Urinary System Health Article

Definition

The urinary system consists of organs, muscles, tubes, and nerves that are responsible for producing, transporting, and storing urine. The major structures of the urinary system include the kidneys, the ureters, the bladder, and the urethra.

The kidneys

The two kidneys are located lateral (to each side) to the spinal column, along the posterior (back) wall of the abdominal cavity. Each kidney is bean-shaped and approximately the size of one's fist (4 to 5 in, or 10 to 13 cm in length). The hilus is the indentation found along the medial side (the side closest to the midline of the body) of the kidney and is the point at which blood vessels (the renal artery and renal vein), nerves, and the ureter enter and exit the organ. The outer layer of the kidney is called the renal cortex, and the inner region of the organ is called the renal medulla.

The individual filtering unit of the kidney is called a nephron, of which there are approximately one million in each kidney. Each nephron extends from the renal cortex into the renal medulla and empties into the funnel-like reservoir of the kidney called the renal pelvis. There are three major components of the nephron: Bowman's capsule, the glomerulus (plural, glomeruli), and the renal tubule. Bowman's capsule is a structure that contains the glomerulus, a cluster of capillaries that is the main filtering device of the nephron. The afferent arteriole brings blood from the branches of the renal artery into Bowman's capsule, where fluid is filtered through the glomerulus. Blood exits the glomerulus by way of the efferent arteriole, passing through the persitubular capillaries and eventually entering the renal vein. The renal tubule has four main sections: the proximal tubule, the loop of Henle, the distal tubule, and the collection tubule. The end closest to Bowman's capsule is called the proximal tubule. The loop of Henle extends from the proximal tubule in the renal cortex to the medulla and back to the cortex, into the distal tubule. The distal tubule empties

into a collecting duct which in turn empties into the renal pelvis.