Differences blood, tissue fluid and lymph
- hormones, plasma proteins, erthrocytes, leucocytes, platelets, glucose, lipoproteins (fatty material), oxygen, carbon dioxide, amino acids, no fats
- Tissue fluid
- some hormones, some phagocytic WBCs, less 02 and nutrients, more CO2, proteins secreted by cells, less amino acids
- lymphocytes (made in lymph nodes [swellings found in intervals accross lymphatic sys] engulf and digest pathogens, part of immune sys), less o2 and nutrients, more C02, more fatty materials (absorbed from lacteals in intestines), less glucose, less amino acids
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Formation of tissue fluid and lymph
- At the arterial end of the capillary, the blood is at higher pressure due to the contraction of the heart, this is known as hyrdostatic pressure. It pushes fluid out of the capillary through tiny gaps in the capillary wall (tissue fluid)
- Plasma proteins, erythrocytes... too big to be pushed out of gap
- Tissue fluid surrounds body cells to allow diffusion/faciliated diffusion to occur across their cell surface membranes.
- Tissue fluid also contains some hydrostaic pressure, pushing it back into the capillary wall
- Both tissue and blood fluid have a negative water potential as they contain solutes. However, tissue fluid has a less negative water potential causing water to move back into the blood by osmosis.
- The combined effect of the hydrostatic pressure from the tissue fluid and the osmotitc force of the plasma proteins is sufficient to move tissue fluid back into the capillary
- Not all tissue fluid is pushed back in the capillary, excess is drained away by the lympatic system which eventually rejoins the blood in the chest cavity.
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