The urinary tubule is the functional unit of the kidney. Each urinary tubule begins in the cortex as a cup like structure called the Bowman's capsule. The capsule opens into a short coiled tube, the proximal convoluted tubule. Then it straightens out as it passes into the medulla, where it makes a U-shaped loop, the Henle loop, before reentering the cortex. In the cortex. The tubule becomes coiled again to form the distal convoluted tubule. The tubule bends once more and completes its course in the medulla.
The tubule widens as it approaches the pelvis. Together with many other tubules, it pours its contents into wider main collecting ducts which eventually join up and open into the pelvis st the apices of pyramids.
All along its course, the tubule is closely associated with several networks of blood capillaries. The renal artery branches in the kidney. Each branch breaks into a made of blood capillaries in the Bowman's capsule. This knot of capillaries is called the glomerulus. The capsule and glomerulus form the malpighian capsule. The capillaries in the glomerulus rejoin to form a blood vessel leading out of the capsule. This vessel then branches into a capillary network around the urinary tubule before rejoining to form a branch of the renal vein.
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