CIRCULATORY SYSTEM
In all living organisms, nutrients and waste substances are transported through the body thanks to the circulatory system. In vertebrates, blood moves through the entire body via blood vessels, to distribute oxygen and nutrients to the cells needed to perform our vital functions.
In the case of plants, circulation of water and minerals is conducted by ducts called the xylem and circulation of food (sugar) is transported by the ducts called the phloem.
Blood vessels
Blood vessels are tubes through which blood circulates. They are classified in arteries (carrying blood with oxygen), veins (carrying blood with carbon dioxide) and capillaries (delivering oxygen and nutrients to the cells).
The blood
This is a tissue in a liquid state. It is formed by plasma (made up of water and nutrients) and blood cells (composed of red blood cells, white blood cells and platelets).
Blood circulation
It has two phases: general or greater circulation, and pulmonary or lesser circulation. The first is the journey that the blood makes throughout the body. The second is the journey of blood between the heart and the lungs.
Circulation in human beings
Human beings have a circulatory system that consists of the heart, blood vessels and blood. Its function is to transport to all the cells the oxygen and nutrients the body needs, as well as to circulate and remove wastes.
The heart
This is a muscular, inverted cone-shaped organ, the size of a fist, located in the center of the chest, between the lungs. It functions as a pump that pushes blood to all parts of the body.
It is divided into four cavities: two upper cavities (atriums) where the blood arrives and two lower cavities (ventricles) where the blood passes before being pumped all around the body in arteries.
Pulmonary circulation
All the blood the veins, loaded with CO2, enters the right atrium, passes to the right ventricle and reaches the lungs through the pulmonary artery. Then, blood is oxygenated through the pulmonary veins, comes out of the lungs, goes to the left atrium into the left ventricle and out through the aorta (the main artery of the body).
Systemic circulation
The oxygen-rich blood that leaves the heart through the aorta is pumped to all the arteries of the body giving nutrients received from the digestive system and oxygen absorbed by the lungs to all the body’s organs.
