文档介绍：Chapter 6
Digestion & Absorption
Introduction
Concepts of digestion and absorption
Characteristics of the smooth muscle of
gastrointestinal tract
Secretory function of digestive gland
Neural control of gastrointestinal tract
Endocrine function of gastrointestinal tract
ĉĉĉ. Concepts of digestion and absorption
The main types of foods
Carbohydrads, fat , protein large molecules
Vitamine, anic salt, water small
molecules
Fiber— promote motility of GI
Digestion:
The breakdown of proteins, fats and carbohydrates
into absorbable molecules in the gastrointestinal tract .
Protein amino acid
Carbohydrate haride
Fat fatty acid and glycerol
Absorption:
The movement of the digested products ,water and
electrolytes from the lumen of digestive tract into the
lymph or the blood .
closed relationship between digestion and absorption
How are the foodstuffs digested ?
Structure of digestive system
Digestive tract: mouth, esophagus, stomach,
intestine and anus
Large ~: salivary gland ,liver
Digestive glands: pancreas
Small ~: gastric glands ,
intestinal glands
Mechanical Digestion:
The motility of smooth muscle in gastrointestinal
tract grinds food and mixes it with digestive
juice to prepare it for chemical digestion and
absorption, and then propels the food
along the gastrointestinal tract.
Chemical Digestion:
Nutrients in the food are broken down by the
digestive juice secreted by the secretory
glands.
of Gastrointestinal
Smooth Muscle
1. General physiological characteristics
‹low excitibility
Vslow contractility
‹high extensibility
‹tonicity
‹Sensitive for chemical,thermal and
mechanical stretch stimulation
2. Electrophysiological characteristics
resting membrane potential
slow wave potential
action potential
RestingResting potentialpotential ofof smoothsmooth musclemuscle ININ GIGI
Value: -50 -60mV
Formation:
out flow of K+ ; Na + Cl - Ca 2+
electrogenic