THE CIRCULATORY SYSTEM THE ADULT HUMAN BODY CONTAINS ONLY ABOUT 5 LITRES OF BLOOD © PDST Home Economics

COMPOSITION OF THE BLOOD BLOOD IS MADE UP OF: A LIQUID PART CALLED PLASMA 2. CELLS THAT ARE SUSPENDED IN THE PLASMA

COMPOSITION OF THE BLOOD THE PLASMA IS MADE UP OF: 90% WATER 2. There are many substances dissolved in the water, e.g. Sugar, Protein, Hormones, Enzymes, Minerals etc.

COMPOSITION OF THE BLOOD THERE ARE 3 TYPES OF CELLS SUSPENDED IN THE PLASMA: RED BLOOD CELLS 2. WHITE BLOOD CELLS 3. PLATELETS

Functions of the Blood THE BLOOD HAS THREE MAIN FUNCTIONS: TRANSPORT 2. FIGHTING INFECTION 3. CLOTTING

TRANSPORT: The blood carries very many substances around the body. For example: Blood carries oxygen from the lungs to the cells. Blood carries carbon dio0xide from the cells to the lungs.

Blood carries digested food products from the intestines to the cells. Blood carries waste from the cells to the liver and the kidneys. Blood carries hormones and enzymes around the body.

FIGHTING INFECTION: The blood destroys bacteria, and viruses that may infect the body.

CLOTTING: Sometimes a tear occurs in a blood vessel e.g. when you are cut Blood will leak out Infection may enter It is vital that such tears are repaired quickly The blood does this by forming a clot that seals the wound

Another function of the blood is to help maintain normal body temperature. THIS IS 37° C

The function of red blood cells is to carry oxygen around the body

The function of white blood cells is to fight infection

Some white blood cells produce substances called antibodies that identify and destroy bacteria, viruses Other white blood cells kill bacteria by engulfing them and digesting.

The function of the platelets is to help the blood to clot.

THE CIRCULATORY SYSTEM On leaving the heart, the blood passes into all of the organs and limbs of the body before being returned to the heart.

The Circulatory System

THE HEART The heart is located in the centre of the chest, behind the breast bone. The function of the heart is to pump blood. The heart is made up of muscle called cardiac muscle.

The Structure of the Heart The heart is divided into two sides, left and right, separated by a wall of muscle called the septum. Each side has two chambers. The top chambers are called atria. The lower chambers are called ventricles.

THE HEART left atrium right atrium left ventricle right ventricle septum THE FOUR CHAMBERS OF THE HEART

The heart acts as if it were two separate pumps: The right ventricle pumps blood to the lungs. 2. The left ventricle pumps blood all round the rest of the body.

Since the lungs are very close to the heart, the right ventricle doesn`t pump blood very far. Since it must pump blood much further, the muscle of the left ventricle is much thicker than of the right ventricle.

BLOOD VESSELS OF THE HEART

THE HEART The Vena Cava carry deoxygenated blood from all over the body to the right atrium. The Superior Vena Cava collect deoxygenated from the upper parts of the body. The Inferior Vena Cava collect the blood from the lower parts of the body.

The blood then flows into the right ventricle. It is then pumped into pulmonary artery.

Pulmonary Circulation The Pulmonary Artery carries deoxygenated blood from the right ventricle to the lungs. It divides in two, one to each lung. This blood is oxygenated in the lungs. The Pulmonary Veins carry oxygenated blood from the lungs to the left atrium of the heart. There are four pulmonary veins, two from each lung.

Systemic or General Circulation The left ventricle contracts and pumps blood out of the heart through the aorta. The aorta is the major artery of the body. It carries blood all over the body. It collects carbon dioxide. The deoxygenated blood travels back to the right atria through the vena cava.

Blood Flow Through the Heart Pulmonary Artery Aorta Superior Vena Cava Pulmonary Veins BLUE = deoxygenated blood RED = oxygenated blood Inferior Vena Cava

Blood Flow Through the Heart

Blood Flow Through the Heart

BLOOD VESSELS The tubes that carry blood are known as blood vessels. There are three types: Arteries Veins Capillaries

BLOOD VESSELS Arteries carry blood away from the heart. Veins carry blood towards the heart. Capillaries connect arteries to veins.

THE DIFFERENCES BETWEEN ARTERIES AND VEINS The blood in the arteries is under much higher pressure than in veins. This means that the wall of an artery is much thicker than that of a vein. This also means that the passage through an artery is much narrower than in a vein.

THE DIFFERENCES BETWEEN ARTERIES AND VEINS Arteries do not have valves because the blood is under high pressure. To prevent low pressure blood flowing backwards, veins have valves.

THE DIFFERENCES BETWEEN ARTERIES AND VEINS The blood in arteries is oxygenated except for the pulmonary artery. The blood in veins is deoxygenated except for the pulmonary vein.

Structure of Arteries They are thick-walled tubes. They all have the same basic construction: A fibrous outer covering A middle layer of muscle and elastic tissue An endothelial layer (a single layer of flattened cells)

Structure of Capillaries The capillaries are the smallest blood vessels. Their walls are one cell thick and porous, thus allowing the passage og gases and nutrients.

Structure of Veins They have three-layered walls similar to that of arteries. Their walls are much thinner and the lumen is larger. They have a fibrous outer coating A middle layer of muscle and elastic tissue An endothelial layer They have valves to prevent the back flow of blood.

THE HEARTBEAT When the heart pumps, a pulse of blood is sent down the arteries. This pulse can be felt in several places, e.g. the wrist, the temples and the neck.

What is Pulse The rate at which your heart pumps blood through your circulatory system. When blood is pumped from the left ventricle into the aorta, the aorta swells. The elastic wall of the aorta contacts thus forcing the blood to move on.

This sets up a wave of swelling and contracting which continues along all the elastic tissues. It can be felt wherever an artery passes close to the surface of the skin and over a bone. Most adults heartbeat is 72 – 80 beats per minute. Babies have a beat of 130 times a minute.

Anaemia Is a reduction in the bloods ability to carry oxygen. It may be caused by : Loss of blood, Lack of iron in the diet, A failure of the bone marrow to produce the normal level of red blood cells.

THE HEARTBEAT The normal human heartbeat is seventy beats per minute. The normal human adult breathing rate is 16-17 breaths per minute.

THE HEARTBEAT If more oxygen is needed by the muscles and the brain the rate of the heartbeat increases. Extra blood is pumped to these organs and so they get extra oxygen. Carbon dioxide is also removed faster.

FACTORS THAT INCREASE THE RATE OF THE HEARTBEAT INCLUDE: EXERCISE A FRIGHT SMOKING EXCITEMENT

FACTORS THAT DECREASE THE RATE OF THE HEARTBEAT INCLUDE: REST AND SLEEP