L8: The small intestine Flashcards
What is the role of the villi/micro villi?
To increase the SA available for interaction with food
Outline the process of Peristalsis
- Circular muscles contract behind bolus whilst circular muscles ahead relax
- Longitudinal muscles ahead of the bolus contract
- Wave of contraction forces the bolus forward
Outline the process of segmentation
Alternate contraction of neighboring segments which churn and fragment the bolus. This allows the contents to mix with the secretions
How often do MMC (migrating motor complexes) arrive?
approx every 90 mins
What stimulates MMCs?
Motilin ( 22 aa peptide secreted by M cells)
What inhibits MMCs?
Feeding
What is the function of MMCs?
It helps to keep the gut clean, prevent refulx and reduce bacterial growth
Hormones are secreted in the small intestine from APUD cells. What is secreted from the following: I cells S cells M cells G cells Pancreatic duct cells Goblet cells
I cells = CCK S cells = Secretin M cells = Motilin G cells= Gastrin Pancreatic duct cells = bicarbonate Goblet cells = Mucus
Endopeptidases cut at what part of a protein chain
Within the protein chain
Exopeptidases cut at which point of a protein chain
Cut at the last peptide bond
Describe the 3 stages of fat digestion.
- Bile salts break lipid droplets increasing SA
- Pancreatic lipase cleave outside fatty acids
- These monoglycerides and fatty acids complex with bile salts and diffuse close to the brush border (delivering their contents) Triglycerides are resynthesised into chylomicra
Where are conjugated bile salts actively absorbed?
Distal ileum
What regulated calcium absorption?
Vit D
List the fat soluble vitamins
A, D, E, K
How is B12 absorbed?
Only when bound to intrinsic factor
