文档介绍：Chapter 6 Digestion and Absorption
The gastrointestinal(GI) system consists of the gastrointestinal tract and accessory glands.
GI tract: posed of mouth, pharynx, esophagus, stomach, small intestine, colon, rectum and anus.
Accessory glands: posed of salivary glands, pancreas, liver, and so on.
Section 1 Introduction
(1)Definition: In gastrointestinal tract, the food was hydrolyzed into small, and simple substances. This dissolving and breaking-down process is called digestion.
(2)Manners of digestion:
(i)Mechanical digestion: Grind and mix food and digestive liquid; Push food into far end of tract.
(ii)Chemical digestion: the action of hydrocholoride acid in the stomach, bile from the liver, and a variety of digestive enzymes.
: the process of transporting small molecules from the lumen of the GI tract into blood.
ⅠCharacteristics of smooth muscle in GI tract
mon properties:
(1)Low excitability.
(2)Rhythmic tonus.
(3)Tonic contraction.
(4)Bigger extensibility.
(5)Sensitive to chemical, stretch stimuli, not to voltage(electrical stimulus).
2. Bioelectrical Properties
(1)Resting potential:
-50mv~-60mv, K+ outflow, or Na+-K+ pump activity.
Threshold potential: -40mv
(2)Slow wave: basic electrical rhythm (BER): it is a kind of waves of spontaneous, slow and recurring depolarization based on RP.
Intensify: 10-15mv
Frequency: 3-12