Capillary Exchange & Lymphatic System PDF

Capillary exchange: Capillary exchange is the movement of substances into and out of capillaries. The cells are bathed in interstitial fluid (extracellular fluid) Transport (diffusion) in and out of cells requires a pressure gradient (going from high to low) Interstitial fluid needs constant turnove...

Capillary exchange: Capillary exchange is the movement of substances into and out of capillaries. The cells are bathed in interstitial fluid (extracellular fluid) Transport (diffusion) in and out of cells requires a pressure gradient (going from high to low) Interstitial fluid needs constant turnover Diffusion: Oxygen, hormones, and nutrients diffuse from a high concentration in the capillary to a low concentration in the interstitial fluid. Lipid soluble substances (O2, CO2, steroid hormones, fatty acids) diffuse through the plasma membrane of endothelial cells. Water soluble (glucose, amino acids) diffuse through intercellular spaces or the fenestrations of capillaries. The spaces between cells are very small and very few molecules can pass e.g. blood-brain barrier (protects the brain from toxins). In large spaces between endothelial cells, proteins and whole cells can pass, for example in the liver or spleen. The Lymphatic System consists of: The lymphatic system is made up of lymphoid organs such as the spleen, thymus, and tonsils, lymphoid tissues and cells such as the lymphocytes B and T cells, Lymph, Lymphatic ducts, trunks, vessels, capillaries and Lymph nodes. Cardiovascular-Lymphatic link: Capillary permeability, blood pressure, and osmotic pressure affect the movement of fluid from capillaries. Fluid moves out of capillaries into interstitial (intercellular) space and most returns to capillaries. The fluid that remains in tissues is picked up by the lymphatic capillaries and then eventually returned to venous circulation. The cardiovascular-lymphatic link maintains blood volume, pressure, and fluid balance Edema: Edema (oedema) is swelling caused by excess fluid accumulation in body tissues (interstitial space). Edema is caused by problems with capillaries, heart failure, kidney disease, liver problems, pregnancy, problems with lymphatic system, standing or walking a lot in hot weather, and eating too much salt. If capillaries become ‘leaky’, proteins can leak into the interstitial fluid. This increases the osmotic pressure (osmolarity) outside the capillary and draws more fluid from the capillaries into the interstitial fluid.