Gastrointestinal System (Motility) Flashcards
What does the GI tract do?
Th GI tract takes in food, digests it to extract and absorb metabolities for the growth and energy needs of the body plus fluid and electrolytes to replace losses, and expel the remaining waste.
What does the GI system consist of?
A long epitehlium lined tube - with functional secretions seperated by sphincters and connected to accessory exocrine glands.
mouth
pharynx
esophagus
stomach
large intestine
small intestine
anus
What are the three sections of the small intestine?
Duodenum
Jejunum
llium
What are the sphincters of the GI tract?
Upper esophageal sphincter
Lower esophageal spincter
Pyloric sphincter
Sphincter of Oddi (or hepatopancreatic sphincter)
Illeocecal valve
Anal sphincter (internal and external)
What are the salivary glands of the GI tract?
Parotid salivary glands
Sublingial salivary glands
Submandibular salivary glands
What are the accessory exocrine glands of the GI tract?
Salivary glands
Pancreas
Liver
Gall bladder
What are the 4 layers of the GI tract wall?
Mucosal layer
Sub-mucosal layer
Muscularis layer
Serosal layer
What are the two secretoary glands of GI tract wall?
intestinal glands
Submucosal gland
What are the two seperate layers of the muscular layer of GI tract wall?
Circular (inner) and longitudinal (outer) layer
What are the components of the mucosa?
Epithelium
Villi
Lamina Propria
Muscularis mucosae
What are the components of the sub-mucosal layer (the supporting mucosa layer)?
Submucosal plexus, connective tissue blood vessels
What layer of the GI tract wall si the myenteric plexus located in?
Muscularis layer
What is a plexus?
Network of vessels and nerves (layer of neurons)
What is the serosal layer?
The outer sheath of the GI tract wall
What are GI reflexes initiated and senses by?
Stretch = mechanoreceptors
Chemical compositon of luminal contents = osmoreceptors
Concentration of products of digestion in the chyme = chemoreceptors
What is chyme?
Semi-fluid mass of partly digested food
What are the signal pathways of the GI tract?
Neural = CNS and ENS
Hormonal
What are the effectors of the GI tract?
GIT smooth muscle (motility)
Epithelial cells (secretion and absorption of the luminal content)
What are the phases of GI regulation?
1) cephalic phase
2) gastric phase
3) intestinal phase
What is the cephalic phase?
Preparative phase - it prepares the stomach for the arrival of food.
Prepares the GIT lumen by initiating CNS via ENS
What is the cephalic phase stimulated by?
Sensory stimuli: The sight, smell, taste and swallowing of food
Explain how the cephalic phase prepares the stomach:
Inhibits muscles in the proximal stomach (Receptive relaxation)
Triggers low level stimulation of antral contraction by modulation of ENS (antrum = lowest part of the stomach)
Stimulates the release of gastrin from G cells
Starts the regulation of gastric secretion
Is the pyloric sphincter opened or closed during the cephalic phase?
Closed
What is the gastric phase?
The digestive phase in the stomach