Excretion in human beings

Date: December 09, 2014

Excretion in Human Beings

The excretory system of human beings consists of two bean-shaped kidneys located in the abdomen. Two excretory tubes or ureters, one from each kidney, open into a urinary bladder. The urine collected in the urinary bladder passes into a muscular tube called urethra, from which it is thrown out through an opening at its end, the urinary opening.

Each kidney is made of excretory units called nephrons. Each nephron has a cup shaped upper end, called Bowman’s capsule containing bundle of capillaries called glomerulus. These blood capillaries arise from the artery, which brings waste and excess water from body to kidney. Bowman’s capsule leads into tubular structures.

The waste material along with blood is brought to kidneys by the renal arteries. Blood is filtered out from the blood capillaries into Bowman’s capsule. As this filtrate passes through the tubular parts of nephron. Useful products, such as glucose, amino acids are reabsorbed by blood capillaries surrounding the nephron. The nephrons drain the waste into a space inside kidney leading to the ureter. Human urine contains water and nitrogenous substances, most of which is urea. From the ureter, urine passes into the urinary bladder and is stored there till thrown out of the body.

Osmoregulation – osmoregulation, as the word suggests, is the process of regulating water content and in concentration in the body. Osmoregulation is related to the habitat of an animal. Fresh water animals take up large amount of water through their skin and mouth. They need to get rid of by frequent excretion of lot of urine. Marine animals and terrestrial animals, including humans, need to conserve water. For this, the excretory system is able to reabsorb water. Such reabsorption or removal of excessive water is under hormonal control. Thus, kidneys not only function to remove toxic waste, but also control water balance and levels of mineral ions in the body.

Renal failure and technology for survival – Though kidney failure isnot common, but somthimes kidney infection, injury to kidneys or restricted blood flow to kidneys result in kidney damage and malfunctioning. In order to clean the blood of metabolic wastes and to maintain normal levels of water and minral ions in body fluids, an ‘artificial kidney’ is employed. The procedure used in artificial kidney in place of normal is called dialysis.

A matching kidney from another person may also be transplanted.