Function Of The Kidneys

Function of the kidneys

Ultrafiltration • Blood enters the renal capsule through the afferent arteriole • Divides into a network of capillaries (glomerulus) • Leaves the renal capsule through the efferent arteriole

• Blood enters glomerulus under high pressure – Afferent arteriole is wider than efferent arteriole causing a build up of hydrostatic pressure

• Pressure forces water and dissolved blood components into the cavity of the renal capsule – Up to a relative molecular mass of 70 000 – filtrate

Structure

Pathway of filtrate • Capillary walls are made up of endothelial cells with pores between them. • Through the basement membrane • Through podocytes – Make up inner layer of renal capsule – Cells lifted off the surface membrane on little feet

Adaptations • Endothelial cell pores- do not restrict passage – Filtrate does not have to go through them

• Basement membrane allows only the passage of smaller molecules • Pressure build up due to narrowing of efferent arteriol

Resistance to filtration • • • •

Capillary endothelium Basement membrane Epithelial cells of renal capsule Intracapsular pressure- the hydrostatic pressure of the fluid in the renal capsule • Low water potential of blood in the glomerulus

Hydrostatic pressure of blood is great – Overcomes the resistant – Referred to as effective filtration pressue