The Circulatory System: blood, vessels and the heart

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The Circulatory System

Blood Red blood cells

Haemoglobin - red, carries oxygen

Disc shaped, thinner at the centre

No Nucleus

White blood cells

Contain a nucleus

No definitive shape

Protect against disease

Platelets

Tiny fragments of cells

No nucleus

Cause blood to clot

Functions of blood

Transport

Defence against disease

Blood Vessels Artery

Carry blood from the heart

Narrow lumen

Thick walls

High Pressure (Fast movement of blood)

No valves

Vein

Carry blood back to the heart

Wider lumen

Thinner walls

Low Pressure (Slow movement of blood)

Valves to stop back-flow of blood

Capillary

Tiny blood vessels

Walls one cell thick

Substances pass into blood through capillaries

The Heart

Blood enters through the Vena cava to the Right atrium

Is pumped through the pulmonary artery to the lungs

Returns from the lungs in the Pulmonary vein

Is pumped around the body through the aorta

Valves prevent blood from flowing backwards

Normal heartbeat rate is 70bpm

Increases during exercise as the body needs more energy.

Normal body temperature is 37° Celsius