Small Intestine Flashcards
What are the functions of the duodenum
Gastric acid neutralisation, digestion, iron absorption
Function of jejunum
95% nutrient absorption
Ileum function?
NaCl/H2O absorption = Chyme dehydration
What do crypt cells secrete
Cl and H20
How do substances leave lumen to blood
through Na+-coupled secondary active transport
How is h2o secreted into lumen
Passively following active transport of cl into lumen
What does water do in digestion
- Maintains lumenal contents in liquid states
- Promotes mixing of nutrients with digestive enzymes
- Aids nutrient presentation to absorbing surface
- Dilutes and washes away potential injurious substances
Review slide 9**
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two types of intestinal movement :
Peristalsis and segmentation
What happens during meal
segmentation
how does segmentation happen
initiated by depolarisation by pacemaker cells in longitudinal muscle layer) =>
Intestinal basic electrical rhythm produces oscillations in membrane potential => AP induced => contarction
What determines strength and frequency of contraction
Strength : Frequency of AP
Frequency of segmentation : Determined by BER
What is the migrating motility complex
Pattern of peristaltic activity travelling down small intestine (starts in gastric antrum)
MMC acts to:
- Move undigested material into small intestine
2. Limit bacterial colonisation of small intestine
What hormone involved in initiation of mmc
Motilin
What nerve supply controls movement of muscle in intestine to move blous to colon
Neurones in myenteric plexus
What is the gastroileal reflex
Entry of chyme into large inestine causes distention of colon and as a result the ileocaecal sphincter closes to prevent reflux of material
