 Clare Hargreaves-Norris Blood ACCESS HE Human Biology.

 Clare Hargreaves-Norris Introduction The circulatory system is comprised of: Blood, this fluid transports vital substances to all areas of the body. Blood is transported in vessels known as arteries, veins and capillaries. The heart acts as a pump to move the blood around the body.

 Clare Hargreaves-Norris Main Functions of Blood. There are three main functions of blood. – Transportation. – Defence. – Regulatio.

 Clare Hargreaves-Norris 1. Transportation Erythrocytes, (red blood cells), carry oxygen to the cells of the body. Carbon dioxide is carried back to the lungs. Nutrients such as glucose, vitamins and minerals are transported around the body. Hormones are secreted into the blood and attach to the plasma so that they can be transported around the body to their target organs. All waste materials such as urea are carried in the blood to be removed and excreted.

 Clare Hargreaves-Norris 2. Defence There are five types of leucocytes, (white blood cells). All leucocytes are responsible fighting infection, (protecting the body from disease). Some leucocytes work as phagocytes, (they engulf and destroy microorganisms). Some leucocytes, (lymphocytes), produce antibodies, which give the body future resistance to re-infection. Coagulation. Platelets start the clotting process to prevent excessive blood loss and to stop infection from gaining entry into the body.

 Clare Hargreaves-Norris 3. Regulation Blood regulates body heat by absorbing it from the liver and muscles as it passes by, and then transports it around the body.

 Clare Hargreaves-Norris Composition of blood Blood is made from Plasma (55%) a straw- coloured fluid Erythrocytes (red blood cells) Leucocytes (white blood cells) Platelets (Thrombocytes)

 Clare Hargreaves-Norris StructureFunction Plasma 90% water. 8% plasma proteins. 2% hormones, enzymes, nutrients, inorganic ions (electrolytes) and waste. Renews the cellular fluid. Maintenance of pH of the blood at 7.4. Makes the blood viscous. Provision of energy to the cells. Produces chemical reactions. Protection against infection.

 Clare Hargreaves-Norris StructureFunction Erythrocytes (red blood cells) Minute biconcave discs. Obtain their red colour from haemoglobin that combines with oxygen to form oxyhaemoglobin. Made in the red bone marrow. Take approximately 7 days to form. They function for approximately 4 months. They are then destroyed by the liver or spleen. Red blood cells carry oxygen around the body to the cells. Carbon dioxide is taken away from the cells.

 Clare Hargreaves-Norris StructureFunction Leucocytes (white blood cells) Colourless cells. Contain a nucleus. Larger than red blood cells. Less white cells than red. Ratio approximately 1 to every 600 red cells. 2 different types: 1. Granulocytes, (75%), -Neutrophils, (54%), phagocytosis. - Eosinophils, (1%), allergic reactions, defence against worms. -Basophils, (!%), inflammatory response. 1. Agranulocytes. -Lymphocytes, (23%), produce antibodies to kill foreign proteins. -Monocytes, (2%), phagocytosis.

 Clare Hargreaves-Norris StructureFunction Platelets (Thrombocytes). Platelets are formed in the red bone marrow. Tiny fragments. Even smaller than red blood cells. Start the blood clotting process by producing a substance called thrombokinase. This sets off a chain of reactions. This results in the laying of fibres, which cover the wound. Prevention of blood loss. Prevention against invasion of infective microbes.

 Clare Hargreaves-Norris Blood clotting Platelets produce a substance called thrombokinase. This sets off a chain of reactions resulting in the laying of fibres which cover the wound. This prevents blood loss and invasion of foreign materials. When the blood clots it forms a scab. This is a natural protective seal to the area.

 Clare Hargreaves-Norris Factors affecting the blood clotting process It is important that you are aware that certain factors can affect the blood clotting process. The health and efficiency of the blood supply can be affected by: Smoking Alcohol Poor nutrition intake Anti-coagulant drugs such as warfarin and aspirin.