Layers of GI tract Flashcards
How many layers of the GI tract are there?
Four
What are the four layers of the GI tract, from inner to outer?
Mucosa
Submucosa
Muscularis externae
Peritoneum
How many layers of the mucosa are there?
Three
What are the three layers of the mucosa, from inner to outer?
Epithelium
Lamina propria
Muscularis mucosae
What type of epithelium lines the GI tract in the mucosa?
Stratified squamous in oesophagus and distal anus
Simple columnar in between
Why is there stratified squamous epithelium at the oesophagus and anus, but simple columnar in between?
At oesophagus and anus, contents passing through are harder and moving faster
and stratified squamous protects against abrasion
In between, lots of secretion and absorption
What are the functions of the epithelia in the GI tract?
Produces enzymes, for digestion
Produces mucus
Produces hormones, for control of GI tract
Selectively permeable barrier, for absorption
What is the lamina propria made up of?
Loose areolar connective tissue
What does the lamina propria contain in the GI tract?
Lymphoid nodules
Mucous glands
What are the functions of the lymphoid nodules in the lamina propria?
Produce IgA antibody
protects against infection
What are the functions of the muscualris mucosae in the GI tract?
Contracts to shape epithelial layer
to keep epithelial layer in contact with GI tract contents
What is the submucosa made up of?
Dense connective tissue
What does the submucosa contain in the GI tract?
Blood vessels, lymphatics
Nerves, submucosal plexus
Glands
How many layers of the muscularis externae are there?
Two
What are the layers of the muscularis externae?
Inner circular layer
Outer longitudinal layer
How does the inner circulayer layer run around the GI tract?
Runs around the circumference of the GI tract
How does the outer longitudinal layer run around the GI tract?
Runs down the length of the GI tract
What is located between the inner circular layer and outer longitudinal layer?
Myenteric plexus
What is the peritoneum made up of?
Mesothelium
Connective tissue layer
What is the mesothelium made up of?
Simple squamous epithelium
What does the connective tissue of the peritoneum contain?
Blood vessels and nerves
What does the mesothelium do?
Secretes lubricating fluid
What does the connective tissue of the peritoneum do?
Attaches the mesothelium to adjacent tissues
