exercise 39a digestive physiology. the digestive process ingestion propulsion mechanical...
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Exercise 39A
Digestive Physiology
The Digestive Process
IngestionPropulsionMechanical DigestionChemical DigestionAbsorptionDefecation
Motility vs. MixingThe difference between peristalsis and segmentation:
Peristalsis moves food along the tract. Segmentation is mixing and part of the mechanical digestion
process.
Absorption of Nutrients• Nearly all occurs in the small intestine.
– 80% of the electrolytes and virtually all food
• Most nutrients are absorbed by active transport.– Glucose, amino acids, & nucleic acids are absorbed
by secondary active transport with sodium.– Iron and calcium require transport proteins (ferritin) or
cofactors (vitamin D).– Anions follow Na+.
• Vitamins -– Fat soluble (A, D, E & K) vitamins are carried with
micelles. Much of the K is absorbed in the colon.– Water soluble vitamins diffuse with the exception of
B12, which requires intrinsic factor.
Hormonal regulation of bile release
Exocrine tissues of the pancreas
Activation of pancreatic proteases in the duodenum
Regulatory mechanisms for release of pancreatic juice
Chemical Digestion Carbohydrates & proteins
Chemical Digestion Lipids & Nucleic acids
Protein digestion in the small intestine
Bile salts emulsify fats
Absorption of lipid
Dietary fats are absorbed into the “lacteals” of the lymphatic system before being transferred to the circulatory system.
Lacteals
The End