Can capillaries secrete some substances?

Question

our vessel---capillaries can keep pH at a wonderful level by secreting what substance???

Answer 1

Lymph originates as blood plasma that leaks from the capillaries of the circulatory system, becoming interstitial fluid, and filling the space between individual cells of tissue. Plasma is forced out of the capillaries (called filtration) and forced back in (called absorption) due to interactions of hydrostatic pressure (favoring movement out of the capillaries) and oncotic pressure (favoring movement into the capillaries). While out of the capillaries, the fluid mixes with the interstitial fluid, causing a gradual increase in the volume of fluid. Most of the fluid is returned to the capillaries. The proportion of interstitial fluid that is returned to the circulatory system by osmosis is about 90% of the former plasma, with about 10% accumulating as overfill. The excess interstitial fluid is collected by the lymphatic system by diffusion into lymph capillaries, and is processed by lymph nodes prior to being returned to the circulatory system. Once within the lymphatic system the fluid is called lymph, and has almost the same composition as the original interstitial fluid.

Answer 2

pH is a measurement of the acidity of a solution, and is determined by the concentration of hydrogen ions (H+) in solution.

The pH of the body fluids is regulated by several systems: chemical buffering systems; the respiratory system; and the kidneys.

Chemical:
There are three major chemical buffering systems in our body which function to regulate pH:
1) Bicarbonate buffers
2) Phosphate buffers
3) Protein buffers

Of which, the bicarbonate buffering system is especially important. CO2 + H2O <-----> H2CO3 <-----> H+ + HCO3-
In the tissues CO2 is produced by the cells, enters the red blood cell in the plasma where it combines with water to form carbonic acid which then dissociates to the bicarbonate ion and the hydrogen ion. The bicarbonate ion leaves the red blood cell and enter the plasma where it is transported to the lungs. The hydrogen ion is buffered by the hemoglobin in the red blood cell.


Respiratory:
In the lungs the carbon dioxide level is low, it is being expired from the body, and the reaction reverses itself with the hydrogen combining with bicarbonate ion to form carbonic acid which then dissociates to water and carbon dioxide. The carbon dioxide is then exhaled from the lungs.

Kidneys:
The kidney can neutralize more acid or base than either the chemical buffering systems or the respiratory system.

Renal tubules in the kidneys secrete H+ into the tubular fluid where it can pass out in the urine, so your the kidneys have the ability to directly remove hydrogen ions from the blood rather than simply buffer them.

In the end...
In all three methods of pH regulation methods, the control of pH involves the bicarbonate buffer. The two major factors in this relationship are the bicarbonate ion concentration and the carbon dioxide concentration, expressed as
pH =pKa + log [ HCO3-] / [CO2]

[ ] brackets signify concentration

Answer 3

potassium