The human circulatory system

In a nutshell

The circulatory system is the body's way of bringing the oxygen that is breathed in from the air into the body. It also removes carbon dioxide and circulates nutrients to muscles and organs.

Parts and functions of the circulatory system

The heart

The heart is a muscle that pumps blood around the body. It is the size of a closed fist and beats $60-90$ times a minute. It has four sections called chambers which allow blood rich in oxygen and carbon dioxide to be kept apart.

Blood vessels

Blood vessels are a network of tubes that blood travels in. There are three types you should know.

Science; Animals, including humans; KS2 Year 6; The human circulatory system

	Blood vessel	Function
1.	Arteries	Transport blood away from the heart to the body.
2.	Veins	Transport blood towards the heart.
3.	Capillaries	Tubes with thin walls that allow gases and nutrients to pass through.

Blood

Blood travels through blood vessels and carries cells, dissolved nutrients, and gases. There are four components of blood you should know.

Plasma	A liquid that carries cells and dissolved nutrients.
Red Blood Cells	Cells that carry oxygen or carbon dioxide. These cells also give blood its red colour.
White Blood Cell	Cells that fight infection.
Platelets	Cell pieces that help the blood to get sticky (clot) if there is damage.

Transport in the circulatory system

The human circulatory system helps to deliver nutrients, water, and oxygen to cells and tissues and carries away waste products like carbon dioxide.

Science; Animals, including humans; KS2 Year 6; The human circulatory system

1.	The heart pumps blood that is low in oxygen to the lungs through arteries.
2/3.	Oxygenated blood (blood rich in oxygen) flows back to the heart through veins.
4.	The heart pumps blood that is high in oxygen around the body to cells and tissues. Deoxygenated blood (blood low in oxygen) flows back to the heart through veins, carrying carbon dioxide from cells and tissues.