Lecture 20: BASIC STRUCTURE OF THE GI SYSTEM Flashcards
What is the primary function of the GI system?
Bring nutrients into the internal environment (blood) so that they can be used for growth and energy. Waste is excreted
What functions is the GI system specialised for?
Motility, secretion, digestion and absorption
What are the key structures of the GI system?
Long tube with outgrowths, closed off at both ends, lined by epithelium
How is the GI system closed off at both ends?
Sphincters - thickened regions of circular smooth muscle
Why is the GI system lined by epithelium?
Because it is exposed to the outside
Where in the GI system is there stratified squamous epithelium?
Mouth/oral cavity, oesophagus, anal canal
What is the purpose of stratified squamous epithelium?
Protection from abrasion
Where in the GI system is there simple columnar epithelium?
Stomach, small intestine and large intestine
What is the purpose of simple columnar epithelium?
Secretion and absorption
What are unicellular glands?
Goblet cells
What is the shape of goblet cells?
Columnar, goblet
What is on the apical side of goblet cells?
Mucous granules
What is on the basal side of goblet cells?
Nucleus and other organelles because the mucous granules push them down
What can the epithelium do?
Invaginate to form glands
What are the types of multicellular glands?
Simple and compound
What are simple glands?
Gland with a single duct
What are compound glands?
Gland with two or more ducts, have more surface area for secretion
What are the layers of the gut (from inner to outer)?
Mucosa, submucosa, muscular (externa/proper) and adventitia
What is in the mucosa?
Epithelium, lamina propria (FCT), muscularis mucosa and sometimes glands
What is between the epithelium and lamina propria?
Basement membrane
What does the lamina propria of the mucosa contain?
Blood vessels and lymphatics
What is the muscular mucosa?
Thin layer of smooth muscle
What is in the submucosa?
Glands and blood vessels
How is secretion in the submucosa regulated?
By the submucosal nerve plexus which is part of the enteric nervous system (ENS)
What is the ENS?
The nervous system of the gut which can work independently of the CNS