GI Part 2

salivary amylase

digestion of carbohydrates in the mouth is done by

pancreatic amylase

digestion of polysaccharides to disaccharides and glucose in the small intestine

brush border enzymes

Digestion of disaccharides to glucose in the small intestine

large intestine

Fiberous carbs are digested where

water, gas, short-chain fatty acids

Fermentation of viscous fibers by bacteria produces

fructose

A patient presents to the clinic with a genetic defect, they have no GLUT transporters in their small intestines, which molecule is not able to be absorbed

glucose and galactose

absorb by being coupled to Na+ and SGLT

small intestine

absorption of proteins takes place in the

pepsin

With in the stomach, ________ breaks down proteins into fragments

chief cells

Pepsinogen is produced where?

HCl from parietal cells

Pepsinogen is activated by

Trypsin, chymotrypsin

Which pancreatic enzymes digest peptide fragments into small pieces that may be absorbed?

carboxypeptidase

Which pancreatic enzyme digest peptide fragments into amino acids?

aminopeptidase

Which brush border enzyme digest peptide fragments into amino acids?

secondary active transport (coupled to Na+)

Amino acids are absorbed into the cell via

transcytosis, facilitated diffusion out of the cell, enter the capillary via intercellular clefts

What happens after the amino acid enters the cell

pancreatic lipase

What is the major enzyme of fat digestion?

mechanical disruption (specifically retropulsion and segmentation)

What is the role of motility in the digestion of fats?

bile salts, phospholipids

What can act as an emulsion agent in fat digetion?

repel other lipid droplets, increases potential surface area

Why does the binding of bile salts and phospholipids assist in fat digest?

impairs the physical access to the droplets

How does the binding of an emulsion agent hinder the action of pancreatic lipase?

binds lipase to the droplet (wingman)

What is the role of colipase?

micelles

act as free-lipid storage

fat globule, emulsion droplet, free fatty acids, micelle

order of fat breakdown

convert to triglycerides in the smooth ER

What happens when the free fatty get into the cell?

maintain diffusion gradient

What is the purpose converting the free fatty acids we worked so hard to get back into triglyerides?

phospholipids, cholesterol, and ADEK

Triglycerides droplets in the cell contain?

chylomicrons

Triglycerides are released into ECF as

chylomicrons are absorbed by lacteals, thoracic duct, left venous angle

How does fat reach the circulatory system?

diffusion as micelles breakdown

The ADEK vitamins are absorbed by?

Parietal cells secrete intrinsic factor which is needed for the absorption of B12

A patient presents to the ER for fatigue and dizziness, CBC shows low hemoglobin and high MCV. The patient reports that she takes a daily multi-vitamin that includes B12. What cell type could be the issue and why?

Ileum

the B12-intrinsic factor complex is absorbed in the

diffusion or mediated transported

How are water soluble vitamins ( except B12) absorbed?

active transport of Na+ and glucose

How is water absorbed in the GI tract?

A high TBIC means low ferritin (low iron)

A patient reports to the ER for shortness of breath, dizziness, and weakness. CBC shows low Hemoglobin and low MCV. If you ran further labs to determine total iron binding capacity, what could that tell you?

active transport

How is iron absorbed in the body?

ferritin

What is the intracellular iron storage unit?

free Fe

What is the metabolically active form of iron?

increase to decrease the amount of free Fe

After eating an Iron rich meal of steak and kale, what could you expect to happen to your ferritin levels?

short reflexes

The enteric nervous system relies on

long reflexes

The CNS relies on ______ in the GI tract

submucosal plexus and myenteric plexus

What makes up the enteric nerve plexuses

secretory activity

A patient presents to the ER with a history of worsening GI ulcers, theoretically if the ulcer reached the submucusal plexus what would be affected?

smooth muscle activity

The myenteric plexus controls

short (luminal stimulant)

A change in the acidity of the chyme would have what type of reflex

distention, chyme osmolarity, chyme acidity, chyme concentration

Luminal stimulant types

rest/digest, thoughts of food, sight, smell, taste

Long reflexes include

enteroendocrine cells

Which type of cells respond to luminal stimulants?

gastrin

What are the hormones of the gastric phase?

CCK, secretin, GIP

What are the hormones of the intestinal phase?

CCK, secretin

which two hormones decrease the motility and the H+ production of the stomach (aka bully the stomach)?

increase stomach acid secretion and motility

What is the role of gastrin in the gastric phase of digestion?

increasing the pH, stimulating gastrin release

An increase of proteins in the stomach is going to have what effect?

inhibited by a low pH so we don’t digest our ownselves

Why is the inhibition of gastrin a protective function?

secretin release, increased bicarb secretion

A decrease in pH in the intestine is going to have what effect?

CCK

Which hormone is responsible for getting bile into the GI tract?

fatty acids and amino acids in the small intestine

How is CCK stimulated?

the removal of fatty acids and amino acids from the small intestine

What is the negative feedback for CCK release?

voluntary and involuntary

Chewing sends a efferent signal to skeletal muscles that is

saliva production

the sight and smell of food and chemical/pressure receptors in mouth and on the tongue triggers what response?

sympathetic and parasympathetic

saliva production is controlled by

medulla oblongata

Where is the swallowing reflex coordinated?

increase production of ACh, Histamine, gastrin, and stomach relaxes

How does the cephalic phase affect the stomach

increase proton pumps

How do we lower the pH of the stomach?

parasympathetic CNS stimulates ACh

How does the CNS contribute to HCL regulation

actively transporting H out and K in; coupling Cl- in and bicarb out

How do we maintain membrane potential of the parietal cells if we have so many proton pumps?

bolus becomes chyme

Gastric phase of digestion starts when

stomach distention, presence of peptides

H+ secretion is promoted by

elevated gastrin, stomach’s distention

the forcefulness of the contractions by the antrum is increased by

enterogastric reflex (duodenal distention, presence of fat, low pH, hypertonic solutions in duodenum)

antral contractions and gastric emptying are slowed by the

CCK, secretin

The enterogastric reflex stimulates what hormones?

decrease parasympathetic, increase sympathetic

What is the long reflex for the enterogastric reflex?

Cephalic

What phase uses the vagus nerve to activate the GI tract