BLOOD CIRCULATORY SYSTEM

Cardiovascular System Every cell in the body needs oxygen to survive and there is only one way they can get it – through the blood. Blood has three main functions;- Transportation Regulation Protection (Tommy Prays Regularly)

Transportation Blood transports: Oxygen from the lings to the cells Carbon dioxide from the cells to the lungs Nutrients from the gastrointestinal tract to the cells Heat and waste away from cells Hormones from glands to cells

Regulation Blood regulates: The PH of the body The temperature of the body The water content of cells

Protection Blood protects the cells against foreign microbes and toxins and also has the ability to clot and so protect the body against excessive blood loss.

THE BLOOD Blood is composed of 55% straw-coloured fluid called plasma and 45% is made up of cells Three main types of blood cells: Erythrocytes Red blood cells Leucocytes White blood cells Thrombocytes Platelets

RED BLOOD CELLS Most numerous of all the blood cells. No nucleus and the cytoplasm is filled with haemoglobin which carries oxygen. Bi-concave shape Their membranes allow for the exchange of oxygen. Produced in the bone marrow.

WHITE BLOOD CELLS Leucocytes Primarily for protection of the body against foreign microbes. They live between a few hours to a few days and are pale whitish in colour. Can be categorised into granulocytes and agranulocytes.

Granulocytes Neutrophils – engulf and digest foreign particles through phagocytosis. Eosinophils – destroy certain parasitic worms and combat the effects of some inflammatory complexes. Basophils – contain histamine which causes dilation of blood vessels. They release histamine at sites of inflammation

Agranulocytes Lymphocytes – play an important role in immune response and are present in lymphatic tissue such as the lymph nodes. Monocytes – some circulate in blood and are phagocytic others migrate to the tissues to become macrophages which clean up infection.

Thrombocytes Thrombocytes function in heamostasis, which is the process by which bleeding stops. Thrombocytes form a platelet plug and release chemicals that promote blood clotting.

Clotting Platelets will clot a damaged area where blood loss has occurred. Clotting prevents excess blood loss and protects against microbe entry.

BLOOD VESSELS Blood flows around the body by the pumping action of the heart and is carried in vessels known as :- Arteries Veins Capillaries

ARTERIES Carry blood under pressure away from the heart. Thick muscular walls to withstand pressure. No valves Carry oxygenated blood, except for the pulmonary artery. Lie deeper than veins

VEINS Carry blood back to the heart under low pressure. The walls are less thick and elastic. Valves prevent backflow. Carry deoxygenated blood except for the pulmonary vein.

CAPILLARIES Smallest vessels. They join the arterioles and the venules. Only one cell thick to allow for the transfer of substances between the cells and the capillaries. Have no valves

CAPILLARY EXCHANGE The exchange of substances between tissue cells in the body and the blood in the capillaries. Oxygen, nutrients, vitamins and minerals pass into the tissue fluid to nourish the cells. Carbon dioxide and waste products pass out of the cell and back into the blood to be excreted.

THE HEART Made up of cardiac muscle tissue. Lies in the centre of the thorax under the sternum Made up of three layers Pericardium, outer layer that encloses the heart Myocardium, middle layer of strong muscle Endocardium, inner layer which lines the heart cavities

FUNCTION OF THE HEART Acts as a pump. To maintain a constant circulation of blood in the body. The heart rate will speed up or slow depending on the volume of blood required by the body.

MAIN BLOOD VESSELS OF THE HEART MAIN ARTERIES AORTA Takes oxygenated blood to the body PULMONARY ARTERY Takes deoxygenated blood to the lungs MAIN VEINS SUPERIOR AND INFERIOR VENA CAVI Brings deoxygenated blood from the body back to the heart. PULMONARY VEINS Brings oxygenated blood from the lungs to the heart

BLOOD FLOW THROUGH THE HEART Deoxygenated blood flows through the right side of the heart and is pumped to the lungs to pick up oxygen. It then travels back to the left side of the heart where it is pumped around the body.

CONTRACTION OF THE HEART The atria contract together to force the blood into the ventricles. The atria then relax and the ventricles contract to push the blood out of the heart and around the body

BLOOD CIRCULATION There are two main divisions to the blood circulation Pulmonary circulation Systemic or general circulation

PULMONARY CIRCULATION The circulation of the blood to the lungs, where carbon dioxide is removed and oxygen obtained before it returns to the heart.

SYSTEMIC CIRCULATION The circulation of oxygenated blood around the body and the return of deoxygenated blood to the heart. Blood leaves the heart via the aorta which divides into branches to supply the different areas of the body

BRANCHES OF THE AORTA The ascending arch supplies the head, neck and top of arms. Descending thoracic supplies the organs of the thorax. Descending abdominal supplies the legs, renal, digestive and reproductive systems.

ARTERIES TO THE HEAD Facial artery Occipital artery Carotid artery

VEINS FROM THE HEAD External Jugular Internal Jugular

BLOOD SHUNTING The system of diverting blood from some areas of the body to other areas where it is in need. For example, blood is diverted to the muscles during exercise where it is required and away from the digestive system where it is not vital.

BLOOD PRESSURE The force with which blood is pumped through the vessels. The maximum (systolic) pressure is when the blood has just been pushed into the arteries. The minimum (diastolic) pressure is when the heart relaxes and blood flows into the heart from the veins.

FACTORS AFFECTING BP Anything that makes the heart beat faster will raise the blood pressure. Excitement Anger Stress Fright Pain Exercise Smoking and drugs

THE PULSE The pulse is the wave of blood as it passes through the arteries. It can be felt at positions on the body where the arteries pass close to the surface.

The Cardiac Cycle Systole – contraction Diastole - relaxation The cardiac cycle lasts approximately 0.8 seconds and is involved with the contraction and relaxation of both atria and ventricles. Systole – contraction Diastole - relaxation

ECG trace

Cardiac diastole This occurs at the end of the heartbeat and all four chambers relax.

Atrial systol The SA node stimulate the contraction of the atria. They contract simultaneously and empty all their contents into the ventricles.

Ventricular systole Ventricular contraction is then triggered by the AV node and as the ventricles contract blood is pushed up against the AV valves, forcing them shut.

Cardiac diastole After ventricular contraction both the atria and ventricles are relaxed, therefore starting another cycle.

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