N30.0 Acute cystitis

Excludes1 irradiation cystitis (N30.4-)

trigonitis (N30.3-)

Pyeloileostomy, urinary diversion

Pyeloplasty

Pyelorrhaphy

Pyeloscopy

Pyelostomy

Pyelotomy

Functions of the Urinary System

The major function of the urinary system is to continually maintain a healthy balance of the amount and content of extracellular fluids within the body. Biologists use the term homeostasis to describe this important process. The process of metabolism changes food and liquid (with its requisite fats, carbohydrates, and proteins) into building blocks, energy sources, and waste products. To operate efficiently, the body needs to constantly monitor and rebalance the amounts of these substances in the bloodstream. The breakdown of proteins and amino acids in the liver leaves chemical wastes, such as urea, creatinine, and uric acid, in the bloodstream. These wastes are toxic, nitrogenous substances that must be excreted in the urine. The act of releasing urine is called urination, voiding, or micturition.

Anatomy and Physiology

The urinary system is composed of two kidneys, two ureters, a urinary bladder, and a urethra (Figs. 6-1 and 6-2). The work of the urinary system is done by a specialized tissue in the kidneys called parenchymal tissue. The kidneys function to filter the blood and eliminate waste through the passage of urine. The ureters are thin, muscular tubes that move urine in peristaltic waves from the kidneys to the bladder. The urinary bladder is the sac that stores the urine until it is excreted. The bladder is lined with an epithelial mucous membrane of transitional cells. Underneath, a layer termed the lamina propria is composed of connective tissue that holds the blood vessels and nerves. The detrusor muscle is the final coat; it normally contracts to expel urine. The urethra is the tube that conducts the urine out of the bladder. The opening of the urethra is called the urinary meatus. The triangular area in the bladder between the ureters’ entrance and the urethral outlet is called the trigone. The ureters, bladder, and urethra are all stromal tissue, which is a supportive tissue.

The Kidney

Because the kidneys are primarily responsible for the functioning of the urinary system, it is helpful to look at them in greater detail. Each of the two kidneys is located high in the abdominal cavity, tucked under the ribs in the back and behind the lining of the abdominal cavity (retroperitoneal). The normal human kidney is about the size of a fist. The tough outer covering of the kidney is the renal capsule. If a kidney were sliced open, the outer portion, the cortex (pl. cortices), and the inner portion, called the medulla (pl. medullae), would be visible (Fig. 6-3). The renal pelvis and calyces (sing. calyx) are an extension of the ureter inside the kidney. The renal pyramids are triangular sections that extend from the renal medulla toward the renal pelvis. The downward point of the pyramid is referred to as the papilla. The term renal means “pertaining to the kidneys.” The ureteropelvic junction (UPJ) is the area where the ureter joins the renal pelvis. It is a common site of obstruction of the outward flow of urine from the kidney.

The hilum (pl. hila) is the location on the kidney where the ureter and renal vein leave the kidney and the renal artery enters. The cortex contains tissue with millions of microscopic units called nephrons (Fig. 6-4). Here in the tiny nephrons, blood passes through a continuous system of urinary filtration, reabsorption, and secretion that measures, monitors, and adjusts the levels of substances in the extracellular fluid.

14. transurethral ____________________________________________________________________________________

15. paranephric _____________________________________________________________________________________

16. retroperitoneal __________________________________________________________________________________

17. suprarenal ______________________________________________________________________________________

18. perivesical ______________________________________________________________________________________