4B A&P and Pathology of the Small Intestine (Part 2) Flashcards
What is emulsification?
Taking big globules of fat and dispersing them into smaller droplets
What is responsible for emulsification?
Bile
What is the benefit of emulsification?
Increasing surface area of exposed of fat
After emulsification, which two pancreatic enzymes begin digestion on the emulsified fat droplets?
Pancreatic lipase and his friend colipase
What are micelles?
Lipids coated with bile acids to protect and sequester it from water, so the lipids could travel thru the water
Where do micelles go after they form?
To the brush border
How do the micelles get inside the brush border cells?
They merge with the phospholipid bilayer of the brushborder and the fatty contents are uptaken into the inside of the absorptive enterocyte
What happens to the fatty products brought into the cells from the micelles?
Inside they cell they get repackaged with protein-coated chylomicrons
What happens to the chylomicrons?
They go to the lymph vessels - lacteals (lymphatic capillaries) first, then thoracic ducts before going into the blood when the lymph empties into the subclavian veins
Which is bigger lacteals or blood capillaries?
Lacteals (lymphatic capillaries)
Where does the thoracic duct empty into the venous circulation?
At the juncture of the jugular and subclavian veins
What is Lipemia? When does it occur?
Lipid in the blood.
W/in an hour after eating a fatty meal
What is the half-life of chilomicrons?
Less than 60 minutes, so plasma usually becomes clear within a few hours
What is the fate of chilomicrons?
Removed from blood as they pass thru the capillaries of adipose tissue and the liver
What enzyme does adipose tissue and the liver contain large quantities of?
Lipoprotein lipase
Where is lipoprotein lipase especially active?
In the capillary enthothelium
What does lipoproteinn lipase do?
Hydrolyzes the TGs of chylomicrons into FAs and glycerol, which diffuse into adipocytes (storage) & hepatocytes (re-packaged into lipoproteins and exported to blood)
Can tissues use the contents of chylomicrons?
Yes, sir!
What are the five general types of lipoproteins?
Chylomicrons VLDL IDL LDL HDL
Where are chylomicrons synthesized?
By the enterocytes of the small intestine.
What lipoproteins does the liver synthesize?
VLDL, IDL, LDL and HDL
What do VLDLs contain?
High TGs, moderate cholesterol and phospholipids
What do IDLs contain?
Moderate TGs, cholesterol and phospholipids
What do LDLs contain?
Low TGs, high cholesterol and phospholipids
What do HDLs contain?
Lows TGs, cholesterol and phospholipids
What are the only two lipoproteins routinely monitored clinically to screen for atherosclerosis, MI and stroke risk, and heart disease?
LDL-C and HDL-C
What are the most effective drugs currently in use for treating elevated LDL-C?
Statins (Lipitor, Crestor, Lescol, Mevacor, etc)
What are the adverse effects of statins?
Myopathy
What is Myalgia? Myositis? Rhabdomyolysis?
Myalgia is muscle pain/weakness w/o inreased creatine kinase VS Myositis also includes elevated CK.
Rhabdomyolysis has very high CK (>10 times the upper normal limit), increased serum creatinine, often with dark urine and myoglobinuria
What does dark urine and myoglubinuria indicate?
Muscle damage
T/F all statins have been associated with myopathy?
T
How many pts out of 10 report having muscle complaints?
1 in 10
What are risk factors for myopathy?
Being elderly, small size, high statin dose, liver or renal disease, diabetes, uncontrolled hypothyroidism, and interacting medications
What was the first lipid lowering agent?
Niacin (Vit B3)
What are the three basic preparations of niacin?
Immediate release, sustained release, and extended release
What is no-flush niacin? Does it work?
Inositol hexaniacinate/niacinamide. No, it is worthless
What is the mechanism of action of Niacin?
Reduces production of VLDL, which leads to a secondary reduction of LDL
What is the most potent agent for raising HDL?
Niacin
Is intolerance to Niacin common?
Yes, only 50-60% of pts may be able to take full doses
What are the adverse effects of Niacin? How can this be mitigated?
Flushing. Take ASA or NSAIDs 30-45 minutes prior to each niacin dose (blunts this prostaglandin-mediated effect)
Why are Bile Acid binding resins taken?
Some take when statins do not lower the LDLs enough
What do Bile Acid binding resins do?
Bind bile acids in your gut
What happens if you bind bile acids with resins?
Can’t emulsify fats, means you can’t digest/absorb fat as well
Do resins affect HDL or TGs?
No, not much. Will lower LDLs
What happens if you don’t breakdown/absorb fat?
It stays in your gut and becomes part of the stool
What are the consequences of fat remaining in stool?
Constipation
What can relieve constipation and bloating?
Increased dietary fiber or fiber supplement (Metamucil)
What are the drug interactions of bile binding resins?
Interfere with: Fat soluble vitamins. Folate Thiazides Tetracyclines Warfarin Propanolol Penicillin
What is one way of avoiding some of the drug-drug interactions of resins?
Take resins a few hours AFTER taking the affected medications
All H2O absorption in the small intestine is what type?
Passive and secondary to solute movement
What stimulates water absorption in the small intestine?
Solutes such as Na+, glucose, amino acids
How is most K+ absorbed?
Passively when luminal [K+] rises b/c of absorption of water (solvent drag)
Where does calcium absorption occur? What is it primarily regulated by?
In the Duodenum and jejunum.
Regulated by Vitamin D3
What does vitamin D do?
Stimulates synthesis of Ca++binding proteins called calbindins in enterocytes
How are fat soluble vitamins (ADEK) absorbed in the small intestine?
Similar to fat
How are more water-soluble vitamins absorbed in the small intestine?
By simple diffusion
What water soluble vitamin requires intrinsic factor?
B12
What cells absorb IF-B12 complexes across the brush border?
Ileal cells
What does atrophy of gastric mucosa result in?
Deficiency of IF and acid secretion that causes VitB12 deficiency
Where do peristaltic contractions occur?
Esophagus, stomach, and small intestine
How long does it take chyme to move across the entire Small Intestine via peristalsis?
3-5 hours
What is segmentation?
A series of contractile and relaxation periods that mechanically digests food
What is peristalsis and segmentation controlled by?
Autonomic nervous system - SNS generally inhibit, while paraSNS generally excite muscular activity
