Ch.35 Jejunum and Ileum Flashcards
Length of small intestine
10 - 30 meters average 25m
Length of jejunum
17 - 28 meters
Where is the jejunum located
Left dorsal abdomen between loops of SC
Arterial supply of jejunum
Cranial mesenteric artery
Major jejunal artery ->arcuate vessel forms a loop with next major jejunal vessel
Vasa recta -> from arcuate vessel to intestinal wall
Venous drainage
Portal v
Length of ileum
0.7 meters
Arterial supply to ileum
Ileal artery a branch from the iliocecocolic artery -off of cranial mesenteric
Travels along ileum -> anastomoses with last jejunal artery
Describe the 3 layers of muscle of the ileocecal papilla
- Inner circular
- Central longitudinal layer from ileum
- Outer from circular m of cecum
arranged into semi circular lips
When does the true ileocecal sphincter contract
In sync with contractions of the cecal base
Where does digestion and absorption of nutrients take place
Upper half of the small intestine
What surrounds each villus
6-9 crypts of Lieberkuhn
Describe the mucosal folds and place circulates in the small intestine
Ha doesn’t have any
What makes up 90% of the small intestine epithelial cells
Columnar absorptive cells or enterocytes
What makes up the remaining 10% of small intestine epithelial cells
Mucous (goblet) cells
Enteroendocrine cells
Paneth cells
Undifferentiated columnar cells
Describe the activity of the columnar cells of the villi
After 2 divisions in the crypt they move to the villus as adult absorptive cells
Eventually extruded at the villi tip
Turnover time of 2-3 days
How is the apical surface of mature enterocytes arranged
In to Microvilli - form a brush border membrane
Where are the enzymes of digestion of carbs, proteins and specific transport systems for absorbing end products located
In the microvilli
How are the pancreas and liver stimulated to secrete bicarb and water
hydrogen ions in the duodenum -> release of secretin from S-cells in the duodenal mucosa
Protein and fat in the duodenum stimulate the release of what
CCK - Cholecystokinin from I-cells in the duodenal mucosa
Effect of CCK release from the duodenal mucosa
Causes Pancreas to secrete
1. Amylase (carbs)
- Lipase (fat)
- Trypsin, chemotrypsin,
carboxypeptidase, elastic (protein) - Co-lipase (coenzymes)
How is Tripsinogen production integral to digestion
Tripsinogne is precursor (zymogen) to trypsin
Trypsinogen needs to reach SI to be activated to Trypsin by brush border enzyme enterokinase
Other enzymes secreted as zymogens can only be activated by trypsin
What volume of enzymatic secretion are produced by horses
10-12L/100kg BW per day
What uniquely has a marked secretory response on the pancreas in horses
Gastrin
What is the main inorganic anion in the horse’s pancreatic secretions
Cl-
Some starch fermentation in horses uniquely occurs where
Stomach and SI
Almost complete digestion of starch from what food source occurs in the small intestine
oats and wheat
What forms conjugated bile salts
Cholic acid & Chenodeoxycolic acid
combine with
Glycine & Taurine
What are bile salts required for in the SI
Emulsification of fat
Describe enterohepatic circulation of bile
94% of bile salts are absorbed in the SI pass to the liver and are re-secreted
Where are bile salts at their highest concentration
Prox jejunum
Where in the SI is most water absorbed
Distal 1/3
What is solvent drag
Water movement from lumen into plasma through cell will drag permeant ions - sugars, amino acids, Ca2+ and Mg2+ with it.
