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Why do we need a transport system? • We have a small surface area to volume ratio • Simple diffusion throughout the body surfaces is insufficient • Useful substances needs to transported through the body and unwanted substances needs to be eliminated What is the importance of the circulatory system? • It transports blood throughout our body – to all parts of our body • Needed substances by the body such as: oxygen, nutrients and hormones are sent to all cells in the body • Unwanted substances such as carbon dioxide and nitrogenous waste products are sent to be eliminated by the body. What does our transport system consist of? • A transporting medium – the blood • Tubes through which the medium can travel – blood vessels • A pump to push the medium through the tubes – the heart Objective: To describe the composition and components of blood BLOOD what’s in digested food red blood cells white blood cells oxygen waste (urea) platelets carbon dioxide plasma hormones The Blood red blood cell platelets white blood cell plasma Blood Components Composition of Blood • Blood is composed of three types of cells: red blood cells, white blood cells and platelets, floating in a liquid called plasma. • Plasma makes up 55% of the volume of the blood and the cells make up the other 45% Blood Cells Blood = 55% Plasma + 45% Blood Cells Red Blood Cells a biconcave disc that is round and flat without a nucleus contain haemoglobin, a molecule specially designed to hold oxygen and carry it to cells that need it. can change shape to an amazing extent, without breaking, as it squeezes single file through the capillaries. Red Blood Cells (Erythrocytes) • Formation – red bone marrow of the pelvis, scapula, ribs, sternum etc • Destroyed in the liver and spleen • Functions – transport oxygen as oxyhaemoglobin from lungs to tissues. Transport small amounts of carbon dioxide from tissues to lungs How do red blood cells transport oxygen? • In their cytoplasm is a red pigment called haemoglobin • Haemoglobin has a high affinity for oxygen • It forms an unstable compound called oxy-haemoglobin • In conditions of low oxygen concentration oxy-haemoglobin breaks down and releases the oxygen. Oxygen in Red Blood Cells Did you know? • There are about 5 ½ million red blood cells in a cubic millimetre of blood • A red blood cells lasts for about 4 months • About 200 billion red blood cells are formed and destroyed each day • About 1% of the total red blood cells are replaced each day. White Blood Cells (Leucocytes) there are many different types and all contain a big nucleus. the two main ones are the phagocytes and the lymphocytes. phagocytes ‘eat’ or engulf disease causing bacteria in the blood at sites of infection and the lymph nodes some lymphocytes fight disease by making antibodies to destroy antigens (foreign proteins) by dissolving them. other lymphocytes make antitoxins to break down poisons. Platelets (Thrombocytes) Platelets are formed in the bone marrow of long bones by disintegration of certain cells . Platelets produce tiny fibrinogen fibres to form a net. This net traps other blood cells to form a blood clot. Plasma It also contains useful things like; • carbon dioxide A strawcoloured liquid that carries the cells and the platelets which help blood clot. • glucose • amino acids • proteins • minerals • vitamins • hormones • waste materials like urea. Objective: To describe the structure and function of blood vessels BLOOD VESSELS blood from the heart gets around the body through blood vessels There are 3 types of blood vessels a. ARTERY b. VEIN c. CAPILLARY The ARTERY Arteries carry blood away from the heart. the elastic fibres allow the artery to stretch under pressure thick muscle and elastic fibres the thick muscle can contract to push the blood along. Arteries • Carries high pressure oxygenated blood away from the heart • Blood moves in pulses created by ventricle contractions • Most lie deep in the body where they are protected • Thick elastic walls composed of three layers to withstand high pressures of blood • Arteries divide into smaller vessels called arterioles Structure of an artery The CAPILLARY Capillaries link Arteries with Veins they exchange materials between the blood and other body cells. the wall of a capillary is only one cell thick (endothelial cells) The exchange of materials between the blood and the body can only occur through capillaries. The CAPILLARY A collection of capillaries is known as a capillary bed. arteriole body cell venule capillaries Did you know? • The capillary network is so dense that no living cell is far from a supply of food and oxygen • In the liver every cell is in direct contact with a capillary. Why do you think this is so? • Some capillaries are so narrow that the red blood cells are squeezed flat while passing through them. The VEIN Veins carry blood towards from the heart. veins have valves which act to stop the blood from going in the wrong direction. thin muscle and elastic fibres body muscles surround the veins so that when they contract to move the body, they also squeeze the veins and push the blood along the vessel. Structure of Veins Vein Valves Varicose Veins • This happens when the valves stop working properly • The blood is left in the veins instead of flowing back to the heart • This makes the vein swell and causes a varicose vein • Varicose veins show up on the legs ankle and knees because they are furthest from the heart SUMMARY copy and complete the following; away from the heart. The walls of an artery Arteries take blood ______ muscular walls and elastic fibres. Veins are made up of thick _________ towards the heart and also have valves. The carry blood ________ capillaries link arteries and veins, and have a one cell thick wall. _________ plasma the liquid part of the Blood is made up of four main things ______, oxygen White Blood cells to protect blood; Red Blood Cells to carry ______; platelets to help blood clot. the body from disease and _________