This fluid occupies the intracellular space and forms the connecting link in the transport of nutrition, gases and the metabolic end products between blood capillaries, tissue cells and the lymph. It constitutes the internal environment of the body, which surrounds tissue cells. It is obvious that anything that increases the capillary permeability will increase the amount of tissue fluid formed.
Regarding blood pressure and osmotic pressure, it is known that at the arterial end of capillaries, the average blood pressure is about 32 mm of Hg and at the venous end, 10 mm of Hg. The colloidal osmotic pressure at both ends is same 25 mm of Hg on the average. At the arterial end, the net filtration pressure which is the difference between the two is 7 mm of Hg towards the tissue interstitial fluid. At the venous end due to fall in blood or hydrostatic pressure, the filtration pressure is 15 mm of Hg to the opposite side, i.
The amount of tissue fluid formed from the tissue cells depends upon the degree of metabolic activity of the cells. Tissue cells produce water as an end product of metabolism. This metabolic water is added to the already existing tissue fluid. More the degree of activity more will be the metabolic water formed and consequently the amount of tissue fluid will increase. It is very difficult to obtain a pure sample of tissue fluid; hence, its exact composition is not known.
It is believed that its composition is same as that of lymph, excepting that its protein content is negligible; and as such, its colloidal osmotic pressure is very low. The composition and volume of tissue fluid is regulated by constant interchange with blood and lymph. It has been mentioned above that filtration of tissue fluid takes place at the arterial end of the capillaries.
At the venous end of the capillary the blood pressure is very low—about 10 mm of Hg and the colloidal osmotic pressure is much higher. These two factors help in drawing away just as much fluid comes out from the arterial side.
As we know that water content of tissue fluid is derived from two sources—blood and tissue cells. The amount of water that goes out of blood is drawn in again at the venous side of the capillaries. But vascular capillaries cannot draw away the amount of metabolic water formed by the tissue cells.
It is for the drainage of this excess water that the lymphatic system has developed. Thus it will be seen that blood and lymph remain as if on two sides of tissue fluid and try to keep it constant in volume and composition by continuous interchange. Specific gravity of the tissue fluid is about 1. It may contain a few erythrocytes.
But regarding the white cells, the tissue fluid contains a good number of lymphocytes and a small number of granulocytes. Blood proteins and nutrient contents of it are very low. It does not contain platelets and may also clot, but with a very slow process. It contains higher concentration of waste products but glucose, salt and water contents are more or less same as those are present in blood.
It constitutes the internal medium in which the tissue cells are bathed. The cells draw in oxygen and nutrition from the tissue fluid and excrete their metabolites into it. Hence, tissue fluid may be regarded as the medium which supplies all the immediate requirements of the cell.
It acts as a great reservoir of water, salts, nutrition, etc. This function is very important. Under any condition, in which the blood volume is increased or diminished, physical forces are set up by which the blood volume is kept constant with the help of the tissue reserve.
For example in haemorrhage, the capillary pressure becomes very low and goes below the colloidal osmotic pressure in the capillary which remains same.
Due to this higher O. P in the capillaries, water is drawn in from the tissue spaces, so that blood volume is restored. When water is drawn away from blood, such as due to diuresis, excessive sweating or diarrhoea, blood volume and blood pressure will be lowered, but the plasma proteins will be more concentrated.
This will increase the colloidal O. This increased osmotic pressure of plasma and reduced blood pressure will increase the rate of absorption from the tissue fluid, and thus blood volume will be kept constant. On the other hand, when blood volume increases, as for instance, by intravenous injection of large quantities of isotonic saline, fluid will pass out into the tissue spaces due to two causes:.
Increased volume of blood will raise the blood pressure and cause more filtration. Both these factors will cause more fluid to run out into the tissue spaces, until blood volume comes back to the original level.
Swelling or oedema observed sometimes in different parts of the body is due to the aggregation of the tissue fluid. Increase in the capillary pressure which might be due to changes in posture in lower extremities it is due to continued standing , obstruction to veins or rise in the venous pressure as observed in the cardiac failure. Blockage of lymphatic nodes or vessels, as a result of inflammation of the node or blockages by very small worms like that of Filaria.
Screening Tests. Diagnosis and Staging. Questions to Ask about Your Diagnosis. Types of Cancer Treatment. Side Effects of Cancer Treatment.
Clinical Trials Information. A to Z List of Cancer Drugs. Questions to Ask about Your Treatment. Feelings and Cancer. Adjusting to Cancer. Day-to-Day Life. Support for Caregivers. Questions to Ask About Cancer. Choices for Care. Talking about Your Advanced Cancer. Planning for Advanced Cancer. Advanced Cancer and Caregivers. Questions to Ask about Advanced Cancer.
Managing Cancer Care. Finding Health Care Services. Advance Directives. Using Trusted Resources. Coronavirus Information for Patients. Clinical Trials during Coronavirus. Adolescents and Young Adults with Cancer.
Emotional Support for Young People with Cancer. Cancers by Body Location. Late Effects of Childhood Cancer Treatment. Pediatric Supportive Care. Rare Cancers of Childhood Treatment. Childhood Cancer Genomics. Study Findings. Metastatic Cancer Research.
Intramural Research. Extramural Research. Cancer Research Workforce. Partners in Cancer Research. What Are Cancer Research Studies. Research Studies. Get Involved.
Cancer Biology Research. Cancer Genomics Research. Research on Causes of Cancer. Cancer Prevention Research. Cancer Treatment Research. Cancer Health Disparities. Childhood Cancers Research. Global Cancer Research. Cancer Research Infrastructure. Clinical Trials.
Frederick National Laboratory for Cancer Research. Bioinformatics, Big Data, and Cancer. Annual Report to the Nation. Research Advances by Cancer Type. Stories of Discovery. Milestones in Cancer Research and Discovery. Biomedical Citizen Science. Director's Message. Budget Proposal.
Stories of Cancer Research. Driving Discovery. Highlighted Scientific Opportunities. Research Grants. Research Funding Opportunities.
0コメント