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Anatomy and Physiology 2

Rock Levinson, PhD

Q: How effective is dialysis relative to normal kidney function and why is it so much less effective?
A: Dialysis was developed in the last 50 years. The kidney has been under development for millions of years; it is clearly a superior product. Dialysis uses only one kind of membrane, so for some substances it is not optimal. The kidney uses many different molecular pumps and specialized cells to do its job. One day we will surely have true “artificial kidneys”.

Q: What was the root cause of your blocked arteries?
A: Genetics, mostly. Early heart disease runs in the family.

Q: Why, in boxing/fighting matches, are kidney punches so frowned upon? Are the kidneys overly susceptible to trauma injury?
A: Yes they are, as they are suspended in a fairly moveable tissue (“fascia”) up against the back, and can be rattled around by a blow. It’s been said that all professional football players have hematuria (blood in the urine) after a game.

Q: How does a pacemaker work? Does it shock the heart through cell-contacts?
A: Yes, it has a battery-driven computer that feeds electricity to a pair of electrodes that are inserted in the heart muscle near the heart’s natural pacemaker. Some pacemakers can alter the heart rate to meet demand for more blood, as in exercise.

Q: How does dialysis work?
A: It depends on a semi-permeable membrane, which salts and other small molecules can pass through. Blood is pumped through the machine and the dialysis fluid, on the other side of the membrane from the blood, takes away the excess unneeded salts and metabolites while maintaining the concentration of molecules that are essential. In peritoneal dialysis, the dialysis fluid is inserted into the peritoneum, the abdominal cavity that contains the intestines; its own lining serves as the dialysis membrane.

Q: How does osmolarity relate to when your hands get “pruny” after swimming?
A: If you swam is an isotonic solution (same osmolarity as your plasma or tissue fluid) there would be no exchange of water between skin and pool, and you wouldn’t prune out. I think.

Q: What happens in the heart during a premature ventricular contraction?
A: A little irritable area in the AV node (the area between the atrium and the ventricle) contracts without listening to the normal flow of electricity, making the ventricle contract suddenly. As it is relaxing and repolarizing, it misses the normal signal, so it waits for the next one. But that time it’s very full of blood, and you get the whopper of a contraction (a palpitation), which can make you jump and makes some people cough, your heart hits your diaphragm so hard! Then things usually are normal for a while. PVCs are not necessarily the sign that something is wrong with the heart; stress can trigger them.

Q: How can lung damage be reversed as a result of smoking cessation? To what extent can the alveoli repopulate, and how long does it take?
A: In some people it can go back to nearly normal, in others not. Duration of smoking is important; the rest is not very predictable. We have cells that can heal damage, but if scar formation has happened that can’t be reversed.