4.- The Circulatory System - Organs And Functions

Organs And Functions:

1. The Heart: Is the organ responsible for pumping blood throughout the body. This consists of four spaces, two ventricles and two atria. The heart beats and contracts 70 times per minute, depending on the age and physical effort.

2. Blood Vessels: Allow blood to flow quickly from one body part to another and then back to the heart. You can increase its size depends on the blood that passes through it. There are three types of blood vessels:

- Arteries: Carry oxygenated blood from the heart.
- Veins: Carry blood back to the heart.
- Capillaries: Are small blood vessels that form a connection between the arteries and veins.

3. Blood: Our body has about 4 to 5litros blood. The heart pumps blood to the whole body and transported hormones, nutrients, oxygen, antibodies ... they need to keep the body.
Blood is composed of different cells:

- Red cells: They represent 45% of blood volume. The mother cell reproduces around 2 million cells every second.
- White blood cells: They represent a small percentage of the number of cells in the blood. Protect the body from disease.
- Platelets: Are cells responsible for blood clotting. They help stop bleeding. For example if we cut, platelets accumulate where it is cut and plug dl hole to stop the bleeding.

Webgraphy:

http://www.innerbody.com/image/cardov.html

http://www.newhealthadvisor.com/Circulatory-System-Organs.html

http://www.healthline.com/human-body-maps/circulatory-system