The kidney's structure, functions, and what controls these functions.

The kidney is made up of nephrons, which are a kidney's functional units. These nephrons collect fluid filtered from the blood. The kidney connects to the renal artery, renal, vein, and ureter. Purified blood leaves the kidney using the renal vein, urine leaves using a ureter and the renal artery carries blood from the aorta to the kidney. The nephron has a cup-shaped nephric capsule that surrounds a cluster of capillaries called the glomerulus. A …

…salt content. Since less salt is resorbed by the kidney the urines salt content increases therefore increasing urinary volume. When the sodium levels in the blood decrease the kidneys secrete and enzyme called renin. Renin converts the plasma protein angiotensinogen into the hormone angiotensin. Angiotensin causes the constriction of blood vessels to increase the aldosterone secretion. Then the aldosterone promotes the resorption of sodium by the kidney and the urine's salt content decreasing urinary volume.