Flashcards in Unit 6 Deck (27):
When are you histologically within the body?
When you cross the epithelium outside of the digestive system
What are the four main functions of the GI system? Which are the ones that are regulated?
Digestion, absorption, secretion and motility. Secretion and motility are regulated.
What is a fun fact about the GI tract in regards to hormones?
It is the biggest hormone producing place within the body
What re rugae?
Folds within the stomach that allow for stretch
What re the myenteric and submucosal plexuses?
myenteric is the one that innervates the muscle of the gut, and controls motility
The submucosal one controls the secretion that occurs within the gut
What are plicae?
They are the ridges going around within the small intestine. The are NOT for stretch, but are rather. way to increase absorption
What are peristalsis and segmental contractions used for in gut motility?
Peristalsis is used for moving foor from the mouth to the anus and is ONE-WAY movement - it involves contraction of the circular muscle behind a bolus of food and it will move forward
Segmental contractions are for mixing and churning. It maximizes the exposure to the digestive enzymes and the epithelium. The swishing movement is to allow for a better chance for nutrients to be reabsorbed
What happens in the gut between meals? During/after meals?
There are migrating motor complexes that slowly sweep down the tract and are responsible for the ~90 minutes between stomach and large intestine. During meals there is both peristaltic and segmental contractions.
How is the force and duration of muscle contractions related to action potentials?
The duration and intensity of action potentials is directly related to the amplitude and frequency of the action potentials (the are NOT all-or-none). They are related to the amount of Ca that enters as a result of voltage gate Ca channels
What is one of the biggest jobs of the stomach? What is one fo the problems with this job?
to secrete acid. This job requires a lot of energy through DIRECT ACTIVE TRANSPORT
What cells in the stomach secrete acid? What other molecules are transported along with the acid?
Parietal cells. Bicarb is being popped out the back along with the chloride shift and an alkaline shift that is pushing the acid out
How do you keep the mucous from getting too sticky within the small intestine?
You secrete a watery saline. Via a NKCC channel, you bring in Cl all the way into the lumen via a CTFR and the Na and K are reabsorbed. the Na meets up with the H2O and the Cl attracts the Na by the paracellular pathway and the water follows
What are islet cells within the Pancreas?
They are endocrine glands that secrete into capillaries.
What are acinar cells? What do they secrete?
Acinar cells secrete pancreatic enzymes into the pancreatic duct
What do the epithelial cells that line the pancreatic duct secrete?
They secrete bicarb. This is dumped into the duodenum to neutralize the acid that is being brought in from the stomach
What causes cystic fibrosis?
A mutation ion the CFTR channel, and it causes defects in Cl- and water transport. The Cl- is not secreted onto into the lumen of the GI tract and there is therefore no water that follows. As mucous is still produced at the regular rate, it becomes very sticky and thick. There is then a blockage of the pancreatic ducts and the exocrine secretions fo the pancreas is not released (bicarb and pancreatic enzymes) and there is back pressure/inflammation and resultant damage to the pancreas (swelled acing cells and cysts)
What cells produce mucous?
Exocrine glands - serous cells in the salivary glands, mucous cells within the stomach and goblet cells in the intestine
What are the signals to secrete mucous?
Parasympathetic stimulation, various neuropeptides, cytokines (infection or inflammation)
What is the osmolarity of saliva? How does this happen?
It is hypo osmotic. The acini of the salivary glands secrete isosmotic fluid and this passes through the ducts. As this passes though the ducts, the epithelial cells reabsorb the Na and secrete K so the saliva resembles intracellular fluid, and is hyposmotic (more water)
What are some signals for salivary secretion?
Parasympathetic innervation and sympathetic inhibition
What is the point of the gall bladder?
A storage centre for the bile produced by the liver. Rather than relying on a steady drip of bile from the liver, the digestive system can get bursts of bile during
What is cool about the blood supply within the liver?
There is a blood vessel within the middle, and then the blood supply goes out the the corners and down
What is bringing most blood into the liver?
the hepatic portal vein
What is the blood flow of the liver?
~25% of the blood comes from the hepatic artery,adn ~75% of the blood comes from the hepatic portal vein from the GI tract, and the spleen. These go into the sinusoids of the liver , where the liver takes up most nutrients that were reabsorbed by the GI tract.
What is bilirubin?
A break down product of hemoglobin. It is an indicator of injury and pathology (yellow of bruises and jaundice
What are some common components of bile?
Bile salts, bile pigments, and cortisol