Circulatory System

The circulatory system is a vast network of organs and vessels that is responsible for the flow of blood, nutrients, hormones, oxygen and other gases to and from cells.             

  Description and components of the circulatory system

The circulatory system is made up of three independent systems that work together: the heart (cardiovascular); lungs (pulmonary); and arteries, veins, coronary and portal vessels (systemic),

The heart, blood, and blood vessels make up the cardiovascular component of the circulatory system.

It includes the pulmonary circulation, a "loop" through the lungs where blood is oxygenated. It also incorporates the systemic circulation, which runs through the rest of the body to provide oxygenated blood.

The pulmonary circulatory system sends oxygen-depleted blood away from the heart through the pulmonary artery to the lungs and returns oxygenated blood to the heart through the pulmonary veins.

Blood Basics

Two types of blood vessels carry blood throughout our bodies:

1. Arteries carry oxygenated blood (blood that has received oxygen from the lungs) from the heart to the rest of the body.
2. Blood then travels through veins back to the heart and lungs, so it can get more oxygen to send back to the body via the arteries.

The blood that flows through this network of veins and arteries is whole blood, which contains three types of blood cells:

1. red blood cells (RBCs)
2. white blood cells (WBCs)
3. platelets        

                          

• More than half of blood is plasma. This is a clear, pale yellow liquid, which carries all the blood cells and platelets and chemicals such as hormones and glucose.
• Red blood cells are responsible for carrying oxygen round the body, and collecting carbon dioxide and taking it back to the lungs where it can be breathed out.
  • There are millions of red blood cells in one small drop of blood.
  • These cells are red because they hold a red coloured chemical called haemoglobin.

• White blood cells act as the defenders of the body against germs or foreign bodies.
  • The white blood cells work with special proteins called antibodies, which also travel in the blood.
  
  
  • The platelets are sticky little cells that move around in the blood until a blood vessel is injured in some way (when bleeding starts).

THE  HEART

The heart is really a muscle. It's located a little to the left of the middle of the chest, and it's about the size of your fist. There are lots of muscles all over the body — in the arms, in the legs ... but the heart muscle is special because of what it does. The heart sends blood around the body. The blood is sort of like a pump, or two pumps in one. The right side of the heart receives blood from the body and pumps it to the lungs. The left side of the heart does the exact opposite: It receives blood from the lungs and pumps it out to the body.