Kidneys

Kidneys viewed from behind with spine removed. The kidney is one of the various organs together with the lungs, intestine and skin that participates in the elimination of the wastes of the organism. The kidneys bean-shaped organs about the sie of a human fist. They are near the middle of the spine, just below the ribcage.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. Blood is filtered bhe glomerulus, and the resultant "prourine" passes through the tubular system where water, electrolytes and nutrients are reabsorbed.

Humans produce about 1.5 liters of urine over 24 hours, although this amount may vary according to the circumstances. Increased fluid intake generally increases urine production, while increase perspiration and respiration may decrease th amount of fluid excreted through the kidneys. Some medications interfere directly or indirectly with urine production, such as diuretics.The kidney plays a crucial role in regulating electrolytes in the human blood . sodium, potassium, calcium. In addition, it clears urea, a nitrogenous waste product from the metabolism of amino acids

Ureters
Urine is collected in the renal pelvis which connects to the ureters, which carry urine to the bladder. The ureters are about 8 to 10 inches mm long. Smooth muscular tissue in the walls of the ureters peristaltically force the urine downward. Small amounts of urine are emptied into the bladder from the ureters about every 10 to 15 secnds.
BladderThe urinary bladder is a hollow muscular organ shaped like a balloon. It is located in the pelvic fossa and held in place by ligaments attached to the pelvic bones.hebladder stores urine; it swells into a rund shape when it is full and gets smaller when empty. In the absence of bladder disease, it can holdupto 16 fluid ounces of urine comfortably for 2 to 5 hours.Sphincters regulate the flow of urine from the bladder. The bladder itself has a muscular layer derusor muscl tat, when contracted, increasespressure on the bladder and creates urinary flow.Urination is a concious process, generally initiated by stretch receptors in the bladder wall which signal to the brain that the bladder is full. This is felt as an urge to urinate. 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. Gynecologists may deal with problems of incontinence in women.Diseases affecting the urinary system:There are numerous kidney diseases, many of which interere with the norml production of urine. Renal failure may be acute or chrnic, and may require medication and dialysis.
Kidney stones may be painful and cause long-term kidney damage. Proteinuria is usually without symptoms but may indicate renal disease.
Stenosis blockage, reflux backflow of urine into the kidney, causing damage
Urinary tract infections inerstitial cystitis, incntinence benign prostatic hyperplasia, prostatitisinflammation of the prostate and urinary retention (inability to pass urine.

Testing
Urinalysis is a test that studies the content of urine for abnormal substances such as protein or signs of infection. This test involves urinating into a special container ad leaving the sample to be studied.Urodynamic tsts evaluate the storage of urie in the bladder and the flow of urine from the bladder throug the urethra. It may be performed in cases of incontinence or neurological problems affecting the urinary tract.Ultrasound is commonly performed to investigate problems of the kidney and/or urinary tract. UB is plain radiography of the urinary system, e.g. to identify kidney stones. An intravenous pyelogram studies the shape of the urinary system.