GI I & II: General Principles of GI Regulation Flashcards
What is the importance of reducing the size of food particles during the motility phase of digestion?
It allows for an increased surface area for chemical digestion by enzymes.
The rate at which food is propelled is regulated to optimize ____________.
the time for digestion and absorption
What are the associated glands of the GI system, and what are they responsible for?
- salivary glands, pancreas, liver, and gallbladder
- they are responsible for producing mucous and secretions and emptying them into the GI tract to aid digestion and absorption
The GI tract excretes which products from the liver?
cholesterol, steroids, drug metabolites
What represents the largest immune organ of the body?
GI tract
Are GI sphincters smooth muscle or skeletal muscle?
they are circular muscle structures, either smooth or skeletal
What is the blood supply of the GI tract? How much blood flow does the GI tract receive?
The blood vessels that supply the GI tract comprise the splanchnic circulation, which receives 25% of our total cardiac output.
What are the 3 major arteries that supply the abdominal organs?
- celiac artery (liver, spleen, stomach)
- SMA (pancreas, small intestine, proximal colon)
- IMA (distal colon)
Does the venous drainage from the GI tract return directly to the heart?
No! The venous blood from the abdominal organs flows to the liver first via the portal vein (portal circulation). Blood from the liver is then transported via hepatic veins to the IVC.
Why is lymphatic drainage important for in the GI tract?
transport of lipids and lipid-soluble molecules (including certain vitamins and drugs), which are too large to enter capillaries and pass into lymph vessels; they are then drained via thoracic duct into systemic circulation
The nature of mucosal epithelium varies according to ________.
function
What is the lifespan of the epithelial lining of the GI tract?
3-5 days (epithelial lining is continuously renewed w/ cells at the villus tip shedding every 3-5 days)
Where are proliferative cells located that help to replenish the epithelial lining?
they are localized in crypts
Describe the epithelium of the mucosal layer.
It is a single, continuous layer of specialized cells lining the lumen of the entire GI tract (innermost layer) and interconnected via tight junctions.
What is the most abundant cell type of the mucosal epithelium?
absorptive enterocytes (play a vital role in digestion and absorption)
The surface of small intestinal epithelium consists of which structures, and what is their purpose?
villi and crypts, which are fingerlike projections that help to increase surface area for absorption and also harbor the intestinal stem cells, which help replenish the epithelial lining
What is the difference between esophageal and intestinal epithelium?
Esophageal epithelium helps in transportation of swallowed food (squamous type), while intestinal epithelium helps in absorption or selective uptake of nutrients, ions, and water (columnar type)
The unit of absorption of intestinal cells:
villus
Epithelial cells on the surface of a villus have numerous cytoplasmic extensions at the luminal surface, called _______.
microvilli, or brush border
The mucosal folds, villi, and microvilli increase the SA of the small intestine by how much?
~600 fold
What is the implication of reduced surface area in the small intestine?
malabsorption, which is implicated in celiac disease
What is the main thing to note about the lamina propria (and in which layer is it located?)
- It is rich in glands, as well as lymph vessels and nodes, capillaries, and nerve fibers
- It is part of the mucosa