How the healthy body functions?
The functioning of the human body has been compared to all manner of machines, but the reality is that no machine ever invented or designed comes close to the huge complexity that is man or woman. Every second of the day, in billions of individual cells in the body, a vast array of chemical, electrical and mechanical reactions are taking place without a hitch, allowing us to go about our daily lives. Power supply Probably the most important feature that distinguishes the body from mere machines is its ability, through the reproductive organs, to produce children. However, in some respects, the way the body works has some passing similarities to machines, in that certain functions are common to both. Without power, most machines would cease to function, and there is no doubt that this is the case for the human body. Basic requirements Two essential elements are required for life - nutrients and oxygen - and if either were in limited supply for any length of time, the body would die. The body requires nourishment to fuel the many chemical reactions taking place within the body, and to maintain and build new cells, replacing those that die off each day. Food and drink are processed by the digestive system and absorbed into the body, providing the nutrients and water that must be present for life to continue. Equally essential for life, oxygen from air is breathed in via the respiratory system and transported to the lungs, where it is absorbed into the surrounding blood vessels. Circulatory transport The presence of food in the stomach and air in the lungs would be of no consequence without a means of conveying them to the parts of the body where they are needed. The heart and blood vessels form a transport network that supplies oxygen and nutrients to the tissues, collections of specialized cells that perform certain functions in the body. Blood rich in oxygen from the lungs reaches the heart, which pumps it around the body, picking up nutrients absorbed from the digestive system on the way. Blood then returns to the heart and is transported to the lungs to have its oxygen levels topped up. Like all machines, there are waste products and poisons produced as fuel and oxygen are consumed. Unused food products leave the digestive system in the form of faeces. By products of chemical processes in the cells, such as carbon dioxide, are removed via the bloodstream and breathed out though the lungs. Other chemicals in the blood are filtered out by the kidneys, and removed from the body as urine. Complex activities The human body gathers information about its environment through the sense organs - the eyes, ears, nose, taste receptors on the tongue and touch sensors in the skin. This information is conveyed through a hugely complex system of nerves to the body's control centre, the brain. The brain is the seat of conscious thought, emotion, memory and countless other functions, such as coordinating movement through the bones, muscles and joints. The brain is also responsible for many bodily functions that are automatic and beyond conscious control, such as sweating. This is often in association with the endocrine system, a series of glands that communicate through chemical messengers called hormones. The human body also has a built-in security system, designed to repel germ and chemical warfare. It has physical and chemical barriers at the entrance to the digestive and respiratory systems, in addition to the protective skin. There is also the internal immune system, a highly efficient destroyer of all manner of bacteria and viruses. |
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