GI/Liver Recap Flashcards
Explain the basic/main physiologic functions of the esophagus
Muscular tube to move oral contents into stomach
Receives lubrication from oral cavity
Explain the basic/main physiologic functions of the stomach
Chemical breakdown of food via HCl and pepsin (+ small amount of lipase)- this also help to partially sterilize the meal
Physical breakdown of food via gastric motility patterns (mixing and grinding)
Controls release/rate of delivery of meal to the intestines
Explain the basic/main physiologic functions of the duodenum
Site of emptying for products of the pancreas and gall bladder for further digestion
“Monitors” the characteristics of the meal to prepare the later GI tract (and negative feedback back to stomach)
Explain the basic/main physiologic functions of the pancreas (exocrine only)
Secretes digestive enzymes for a mixed meal (fat, protein, carb)
Amylase (Carb), Lipase (Fat), Proteases- trypsin and chymotrypsin (protein)
Also secretes large amount of bicarbonate to neutralize acid coming from stomach
Explain the basic/main physiologic functions of the jejunum
Majority of nutrient absorption- very high surface area
Helps with electrolyte balance
Peristalsis patterns to move food aborally
Explain the basic/main physiologic functions of the ileum
Some nutrient absorption but less compared to jejunum
Major site of B12 and bile salt/bile acid absorption
Explain the basic/main physiologic functions of the colon
Major site of water reabsorption- goal is to retain contents long enough for water to be absorbed
Large numbers of bacteria- fermentation and some nutrient production/modification
Storage reservoir for waste
What are the clinical signs of small bowel diarrhea?
Large volume of feces
Normal or increased frequency
Flatulence, steatorrhea
Melena (tarry, black)
Weight loss
Vomiting may occur
What are the clinical signs of large bowel diarrhea?
Small volume of feces
Increased frequency
Mucus in feces
Hematochezia
Tenesmus
Pain or urgency to defecate
What is enterohepatic recirculation and why do we care about it?
Products that are filtered by the liver and excreted into bile go into the small intestine, where they are absorbed by the enterocytes and are transported back into the liver.
One bile salt can be re-used about 20 times.
This can prolong the activity of drugs/toxins (particularly lipophilic ones) and lead to repeated damage to the liver or ongoing high blood levels.
What are the zones of hepatocytes? How does this apply to histopathology when trying to determine the cause of liver damage?
- Zone 1 (periportal cells)- closest to the portal vein
— Responsible for the majority of detoxification and secretory functions under normal circumstances - Zone 2- middle
- Zone 3- closest to the hepatic vein
— Can be recruited if liver function is compromised
Zonation also impacts susceptibility to injury
—- Zone 3 hepatocytes most sensitive to hypoxia if blood supply is compromised
—- Zone 1 hepatocytes most affected by oxidant injury from reperfusion injury or toxins
Explain Phase 1 hepatic conjugation reactions/ how the liver metabolizes drugs.
- Chemically changes drug so more water soluble 🡪 more susceptible to phase II metabolism
- Oxidation, hydrolysis (addition of water), reduction (addition of hydrogen) can occur
- Cytochrome P450 enzymes are responsible for the majority of phase I metabolism
- Phase I metabolites are usually inactive (but can be equally, more, or less active or more toxic than the parent compound)
—- Can be an important source of drug-induced toxicity
Explain Phase 1 hepatic conjugation reactions/ how the liver metabolizes drugs.
- = conjugation– large water-soluble molecule is chemically added to the phase I metabolite or the parent drug 🡪 usually renders drug sufficiently water soluble to be renally excreted
- Most phase II reactions require energy
- Glucuronidation is the most common phase II reaction
- Sulfonation, acetylation, and addition of glutathione are less common phase II reactions
- Phase II metabolites are almost always inactive and are often eliminated in the urine
Draw/label the bile ducts from liver to duodenum.
Explain the basics of the ammonia/urea cycle
Ammonia (NH3) is produced from AA degradation, mostly in intestines. Most Ammonia is absorbed into portal circulation and brought to the liver. Small amount of ammonia is “protonated” to ammonium ion (NH4), which is trapped in the colon and eliminated in the stool.
In the liver, ammonia is taken up by hepatocytes and enters mitochondria where it is converted to urea. Urea then enters circulation and is excreted by kidneys into the urine.