The Heart

The heart is one of the most important organs in the body as it delivers oxygenated blood (blood exposed to oxygen from the lungs) to our cells, allowing them to respire and release energy. This lets us move around and survive.

The heart consists of many parts which work together to make it perform efficiently. Here are the functions of these parts:

  • The Vena Cava: A vein that carries deoxygenated blood from our body to the right atrium. The superior vena cava carries blood coming from the upper parts of the body and the inferior vena cava carries blood from the lower parts of our body.
  • Aorta: An artery that carries around oxygenated blood from the left ventricle to the rest of the body. It is very powerful since the blood needs to reach the whole body.
  • Pulmonary Artery: An artery that carries deoxygenated blood from the right ventricle to the lungs to become oxygenated.
  • Pulmonary Vein: A vein that carries oxygenated blood from the lungs to the left atrium.
  • Atria (singular: atrium): The two upper chambers of the heart.
  • Ventricles: The two lower chambers of the heart.
  • Valves: Tiny structures that act as flaps to prevent the backflow of blood in the heart.
  • Coronary Arteries and Veins: These blood vessels aren’t shown in the diagram below since they’re on the surface of the heart. The arteries provide the heart with oxygenated blood and the veins carry the blood back to the heart to send to the lungs.
Source: BioNinja. Here is a diagram of the inside of a human heart. This diagram is from the perspective of someone facing you so the structures are flipped around. That’s why the left ventricle and atrium is on the right side and the right ventricle and atrium on the left side.

There is a gas exchange between the blood in a capillary (a one-cell thick blood vessel) and an alveolus that’s close enough to it. Alveoli (the plural of alveolus) are tiny air sacks in the lungs that allow efficient gas-exchange. Oxygen diffuses into the blood and carbon dioxide diffuses out. The oxygen binds to the haemoglobin (a protein molecule) in red blood cells so that it can be carried around the body in the blood.

The blood travels to the heart and goes into the left atrium which then passes into the left ventricle without flowing backwards because of the valves in between the chambers. The blood then is pushed out of the aorta at a very high pressure so that it can effectively be delivered to all the parts of the body, including the heart itself.

Once all the blood is distributed and the body cells have taken up the oxygen for respiration, the blood comes back to the heart via veins. Blood from the upper body enters the heart through the superior vena cava and blood from the lower body enters through the inferior vena cava. The blood goes into the left atrium and is then pushed into the left ventricle. The blood then travels at a high pressure through the pulmonary artery which delivers deoxygenated blood back to the lungs to get more oxygen and get rid of carbon dioxide (a waste product of respiration that is diffused into the blood). The process repeats.

This system is known as a double circulatory system since there are two separate paths for blood to flow, one for oxygenated blood and the other for deoxygenated blood. The right ventricle and atrium deals with blood going to the lungs while the left ventricle and atrium manages blood going to the rest of the body. This makes the circulatory system even more efficient.

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