Page 1 - 2. Circulatory system of human beings

SAI International School

Subject- Biology, Class-VII
Topic-Transportation and Excretion
Subtopic- Circulatory system in human beings
Lesson notes

BLOOD VESSELS:

• The blood in our body flows through vessels or tubes called blood vessels.
• Blood vessels are of three main types: Arteries, Veins and capillaries

ARTERIES
• Carry oxygenated blood from the heart to all the parts of the body.
• Pulmonary artery is an exception, because it carries deoxygenated blood from the heart
to the lungs for purification
• Have thick and elastic walls blood to withstand the high pressure of blood flowing
through them.
• No valves
• Deep seated in the body
• The largest artery in the human body is the aorta which.carries oxygen-rich blood from
the left ventricle of the heart to all parts of the body. It further branches into smaller
arteries that supply various organs.

VEINS
• Carry deoxygenated blood from all the parts of the body back to the heart.
• Pulmonary vein is an exception, because it carries oxygenated blood from the lungs to
the heart.
• They have thin walls
• Veins have valves to prevent the backflow of blood.
• Superficially located below the skin.

• The largest vein in the human body is the Vena Cava
• This vein carries deoxygenated blood from the body back to the right atrium of the
heart.
• The main vein Vena cava has two parts:

❖ Superior vena cava – collects blood from the upper body.
❖ Inferior vena cava – collects blood from the lower body.