Each nephron consists of a single long tubule as well as a ball of capillaries called the glomerulus. The blind end of the tubule forms a cup-shaped swelling, called Bowman’s capsule, which surrounds the glomerulus. Filtrate is formed when blood pressure forces fluid from the blood in the glomerulus into the lumen of Bowman’s capsule. Processing occurs as the filtrate passes through three major regions of the nephron: the proximal tubule, the loop of Henle (a hairpin turn with a descending limb and an ascending limb), and the distal tubule. A collecting duct receives processed filtrate from many nephrons and transports it to the renal pelvis.
Each nephron is supplied with blood by an afferent arteriole, an offshoot of the renal artery that branches and forms the capillaries of the glomerulus. The capillaries converge as they leave the glomerulus, forming an efferent arteriole. Branches of this vessel form the peritubular capillaries, which surround the proximal and distal tubules. Other branches extend downward and form the vasa recta, hairpin-shaped capillaries that serve the renal medulla, including the long loop of Henle of juxtamedullary nephrons.

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