fluidinterstitial

Fluidinterstitial refers to the interstitial fluid, the extracellular fluid that bathes the body's cells in the spaces between tissues. It is a major component of the extracellular fluid, distinct from plasma in blood vessels and from transcellular fluids such as cerebrospinal or synovial fluids. The interstitial compartment forms the immediate extracellular environment for most cells and serves as the primary medium for exchange of nutrients, gases, and wastes between blood and cells.

Composition and function: Interstitial fluid is largely water with dissolved ions such as sodium, chloride, and bicarbonate, as well as small nutrients, signaling molecules, and waste products. Protein concentration in interstitial fluid is lower than in plasma. Its functions include delivering nutrients and oxygen to cells, removing metabolic wastes, facilitating immune surveillance, and contributing to tissue hydration and mechanical cushioning.

Formation, exchange, and homeostasis: Interstitial fluid is continually formed by filtration of plasma across capillary walls. Its movement into tissues is governed by Starling forces, including capillary hydrostatic and oncotic pressures. Fluid is reabsorbed back into capillaries or drained via the lymphatic system, which helps maintain fluid balance and immune function. Disruptions in this balance can alter interstitial volume and composition.

Clinical relevance: Abnormal accumulation of interstitial fluid leads to edema, which may result from increased capillary filtration, decreased oncotic pressure, impaired lymphatic drainage, or sodium and water retention. Measurement and study of interstitial fluid, including lymphatic function and interstitial pressure, support understanding of tissue edema and related conditions.