urinary system - Physiology, Role in disease, Testing

The physiological system involved in the production, storage, and excretion of urine. In mammals it consists of a pair of kidneys each connected to a muscular sac (the bladder) by a narrow fibromuscular tube (the ureter); a single urethra leaves the bladder to the exterior. Urine produced by the kidneys is temporarily stored in the bladder, then expelled via the urethra.

The urinary system is the organ system that produces, stores, and eliminates urine. In humans it includes two kidneys, two ureters, the urinary bladder, two sphincter muscles, and the urethra.

Physiology

Kidneys

The kidneys' are one of the various organs (together with the lungs, intestine and skin) that participates in the elimination of the wastes of the organism.

A kidney consists of about 1 million filtering units termed nephrons, each consisting of a glomerulus, ball-shaped network of capillaries, and a network of tubules.

Humans produce about 1.5 liters of urine over 24 hours, although this amount may vary according to circumstances. Increased fluid intake generally increases urine production, while increased perspiration and respiration may decrease the amount of fluid excreted through the kidneys.

The kidney plays a crucial role in regulating electrolytes in the human blood (e.g.

Ureters

Urine is collected in the renal pelvis (or pyelum), which connects to the ureters, which carry urine to the bladder. Small amounts of urine are emptied into the bladder from the ureters about every 10 to 15 seconds.

Bladder

The urinary bladder is a hollow muscular organ shaped like a balloon.

The bladder stores urine; It allows the bladder to stretch to accommodate urine without rupturing the tissue.

Sphincters (circular muscles) regulate the flow of urine from the bladder. The bladder itself has a muscular layer (detrusor muscle) that, when contracted, increases pressure on the bladder and creates urinary flow.

Urination is a conscious process, generally initiated by stretch receptors in the bladder wall which signal to the brain that the bladder is full. When urination is initiated, the sphincter relaxes and the detrusor muscle contracts, producing urinary flow.

Role in disease

Kidney diseases are normally investigated and treated by nephrologists, while the specialism of urology deals with problems in the other organs.

Diseases affecting the urinary system:

There are numerous kidney diseases, many of which interfere with the normal production of urine. Stenosis (blockage), reflux (backflow of urine into the kidney, causing damage) Urinary tract infections (UTIs), interstitial cystitis, incontinence (involuntary loss of urine), benign prostatic hyperplasia, prostatitis (inflammation of the prostate) and urinary retention (inability to pass urine). Bladder cancer, kidney cancer, and prostate cancer are examples of neoplasms affecting the urinary system.

The term "uropathy" refers to a disease of the urinary tract, while "nephropathy" refers to a disease of the kidney.

Testing

Urinalysis is a test that studies the content of urine for abnormal substances such as protein or signs of infection.

Urodynamic tests evaluate the storage of urine in the bladder and the flow of urine from the bladder through the urethra.

Ultrasound is commonly performed to investigate problems of the kidney and/or urinary tract.