The Circulatory System

The circulatory system is the vital organ system that transports blood into the whole body. It consists of the heart and many blood vessels. The blood vessels are subdivided into two categories: the arteries, which lead the blood away from the heart, and the veins, which lead the blood to the heart. The arteries mostly contain oxygenated blood, while the blood that circulates through the veins isn't mostly oxygenated. There are also the capillaries, very thin blood vessels used to access even the most isolated cell of our body.

Our bodies have two different circulations: systemic circulation and pulmonary circulation. Systemic circulation is a circuit loop that delivers oxygenated blood from the heart to the cells of our body. The oxygenated blood comes from the lungs to the left heart and is afterward pumped into the rest of the body. The blood then gives vital oxygen to the cells and receives carbon dioxide. The carbon dioxide is led through the veins to the right heart, where it's pumped into the pulmonary circulation. The arteries of the pulmonary circulation lead the blood without oxygen to the lungs, where carbon dioxide is taken from the blood and oxygen is inserted. The veins lead the now oxygenated blood to the right heart and everything is repeated. These two circulations are vital to us.

Systemic circulation:

- Arteries --> oxygenated blood

- Veins --> blood without oxygen

Pulmonary circulation:

- Arteries --> blood without oxygen

- Veins --> oxygenated blood

Cellular respiration

Cellular respiration is the process by which organisms use oxygen and foodstuff to avert the energy in these substances into vital activities and to get rid of waste products (carbon dioxide and water.)

The energy released during the process of breaking down glucose, carbohydrates, fats, and other organic fuel during glycolysis is stored in adenosine triphosphate . Pyruvate molecules produced during glycolysis then enter the mitochondria, where they are converted into acetyl coenzyme A. This compound enters the TCA cycle.

The TCA cycle, also known as the Krebs cycle, is very important in the process of breaking down organic fuel molecules. The cycle is subdivided into eight stages with eight different enzymes that produce energy. Most of the energy is captured and later converted into ATP, which will later be used as a source of energy for our cells. The waste product carbon dioxide is released into the blood and is transported to the lungs to be eliminated. Then the whole process enters the last stage, where electrons are added to oxygen, which leads to the formation of ATP and water as a waste product.

Composition of blood