4. What structures make up the human circulatory system?


The human circulatory system is made up of 3 parts that work together to move oxygen, glucose, nutrients and other chemicals to where they are needed. These 3 parts are: 1) the heart, 2) blood vessels, 3) blood.

The heart is a 4-chambered pump that pushes blood around the body. The heart has 2 sides: left and right. The left side is larger than the right and has thicker muscle making up the walls. This is because it has to pump blood around the whole body, whereas the right side only needs to pump blood to the lungs which are only a short distance away.

In each side blood moves from the top chamber (atrium) to the bottom chamber (ventricle) through a valve. No blood mixes between the left and the right sides of the heart as there is a thick wall separating the two, called the septum.

There are 3 types of blood vessels: the arteries (that move blood away from the heart), the veins (that move blood towards the heart) and the capillaries (very thin tubes that connect the arteries to the veins). The capillaries travel close by every cell in the body so oxygen, glucose and nutrients can be dropped off to be used by the cells.

Blood is the third part that makes up the circulatory system. Blood is made of a liquid called plasma and blood cells. There are 3 types of blood cells: red blood cells that carry around oxygen, white blood cells that prevent disease and platelets that helps the blood to clot and stop the bleeding from a cut.


Artery: Large and thick muscular blood vessel that transports blood away from the heart.

Atrium: Chambers at the top of the heart. Receives blood from the lungs (left) or the body (right).

Blood vessel: Tubes that transport blood.

Capillary: Tiny blood vessel in organs that connect arteries to veins.

Heart: Muscle that pumps blood around the body.

Plasma: Liquid component of blood.

Platelets: Cells that help blood clot.

Red blood cells: Cells that transport oxygen and carbon dioxide around the body.

Septum: Thick wall that separates the left and right sides of the heart.

Vein: Large and thin blood vessel that transport blood towards the heart.

Ventricle: Chambers at the base of the heart. Pumps blood to the lungs (right) or the rest of the body (left).

White blood cells: Cells that protect the body from infection.