What makes the kidney and urinary tract?
Urinary tract comprises of two kidneys, ureters, bladder and urethra.
Kidneys are two bean shaped organs located in abdominal cavity under the rib cage. They filter the blood to clear the impurities and waste products in the form of urine.
The ureters are tubular structures that transport the urine from kidneys to bladder. The formation of urine and its passage to bladder is not under voluntary control.
Bladder is a bag of muscle which distends and stores the urine till it is discharged outside through the urethra from time to time. The capacity of bladder increases with age. The voluntary control of bladder function also matures with age.
The normal urine frequency is 15-20 times in a newborn baby. It decreases to normal adult frequency of 5-8 times in daytime by 5 years of age.
How does a kidney function?
A kidney is composed of millions of fine tubules called as nephron, the functional unit of kidney. Each nephron has different segments, each with specialized function.
Blood is filtered at the nephron and larger molecules like blood cells and proteins are retained in the blood. This filtrate is further modified as it passes through different nephron segments and the useful molecules are absorbed back into the blood and impurities are discarded in the form of urine.
The amount of urine produced increases with age and it also depends on amount of water intake and losses through sweating etc.
Kidneys have a large capacity to alter the urine composition in order to maintain the water balance and chemical composition of body in a tight range, which in turn is important for proper functioning of different organ systems like heart, brain, liver, muscle etc. Therefore kidneys are vital to body’s proper functioning.
What are other functions of kidneys?
Kidneys also produce a hormone known as Erythropoietin (EPO) which stimulates the bone marrow to produce red blood cells.
Kidneys convert Vitamin D produced in skin on sun-exposure to its active form and help in keeping bones healthy.