Small Intestine Structure and Function Flashcards
What does the small intestine consist of ?
The duodenum, the jejunum and the ileum
What occurs in the duodenum/jejunum and the ileum ?
Duodenum: Gastric acid neutralisation; Digestion;Iron absorption.
Jejunum: Nutrient absorption
Ileum: NaCl/H2O absorption and chyme dehydration
What enhances the absorptive ability of the small intestine ?
By folds, villi and microvilli increasing the surface area.
What occurs within the crypts of the small intestine ?
Secrete water
How much water is secreted by the small intestine daily ?
1500ml
What is present on the brush border that allows the passage of Cl ions ?
CFTR channels
What are the 2 types of movement in intestinal mobility ?
Segmentation
Peristalsis
What is the most common form of intestinal motility during a meal and what does this invlolve ?
Segmentation
Contraction and relaxation of short intestinal segments
Following the absorption of nutrients ___ stops and ____begins.
Segmentation
Peristalsis
What is MMC ?
Migrating Motility Complex (MMC)
Pattern of peristaltic activity travelling down the small intestine from the antrum.
MMC acts to…
1: Move digested material into the large intestine
2: Limit bacterial colonisation of the small intestine
What hormone is involved in the initiation of MMC ?
Motilin
Explain the law of the intestine
If the intestinal muscle is distended:
The muscle on the oral side of the bolus contracts
The Muscle on the anal side of the bolus relaxes
Bolus is then moved towards the area of relaxation, i.e. towards the colon.
What is the ‘law of the intestine’ mediated by and where is this found ?
Mediated by neurons in the myenteric plexus which is found between the layers of the muscularis
Explain the gastroileal reflex
Gastric emptying causes increased activity in the ileum which pushes the chyme into the colon
