2. Multicellular organisms need transport systems to deal with surface area to volume ratio issue. Animal transport and exchange systems In mammals, nutrients, oxygen and carbon dioxide are transported in the blood. Pathway of blood through heart, lungs and body. Heart structure to include right and left atria and ventricles. Blood vessels to include: aorta, vena cava, pulmonary arteries and veins, and coronary arteries. Arteries have thick, muscular walls, a narrow central channel and carry blood under high pressure. Veins carry blood under low pressure; have thinner walls and a wide channel. Veins contain valves to prevent backflow of blood. Capillaries form networks at organs and tissues, and are thin walled and have a large surface area, allowing exchange of materials. Red blood cells contain haemoglobin and are specialised to carry oxygen Heart – syllabus content

3. Structure of the heart Right atrium Chambers of the heart Right ventricle Left atrium Left ventricle Heart structure to include right and left atria and ventricles. Note: The left ventricle has a thicker wall (more muscle in its wall) than the right ventricle because it pumps blood further

4. Blood vessels entering and leaving the heart Vena cava Blood coming from the body Pulmonary artery Blood to the lungs Pulmonary vein Blood from the lungs Aorta Blood to the body X X Xx Position of heart valves Blood vessels to include: aorta, vena cava, pulmonary arteries and veins, and coronary arteries.

5. The heart tissue receives blood from the coronary arteries Right coronary artery Left coronary artery Blood supply to the heart itself

6. Arteries have thick, muscular walls, a narrow central channel and carry blood under high pressure. Veins carry blood under low pressure; have thinner walls and a wide channel. Veins contain valves to prevent backflow of blood. ArteriesVeins Take blood away from the heart Take blood back to the heart Have thick muscular walls and a narrow lumen - blood is under high pressure Have thin walls and a wide lumen - blood is at low pressure Have valves to prevent backflow of blood No valves Artery structure Thick layer containing smooth muscle Narrow channel Vein structure Thin layer containing smooth muscle Wide channel

7. Capillaries Capillaries are very small, thin walled vessels that are found close to all body cells Substances are exchanged between the blood and cells through the capillary walls Capillaries form networks at organs and tissues, and are thin walled and have a large surface area, allowing exchange of materials.

8. Capillary beds Body cells are found close to capillaries in capillary beds Substances like glucose and oxygen pass by diffusion from the blood in the capillaries to the liquid around the cells then into the cells. Carbon dioxide diffuses in the other direction capillary Tissue fluid Body cells Glucose and oxygen Carbon dioxide Capillaries have a large surface area and thin walls to allow efficient exchange of substances

9. Oxygen is transported in red blood cells Red blood cells contain a substance called haemoglobin. When the oxygen concentration is high (in the lung capillaries), haemoglobin joins with oxygen to make oxyhaemoglobin Oxygen is carried in the blood joined to haemoglobin When the oxygen concentration is low (in the body capillaries) oxyhaemoglobin breaks down again to release the oxygen for the body cells. in lung capillaries in body capillaries Haemoglobin + oxygen oxyhaemoglobin Red blood cells contain haemoglobin and are specialised to carry oxygen