The Circulatory System

To carry digested food from the small intestine to all areas in the body which need it.

To carry oxygen from the lungs to the rest of the body.

To aid in the disposal of all wastes from the body.

To distribute heat. To fight diseases by using white blood

cells to fight off infection.

The blood is made up of different types of cells and a liquid medium for which they are transported.

The cells in the blood are Red Blood Cell (Corpuscles), White Blood Cells and Platelets.

Plasma is the liquid medium of blood. Red Blood Corpuscles are technically not

cells at all, as they do not contain a nucleus. Their red colour is from a substance known

as haemoglobin. Haemoglobin binds with oxygen so it is the

red blood corpuscles that carry oxygen in the body.

White Blood Cells are largest and not as plentiful in the blood as corpuscles.

These cells are used to fight infection. Foreign bodies are either devoured by the

cells or the cells produces antibodies, which in turn attack the infection.

Platelets are small fragments of cells, and are responsible for blood clotting.

A Haemophiliac (someone who cannot clot) doesn’t have any platelets.

Plasma is the medium in which all the cells are maintained.

It contain water, proteins (fibrinogen), food, wastes (e.g. CO2), Antibodies and Hormones.

The heart is a four-chambered hollow muscle, used to pump blood all over our bodies.

It is divided into four compartments, the left and right ventricles and the left and right atria (atrium in singular).

The right side of the heart pumps blood low in oxygen (de – oxygenated) to the lungs.

The left side of the heart pumps blood rich in O2 (oxygenated blood) all over the body.

Blood enters the heart through the superior and inferior Vena Cava and into the right atrium.

The tricuspid valve opens and the blood is moved into the right ventricle.

The walls of the right ventricle contract and the blood is pumped up to the lungs (through the pulmonary artery) where oxygen replaces CO2 in the blood.

The oxygenated blood enters the heart from the lungs through the left atrium (via the pulmonary vein).

Again a valve opens and the blood moved into the left ventricle.

The walls of the ventricle contract and the blood is pumped all over the body via the Aorta.

The rate of beat is controlled by the pace maker in the septum.

Arteries: Carry blood away from the heart always. Have thick muscular walls Have a pulse Deep under the skin Have no valvesVeins: Carry blood to the heart. Have thin walls Do not have a pulse Near surface of the skin Have valves to stop back-flow of blood. Capillaries are small blood vessels acting as veins

and arteries. The walls of capillaries are only one cell thick so

substances (Food or cells) can easily get through them and into the blood or out.

The Hepatic portal system is a transport system between the small intestine, the liver and the heart.

It consists of the hepatic portal vein, the hepatic artery and the hepatic vein.

The hepatic artery carries oxygenated blood to the liver for use and the collection of wastes.

The hepatic vein carries the used blood back to the heart.

The Hepatic Portal Vein carries blood from the small intestine to the liver.

This blood is low in O2 but rich in Glucose and other food types.

The Glucose is converted to Glycogen in the Liver and stored there.

Hypertension (or high blood pressure) is

caused by the blood vessels becoming narrow

because of the build up of fat or from stress. The heart therefore needs to pump harder to

get the blood through the narrow vessels. This can cause the left ventricle to grow, and

can lead to the heart not functioning properly.

The heart also needs a supply of blood and

gets from the coronary arteries. If these arteries get blocked, a heart

attack occurs. A stroke is caused by a blockage or leak

of blood vessels in the brain. Every year in Ireland, 10,000 people die of

heart attack or stroke.

The risks factors of heart attack and stroke are:

Smoking – nicotine can also block the arteries.

Obesity – more fat deposits in the blood vessels

Regular exercise can reduce the risk of heart disease.

Stress increases the risk of heart attacks.