We will discuss here about the importance of excretion and some other excretory organs.
We take three types of food protein, carbohydrate and fat. By the catabolism of protein a compound is formed in our body, called ammonia. This harmful toxic material is then modified into urea. It is the main excretory material of human body, which is excreted through urine.
During filtration of blood some essential components also go out from it along with the excretory materials. These include sugars, proteins, essential salts and water. But nephrons send those components back to blood. This is called reabsorption. It is an essential process for our body. Everyday human kidneys separate about 170 litres of filtrate from blood, of which only 1.5 litres are passed out as urine. Remaining water and essential components are reabsorbed into blood to maintain salt and water balance of the body.
Besides kidney some other excretory organs take part in the removal of excretory substances. These are skin, lungs and liver. Sweat comes out through sweat glands of our skin. Through skin some Lungs excretory materials, excess salt and water goes out from our body in the form of sweat. Through lungs we release carbon dioxide; liver helps us to get rid of some unwanted metals and toxic substances.