The Digestive System Flashcards
What are the two major functions of GIT?
Digestion and absorption
What is digestion?
Breakdown of complex food materials to smaller absorbable forms
What is absorption?
A process of passing the products of digestion, water, vitamins and minerals to the blood
What do the functions of the GIT need?
The secretion of digestive enzymes and gastrointestinal hormones
Coordinated movements (motility) of different parts of the digestive tract
What is motility needed for?
Mix food with the digestive enzymes
Push food along GIT from the mouth towards anus
The secretion and motility are controlled by what?
Nervous mechanism → the enteric nervous system
hormonal mechanism → the enteroendocrine system
What is the enteric nervous system?
Local nervous system of the digestive system, that is composed of two plexuses of neurons, both of which are embedded in the wall of the digestive tract and extend from the esophagus to the anus
What are the two plexuses of the ENS ?
The subermacous (Meissener’s) plexus
The myenteric ( Auerbach’s ) plexus
What is The subermacous (Meissener’s) plexus?
It is buried in the submucosa
It’s principal role is: sensory, regulation of gastrointestinal blood flow, control of secretions from epithelial cells
What is The myenteric ( Auerbach’s ) plexus?
Located between the outer longitudinal and the inner circular muscle layers
Controls the digestive tract motility
What does the enteric neurons secrete?
Neurotransmitters → acetylcholine and norepinephrine
What does acetylcholine do?
Stimulates smooth muscle contraction, increases intestinal secretions, releases enteric hormones and dilates the blood vessels
What does norepinephrine do?
It’s inhibitory, so its actions are opposite to that of acetylcholine
What does the sympathetic stimulation do?
Inhibits both gastrointestinal secretion and motor activity, but it is motor to the sphincters causing food retention
What does the parasympathetic stimuli do?
Stimulates the digestive activities
