Question

1. Explain the significance of pressures involved in filtration and reabsorption processes. Briefly present the factors causing cardio-renal syndromes.

2. List the most important mechanisms involved in acid-base balance regulation. Are there any hormones involved in this process?

3. What effect would furosemide, an inhibitor of Na+ reabsorption by the thick ascending limb of Loop of Henle, have on urinary Na+, K+ and Ca++ excretion?

4. Why there is no universal donor anymore? What type of blood you can transfuse if patient has type A- blood?

Answer 1

Cardiovascular system circulate gases, nutrients, wastes, and other substances to and from the cells of the body. This can be done by diffusion but the mass movement of fluids into and out of capillary beds requires a transport mechanism referred to as bulk flow, which involves two pressure-driven mechanisms:

Filtration

Volumes of fluid move from an area of higher pressure in a capillary bed to an area of lower pressure in the tissues via filtration.

Reabsorption

Movement of fluid from an area of higher pressure in the tissues into an area of lower pressure in the capillaries.
Filtration and reabsorption is carried out by interaction of two different pressure: hydrostatic pressure and osmotic pressure.

Hydrostatic pressure

Transport fluid between the capillaries and tissue.

Osmotic Pressure

The net pressure that drives reabsorption—the movement of fluid from the interstitial fluid back into the capillaries.

Hydrostatic pressure forces fluid out of the capillary, osmotic pressure draws fluid back in.

The net filtration pressure represents the interaction of the hydrostatic and osmotic pressures, driving fluid out of the capillary. It is equal to the difference between the CHP (capillary hydrostatic pressure) and the BCOP (blood colloidal osmotic pressure).

CHP
Pressure exerted by blood against the wall of a capillary is called capillary hydrostatic pressure (CHP)

BCOP
Pressure created by the concentration of colloidal proteins in the blood is called the blood colloidal osmotic pressure (BCOP)

Mass flow of fluid through net filtration pressure (NFP)

Net filtration at capillary end
Fluid exit capillary when capillary hydrostatic pressure (CHP) is greater than blood colloidal osmotic pressure (BCOP).

Mid point
There is no net movement of fluid near the midpoint because the pressure is equal between CHP and BCOP.

Net reabsorption at venous end
Fluid reenters capillary when the BCOP is greater than CHP.

Cause of cardio-renal syndrome
The general cause of cardio-renal syndrome is hemodynamic factors, such as intrarenal hemodynamics, transrenal perfusion pressure and systemic neurohormonal factors.