We all obtain our nutrients from different sources which are later digested and metabolized in our body. After metabolic reactions, the body starts to sort out useful and toxic substances in an individual. As we all knew, the accumulation of the toxins may be harmful. Thus, the body removes all the metabolic wastes by the process called excretion. Different organisms follow different modes of excretion. Let’s take a glance at excretion process in humans and the human excretory system.
Human excretory system
Elimination of toxic and waste products from the body is called excretion. Most of the unicellular organisms eliminate waste from their body through diffusion. A human body is an exceptional machine where a lot of processes (respiration, circulation, digestion, etc.) take place simultaneously. As a result, a lot of waste products produced in our body are in different forms that include carbon dioxide, water, and nitrogenous products like urea, ammonia, and uric acid. In addition to these, the chemicals and other toxic compounds from medications and hormonal products are also produced. A simple diffusion or evaporation will not be sufficient to eliminate the waste from our body.
In complex organisms such as animals, including humans, there is a specialized system for excretion called the excretory system. A human excretory system consists of a couple of kidneys and ureters, a urinary bladder, and a urethra.
Blood contains both useful and harmful substances. Hence, we have kidneys which separate useful substances by reabsorption and toxic substances by producing urine. Kidney has a structural filtration unit called nephron where the blood is filtered. Each kidney contains a million of nephrons. Capillaries of kidneys filter the blood and the essential substances like glucose, amino acids, salts, and required amount of water are reabsorbed. Meanwhile, the pure blood circulates back to other parts. The nitrogenous and other waste products and excess water are converted to urine.Urine thus produced is passed to the urinary bladder via the ureters. The urinary bladder is under the control of Central Nervous System. The brain signals the urinary bladder to contract and through the urinary opening called urethra, we excrete the urine.
Under certain circumstances such as poor blood flow to the kidneys, infections, injuries, etc. the kidneys fail to perform their functions. In such situations, artificial kidneys are used for blood filtration and this process is called as dialysis.
Other than the urinary system, skin, lungs, and even eyes helps in excreting waste products in different forms. Sweating is a mode of excretion where water, urea, and other salts are excreted through the skin. Lungs help us to exhale gaseous wastes such as carbon dioxide, nitrogen, etc.