Flashcards in GIT Form and Function Deck (19):
Functions of the GIT
Ingestion of food, excretion of waste, secretions of fluid and digestive enzymes, mixing and movement of food and waste around the body, absorption of nutrients, digestion of food into smaller pieces
How long is the gut?
What are the characteristics of a hormone?
- release of a hormone causes a physiological change
- has a target
- travels in the blood
- must be able to be identifies and has the same effect exogenously
- effect remove after the removal of a neural input
What are goblet cells?
Cells that secrete mucus which protect the gut from acid in the stomach
Blood supply of the gut
70% of blood flow from the gut will go to the liver before the heart via the vena cavae. This is so toxins are removed from the blood and the hepatic portal vein is a site of nutrient sensing
What is an endocrine mechanism?
Has a sensor cell that has microvilli that project into the lumen of the gut, these sense triggers and release hormone into the blood to a target cells where it acts on the receptors and causes a physiological change.
What is a paracrine mechanism?
Has a sensor cell that has microvilli that project into the lumen of the gut, a paracrine mediator is released into the extracellular space, effecting target cells in its immediate vicinity.
What is the serosa layer of the gut?
External layer of the gut, a couple of cells thick, acts a lubricating layer, things can easily slide over the surface of the gut.
What is the muscularis externae layer of the gut?
External muscle layer, comprises of circular and longitudinal muscle.
Contraction of longitudinal muscle, shortens the gut.
Contraction of circular muscle, narrows the lumen.
What is the myenteric plexus of the gut?
Lies between the circular and longitudinal muscle layers. It is the major nerve supply of the GIT and controls motility. Has both parasympathetic and sympathetic inputs
What is the submucosal plexus of the gut?
Lies in between the submucosa and circular muscle, it has only parasympathetic fibers and provides secretomotor innervation to the mucosa nearest the lumen of the gut..
What is the submucosa layer of the gut?
Layer of connective tissue, containing glans, lymph nodes, major nerves and blood supply
What are the 3 components of the mucosa layer?
- Epithelium - single layer of cells for absorption, contains villus
- Lamina propria - mainly connective tissue, lymph nodes, blood supply and nerves
- Muscularis mucosa - thin muscle layer controlling the rest of the mucosa layers
What are the 3 peptidergic mechanisms?
1. Endorine - sensor cells detect substrate/stimuli and causes the activation of the cell and the release of hormone into the circulation, which then modulates a distant cell at a target site. modulates distant sites and large areas of the GIT
2. Paracine - sensor cell detects substrate/stimuli causing release of the paracrine mediator into the extraceullar space and modulates target cells close to the sensor cell
3. Neurocrine - sensory neurone which synapses onto an interneurone, which then synapses onto a secretomotor neurone, modulator is release from the synaptic cleft to modulate cell. Can have a focused or distant effects.
What cells are peptides released from?
APUD cells - amine precursor uptake decarboxylation cells, which are distributed on the epithelial cells of the GIT.
Where is gastrin released from?
Crypts of Lubricant, crypts in the antrum and duodenum
What are the two forms of gastrin?
G17 and G34 - before acid secretions, more G34 is released than G17. G34 is G17 plus other amino acids
What are normal calcium levels in the blood?