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Why do organisms need a transport system? • In large organisms, the distance over which oxygen, carbon dioxide, nutrients and wastes have to move is too L-O-N-G for food absorption and gaseous exchange to occur efficiently Transport Systems in Humans Circulatory System Lymphatic System Circulatory System BLOOD Human Circulatory System BLOOD VESSELS HEART Blood • Blood is a LIQUID TISSUE consisting of blood cells which float in a liquid • Blood acts as a TRANSPORT MEDIUM to carry various substances in the forms of solution and suspension Blood • The various components in blood can be separated by a machine called a CENTRIFUGE • After centrifugation, blood is divided into two portions Blood Plasma (55% by volume) Blood Cells (45% by volume) (red colour) (straw colour) What is blood made up of? BLOOD CELLS 250 000/mm3 7 000/mm3 5 000 000/mm3 Blood Cells White Blood Cell Red Blood Cell Platelet Where are blood cells made? Red Blood Cells (Erythrocytes ) Red Blood Cells • RBC’s are formed in BONE MARROW • They have a short life-span: about 120 days only • Old RBC’s are destroyed in the liver and the spleen • Matured RBC’s in mammals do not possess a nucleus Red Blood Cells • They are shaped like biconcave discs in order to provide a large surface area for diffusion of gases • Their red colour comes from haemoglobin which is responsible for carrying oxygen from the lungs to all parts of the body Transport of Oxygen Transport of Oxygen Transport of Oxygen Transport of Oxygen Haemoglobin + Oxygen (Purplish Red) In Lungs In Tissues Oxyhaemoglobin (Bright Red) Transport of Carbon Dioxide • Most of the carbon dioxide is carried in the blood in the form of hydrogencarbonate ions (HCO3-). An enzyme inside the RBC helps to convert the CO2 into HCO3- and vice versa Investigation #1: To investigate the effects of oxygen and carbon dioxide on chicken’s blood Procedure White Blood Cells (Leukocytes) • • • • Irregularly-shaped Possess nucleus Kill pathogens Number of WBC’s in body can vary • Different WBC’s have different lifespans: ranging from 10 hours to over 1 year White Blood Cells 1) Phagocytes • They are made in the bone marrow • They have a lobed nucleus • They can move like an Amoeba out of blood capillaries to engulf germs and dead cells Phagocytes Bacteria Phagocyte White Blood Cells 2) Lymphocytes • They have a large nucleus • They are made in the bone marrow and then migrate to lymph nodes • Some lymphocytes produce antibodies; others kill invading cells directly • They also produce antitoxins to neutralize toxins produced by germs When the lymphocyte encounters a matching antigen, the antibody interlocks with the antigen and marks it for destruction Leukaemia • Leukaemia is a cancer of the tissues which produce blood • Large numbers of abnormal white cells are produced, which are unable to carry out their normal function of fighting infection • The abnormal cells also displace the normal production of red cells and platelets • Can be treated with chemotherapy, radiotherapy or bone marrow transplant Platelets (Thrombocytes) • Tiny fragments formed from specialized cells in the bone marrow • They have no nucleus • They have a short life span: less than 10 days • They are involved in the process of blood clotting Platelets After the clot is formed, bleeding is stopped. The clot hardens to form a scab and the wound gradually heals Blood Clotting RBC’s trapped in a network of fibrin threads Platelet plug Blood vessel constricts to slow down blood loss Blood Clotting A Comparison of RBC’s, WBC’s and Platelets Red blood cells Site of production Bone marrow White blood cells Platelets Bone marrow, Bone marrow lymph nodes Number Size Shape Structure Function 5 000 000/mm3 8m diameter Biconcave disc-shaped No nucleus Haemogloblin 7 000/mm3 250,000/mm3 Lym:8-10m Tiny cell Phag:12m fragments Irregular Irregular Nucleus No nucleus No haemoglobin No haemoglobin Transport of oxygen Body defence Blood clotting PLASMA Dissolved Substances (10%) Water (90%) Plasma – Dissolved Substances • • • • • • • • Plasma proteins – antibodies, fibrinogen Lipids Nutrients Glucose Amino acids Hormones – coordinate body activities Mineral salts Urea Wastes Carbon dioxide Investigation #2: Detecting the presence of glucose in a blood sample Procedure Functions of Blood Transportation of: 1. Oxygen – in the form of oxyhaemoglobin 2. Carbon dioxide – in the form of HCO33. Food – from ileum to all parts of body 4. Urea – from liver to kidneys 5. Hormones – from endocrine glands 6. Antibodies – to all parts of body 7. Heat – to keep uniform temperature Functions of Blood Defence against infection: 1. Phagocytes engulf germs 2. Lymphocytes produce antibodies to destroy germs or antitoxins to neutralize toxins 3. Blood clotting prevents excess blood loss and entrance of bacteria Blood Vessels • • • * * A system of tubes for distributing blood around the body: Artery – carry blood AWAY from the heart Vein – carry blood TOWARDS the heart Capillary – narrow vessel connecting arteries and veins Arteries branch into smaller vessels called arterioles Small vessels called venules join into veins 16 (kPa) Blood pressure Changes in blood pressure in different types of blood vessels 8 With pulse No pulse Arteries Capillaries Arterioles Venules Veins Arteries • Carry blood AWAY from the heart • Contain oxygenated blood (exception: pulmonary artery) • Thick walls of muscles • Elastic fibres allow arterial wall to withstand pressure • Lumen is small and appeared to be round • No valves • Need to withstand high pressure • The muscles around the artery can contract or relax to allow the vessel to constrict or dilate Arteries Veins • Carry blood TOWARDS the heart • Contain deoxygenated blood (exception: pulmonary vein) • Thinner walls compared to those of arteries • Walls are less elastic • and muscular • Lumen is larger and appeared flattened • Contain valves that are surrounded by skeletal muscles Pressure of blood is low Veins