Urinary System Facts

Typically, every human has two kidneys. The kidneys are bean-shaped organs about the size of a bar of soap. The kidneys lie in the abdomen, posterior or retroperitoneal to the organs of digestion, around or just below the ribcage and close to the lumbar spine. The kidneys are surrounded by what is called peri-nephric fat, and situated on the superior pole of each kidney is an adrenal gland. The kidneys receive their blood supply of 1.25 L/min (25% of the cardiac output) from the renal arteries which are fed by the Abdominal aorta. This is important because the kidneys' main role is to filter water soluble waste products from the blood. The other attachment of the kidneys are at their functional endpoints the ureters, which lies more medial and runs down to the trigone of the bladder. Functionally the kidney performs a number of tasks. In its role in the urinary system it concentrates urine, plays a crucial role in regulating electrolytes, and maintains acid-base homeostasis. The kidney excretes and re-absorbs electrolytes (e.g. sodium, potassium and calcium) under the influence of local and systemic hormones. pH balance is regulated by the excretion of bound acids and ammonium ions. In addition, they remove urea, a nitrogenous waste product from the metabolism of proteins from amino acids. The end point is a hyperosmolar solution carrying waste for storage in the bladder prior to urination. Humans produce about 1.5 liters of urine over 24 hours, although this amount may vary according to circumstances. Because the rate of filtration at the kidney is proportional to the glomerular filtration rate, which is in turn related to the blood flow through the kidney, changes in body fluid status can affect kidney function. Hormones exogenous and endogenous to the kidney alter the amount of blood flowing through the glomerulus. Some medications interfere directly or indirectly with urine production. Diuretics achieve this by altering the amount of absorbed or excreted...