-digestive enzymes - succus entericus
-hormones - CCK, secretin

Question 7

hormonal secretions of the SI

Answer 7

from endocrine cells in the duodenum
SECRETIN:
-DECREASE gastric HCl secretion
-INCREASE intestinal, pancreatic + biliary HCO3- secretions

CCK
-inhibits gastric emptying
-INCREASES bile secretion - fat absorption
-INCREASES secretion of enzyme-rich pancreatic juice

Question 8

what is CCK

Answer 8

cholecystokinin