Unit 6

Question 1

When are you histologically within the body?

Answer 1

When you cross the epithelium outside of the digestive system

Question 2

What are the four main functions of the GI system? Which are the ones that are regulated?

Answer 2

Digestion, absorption, secretion and motility. Secretion and motility are regulated.

Question 3

What is a fun fact about the GI tract in regards to hormones?

Answer 3

It is the biggest hormone producing place within the body

Question 4

What re rugae?

Answer 4

Folds within the stomach that allow for stretch

Question 5

What re the myenteric and submucosal plexuses?

Answer 5

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

Question 6

What are plicae?

Answer 6

They are the ridges going around within the small intestine. The are NOT for stretch, but are rather. way to increase absorption

Question 7

What are peristalsis and segmental contractions used for in gut motility?

Answer 7

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

Question 8

What happens in the gut between meals? During/after meals?

Answer 8

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.

Question 9

How is the force and duration of muscle contractions related to action potentials?

Answer 9

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

Question 10

What is one of the biggest jobs of the stomach? What is one fo the problems with this job?

Answer 10

to secrete acid. This job requires a lot of energy through DIRECT ACTIVE TRANSPORT

Question 11

What cells in the stomach secrete acid? What other molecules are transported along with the acid?

Answer 11

Parietal cells. Bicarb is being popped out the back along with the chloride shift and an alkaline shift that is pushing the acid out

Question 12

How do you keep the mucous from getting too sticky within the small intestine?

Answer 12

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

Question 13

What are islet cells within the Pancreas?

Answer 13

They are endocrine glands that secrete into capillaries.

Question 14

What are acinar cells? What do they secrete?

Answer 14

Acinar cells secrete pancreatic enzymes into the pancreatic duct

Question 15

What do the epithelial cells that line the pancreatic duct secrete?

Answer 15

They secrete bicarb. This is dumped into the duodenum to neutralize the acid that is being brought in from the stomach

Question 16

What causes cystic fibrosis?

Answer 16

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)

Question 17

What cells produce mucous?

Answer 17

Exocrine glands - serous cells in the salivary glands, mucous cells within the stomach and goblet cells in the intestine

Question 18

What are the signals to secrete mucous?

Answer 18

Parasympathetic stimulation, various neuropeptides, cytokines (infection or inflammation)

Question 19

What is the osmolarity of saliva? How does this happen?

Answer 19

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)

Question 20

What are some signals for salivary secretion?

Answer 20

Parasympathetic innervation and sympathetic inhibition

Question 21

What is the point of the gall bladder?

Answer 21

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

Question 22

What is cool about the blood supply within the liver?

Answer 22

There is a blood vessel within the middle, and then the blood supply goes out the the corners and down

Question 23

What is bringing most blood into the liver?

Answer 23

the hepatic portal vein

Question 24

What is the blood flow of the liver?

Answer 24

~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.

Question 25

What is bilirubin?

Answer 25

A break down product of hemoglobin. It is an indicator of injury and pathology (yellow of bruises and jaundice

Question 26

What are some common components of bile?

Answer 26

Bile salts, bile pigments, and cortisol

Question 27

What is needed to reabsorb carbohydrates?

Answer 27

A membrane transporter, but we only have membrane transporters for monosaccharides. So the job on digestion is to make monosaccharides