P.E - The Circulatory System

The three components are:

• The heart
• Blood Vessels
• Blood

It is a double circulatory system, it comprises two seperate circuits and blood passes through the heart twice.

The pulmonary curcuit carries blood to the lungs to be oxygenated and then back to the heart. In the lungs, carbon dioxide is removed from the blood, and oxygen taken up by the haemoglobin in the red blood cells.

The systemic curcuit carries blood around the body to deliver the oxygen and returns de-oxygenated blood to the heart. Blood also carries nutrients and waste

The heart is seen from the front. So the right side of the heart is shown on the left of the diagram. The left side is on the right side of the diagram.

The heart is a muscular pump. When it beats it pumps blood to the lungs and around the body. The amount of blood pumped can be calculated:

Heart rate x stroke volume = cardiac output

These increase when exercising.

The heart has four chambers. The two atria collect the blood. The two ventricles pump the blood out of the heart.

Valves prevent the blood from flowing backwards.

The septum seperates the two sides of the heart.

The right side of the heart pumps de-oxygenated blood (blood not containing oxygen) to the lungs to pick up oxygen. The left side of the heart pumps the oxygenated blood from the lungs around the rest of the body.

There are three types of blood vessel:

Arteries

• Carry blood away from the heart (always oxygenated apart from the pulmonary artery which goes to the lungs)
• Have thick muscular walls
• Have small passageways for blood (internal lumen)
• Contain blood under high pressure

Veins

• Carry blood away from the heart (always de-oxygenated apart from the pulmonary artery which goes from the lungs to the heart)
• Have thin walls
• Have larger internal lumen
• Contain blood under low pressure
• Have valves to prevent blood flowing backwards

Capillaries

• Found in the muscles and lungs
• Microscopic - one cell thick
• Very low blood pressure
• Where gas exchange takes place. Oxygen passes through the capillary wall and into the tissues, carbon dioxide passes from the tissues into the blood.

Blood has four key components:

Plasma

• Fluid part of blood
• Carries carbon dioxide, hormones and waste

Red blood cells

• Contain haemoglobin with carries oxygen
• Made in bone marrow. The more you train the more red blood cells are made.

White blood cells

• Protect the body by fighting disease
• Made in the long bones

Platelets

• Clump together the form clots
• Protect the body by stopping bleeding

When exercising blood does the following things:

• Transports nutrients and waste
• Delivers oxygen to the working muscles
• Removes heat (temperature regulation)
• Dilutes/carries away lactic acid (acidic balance)

Blood pressure increases when you exercise, but is lower at rest when you are fit. It is also affected by age, smoking, stress, diet and weight.