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Fluid Balance - Coggle Diagram
Fluid Balance
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Distribution of ECF
- bulk flow - movement of large amounts of fluid and dissolved substances together in response to pressure gradients/differences across the capillary wall, via the processes of filtration and reabsorption
- filtration - pressure inside capillaries pushes fluid outward into interstitial fluid/tissues
- reabsorption - pressure outside capillaries pushing fluid into blood from interstitial fluid/tissues
- capillary hydrostatic pressure - pressure exerted by blood on capillary walls
- interstitial fluid oncotic osmotic pressure - pressure exerted by proteins in interstitial fluid
- interstitial fluid hydrostatic pressure - pressure exerted by interstitial fluid
plasma oncotic osmotic pressure - osmotic pressure exerted by large proteins in plasma
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Blood Osmolarity
- Hypothalamic osmoreceptors detect an increase in blood osmolarity
- hypothalamus stimulates ADH release from the anterior pituitary gland
- ADH acts on nephrons to reabsorb more water into the blood
- urine concentration increases and blood concentration decreases
- gases, nutrients and waste can only diffuse in one direction, restricting ion fluctuation between ICF and ECF
Oedema
- abnormal/excess accumulation of fluid in interstitial tissues
Main Causes
- Increased hydrostatic pressure - caused by kidney failure, heart failure or vessel obstruction, as the heart is pumping against a greater resistance (hypertension) inducing heart failure and decreased venous return
- Decreased Oncotic Pressure - caused by a decrease in plasma proteins from liver failure, malnutrition or nephrotic syndrome, as reabsorption is inhibited and blood volume is decreased, stimulating renin, and RAAS to increase blood volume and pressure
- Lymphatic Obstruction
- Increased Vascular Permeability - caused by inflammatory response as histamine is released and endothelial cells allow proteins and more fluid to enter interstitial fluid, increasing interstitial oncotic pressure and decreasing plasma oncotic pressure
Extracellular Fluid
- 1/3 of the body's water content
- composed of blood plasma and interstitial fluid
Intracellular Fluid
- 2/3 of the body's water content
- composed of water and dissolved solutes
Interstitial Fluid
- fluid surrounding cells
- facilitates exchange of gases, nutrients and waste between cells and blood vessels