State the functions of tissue fluid and describe the formation of tissue fluid in a capillary network

Sourav PanOctober 29, 2024

Answered

Functions of Tissue Fluid

Tissue fluid, also known as interstitial fluid, is the fluid that surrounds the cells in tissues and plays several important roles:

1. Nutrient Supply: Tissue fluid provides a medium through which nutrients (like glucose, amino acids, and electrolytes) can diffuse from the capillaries to the cells, supporting cellular metabolism.
2. Waste Removal: It facilitates the removal of metabolic waste products (such as carbon dioxide and urea) from the cells to the capillaries, where they can be transported to excretory organs.
3. Transport Medium: Tissue fluid acts as a transport medium for hormones, enzymes, and other signaling molecules, allowing for communication between cells.
4. Hydration: It helps maintain cell turgor and hydration, ensuring cells remain functional and healthy.
5. Immune Function: Tissue fluid contains white blood cells and antibodies, contributing to the body’s immune response by allowing immune cells to reach infected or damaged tissues.

Formation of Tissue Fluid in a Capillary Network

The formation of tissue fluid occurs primarily in capillary networks and involves several key processes:

1. Blood Filtration:
   • As blood flows through the capillaries, the hydrostatic pressure (the pressure exerted by the fluid) is higher inside the capillary than in the surrounding tissue fluid.
   • This pressure forces some of the plasma (the liquid component of blood) out of the capillaries and into the surrounding tissues, creating tissue fluid.
2. Capillary Permeability:
   • Capillaries have thin walls (one endothelial cell thick), which allow small molecules, ions, and water to pass through easily.
   • The permeability of the capillary walls determines the volume and composition of tissue fluid.
3. Osmotic Pressure:
   • Along with hydrostatic pressure, osmotic pressure plays a role in tissue fluid formation. The proteins (primarily albumin) in the blood plasma exert osmotic pressure, drawing water back into the capillaries from the tissue fluid.
   • This osmotic pressure balances the hydrostatic pressure, preventing excessive loss of fluid from the capillaries.
4. Balance Between Pressures:
   • The net movement of fluid across the capillary walls is determined by the balance between hydrostatic pressure (which promotes filtration) and osmotic pressure (which promotes reabsorption).
   • In general, fluid tends to leave the capillaries at the arterial end (due to higher hydrostatic pressure) and is reabsorbed at the venous end (where osmotic pressure predominates).
5. Formation of Lymph:
   • Excess tissue fluid that does not return to the capillaries enters the lymphatic system, where it is called lymph. This fluid is eventually returned to the bloodstream, helping maintain fluid balance in the body.