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Simplifying the most complex machine – human body

No one can claim to have mastered the understanding of human body – the most complex machine. But we are are lucky to be owning one each. Buy a new mobile handset and you would try to explore it going through its manual or by playing with its features. Got a bike or car and you would ensure not missing its regular service. We are so careful about the simple gadgets that we would try our best to get then checked regularly so that we don’t lose them. Do we bother to know about our own body? Do we get our body checked regularly just to be sure that all our organs are in good condition? Probably not many of us do that.

Isn’t it ironic that we don’t care much about this most complex machine. Probably just because we got it for free.

Lets start from knowing about our own body. I would try to keep it simple as possible without boasting about lot of medical terminologies.

What is a human body made of?

Human body simply consists of number of organs like brain, heart, kidneys, liver etc. each having its specific role that most of you are aware of. Each of these organs is actually a very complex machine and we haven’t been yet able to replicate any of these. Just like a mobile handset has plastic, glass, steel etc. each organ would have number of component, let’s call them as tissues. Now we know that steel is basically made up of carbon atoms, atoms being the basic unit. Similarly “Cell” is the basic unit of every tissue.

Where does the body get energy from?

We know that most of the machines that we use today work on electrical energy. In a  fan this electrical energy is converted into mechanical energy that moves the blades of fan. The human body works on a specific energy that in the form of ATPs. The body produces energy in the form of ATPs and the same is used for every activity. You would be surprised to know that the major portion of our daily energy requirements is for the activities that we never notice. That is called as basal metabolic rate (BMR). This is the amount of energy that our body requires daily even if we are sleeping for the whole day and night. This is the energy consumed in activities like breathing, pumping of heart, digestion of food and even for thinking. Every cell of human body needs energy for executing the task it’s supposed to do.

The basic source of energy (ATPs) is intracellular metabolism of glucose. After entering the cell every molecule of glucose gets metabolised to CO2 and water and during the process ATPs are released. For metabolism of glucose the cells require oxygen (O2) and for entry of glucose inside a cell every molecule requires one molecule of insulin too.

How to various body organs connect with each other? 

From the above discussion you must have understood that for the body to function glucose must reach every cell in addition to oxygen. Also the CO2 generated during this process must be thrown out. This job is done by circulatory system which is like the transport system. There are large vessels (just like big highways) that leave from heart and keep on dividing up to the level of minute capillaries (similar to the narrowest gali). Blood getting pumped from heart reaches each and every capillary of the body. Capillaries are surrounded by cells. The cells take up nutrients like glucose and oxygen from capillaries in exchange of CO2 and other waste material. The waste material from there reaches back to heart through venous system. The transport system of human body is strictly one way. The blood from heart reaches organs through Arteries and from there it goes back to heart through Veins.

Waste material disposal in the body

Gaseous wastes are disposed off through lungs. We take up air while breathing in, the air reaches millions of alveoli (in the lung) and the exchange of gases between alveoli and capillaries (small blood vessels) happens here. The oxygen enters inside blood and carbon dioxide earlier generated by the cells is thrown out. So we take up oxygen from air and release carbon dioxide with each breathing. Similarly in the kidneys the basic unit is glomerulus again a microfilter where waste material are thrown out of blood and drained out of body through urine.

What are the other systems of body? 

The transport system starting from and ending on heart which is the pumping organ as described above is called circulatory system. The gaseous filtering through lungs is called respiratory system. The waste disposal thorough kidneys is called urinary system. The 2 most important systems not discussed till now are gastrointestinal system and nervous system. Nervous system is like the CPU (that job is done by brain) and various cables coming out from CPU (nerves) that connect to all other organs of body. Gastrointestinals system is for digestion of food that we consume. Whatever we eat goes through a lengthy intestinal tract in which most of the consumed food is digested and absorbed by capillaries to be added to blood. Waste material is excreted through anus.

Where do the cells get glucose from?

Food that we consume basically has 3 types of nutrients – carbohydrates, proteins and fats. After consumption the food passes through a lengthy intestinal tract and gets digested during the transit. By the time it reaches small intestine, carbohydrates are broken down to glucose, proteins get broken down to amino acids and fats get broken down to fatty acids. All these are absorbed by the small blood vessels (capillaries) surrounding the intestine and reach the blood. Now blood acts as a transport system to carry these nutrients to all the cells of the body.

You must be wondering if the cells need only glucose, why are fatty acids and proteins absorbed at all. Proteins are basically the building blocks of our body. Each organ is made of proteins. Proteins are like the metal and plastic thats needed for making a motorcycle while glucose is like the petrol it needs to run. Fats basically act as the reserve fuel and are stored largely beneath our skin and in abdomen (tummy) as reserve food to be used while we are starving.


In summary it would suffice to say that glucose and oxygen are the basic necessities of every organ of human body and the task is accomplished by gastrointestinal system (digestion and absorption), circulatory system (transportation) and respiratory system (exchange of gases).

Having understood these basics, you would find it very useful to understand future articles on major health issues like obesity, diabetes, heart problems etc. Subscribe to the blog and stay tuned on social media for upcoming articles.

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