Tissue fluid and its formation

• Tissue fluid is a yellowish liquid made from blood plasma, bathing all tissues and acts as a transport medium between the blood and cells
• Tissue fluid supplies water, amino acids, fatty acids, salts and carbohydrates to tissues and receives carbon dioxide and other waste products from respiring tissues
• Plasma proteins are too large to leave and remain in the capillaries which greatly reduce water potential
• Substances like water, oxygen, glucose pass through the capillary wall at the arteriole end due to hydrostatic pressure being higher than the water potential gradient
• At the venule end, water is returned to the capillaries due to the higher hydrostatic pressure outside the capillary, and the water potential gradient
• Remaining tissue fluid (water and lipids) enters the lymph vessels
• As the capillaries are narrower than the arterioles, pressure builds up which forces water out of the blood plasma - hydrostatic pressure