Describe how the ultrastructure of the glomerulus and Bowman’s capsule facilitate ultrafiltration.

The filtration barrier between blood and filtrate comprises of 3 main structures: fenestrated endothelium of the arteriole, glomerular basement membrane and specialised cells called podocytes with slit diaphragms encapsulating the blood vessel. The barrier prevents passage of cells and big molecules such as proteins. The filtrate contains water, electrolytes and sometimes glucose that is later reabsorbed in the nephron.Moreover, ultrafilration occurs thanks to high hydrostatic pressure that pushes the blood against the barrier. What facilitates the formation of the high pressure is the fact that the afferent (entering) arteriole is wider than the efferent (leaving) arteriole, hence it is easier for the blood to enter the glomerulus than leave it.