Humans

• The blood contains red blood cells, white blood cells, platelets and plasma
• Plasma carries carbon dioxide, digested food, urea, hormones and heat energy around the body, and it makes up 55% of the blood
• Red blood cells are bi-concave shaped, lack a nucleus and contain haemoglobin which binds to oxygen
• The immune system uses white blood cells to deal with disease, phagocytes to ingest and digest the pathogen, and lymphocytes releasing antibodies specific to the pathogen
• The right hand side of the heart pumps deoxygenated blood to the lungs
• The left hand side of the heart pumps oxygenated blood around the body
• The atria receive blood from the veins, vena cava on the right, the pulmonary vein on the left
• The ventricles pump blood to either the lungs or the rest of the body
• The septum separates the different sides of the heart
• The tricuspid valve is between the right atrium and ventricle
• The bicuspid valve is between the left atrium and ventricle
• The semi-lunar valves prevent backflow of blood into the heart, and are found in the aorta and pulmonary artery
• The heart rate increases during exercise, because muscles respire more, needing more oxygen to maintain aerobic respiration, so the heart pumps faster to get oxygen to the respiring muscles. High levels of blood CO2 are detected by receptors in the aorta and carotid artery, which send signals to the brain, then to the heart
• When an organism is threatened, the adrenal glands release adrenaline, which binds to receptors in the heart, causing cardiac muscles to contract more frequently, raising the heart rate and increases oxygen supplies to tissues
• Coronary heart disease is caused by cholesterol building up in the coronary arteries, meaning they become narrow, and there is a lack of bloodflow to the heart, leading to heart attacks
• Coronary heart disease has many factors, such as having a diet high in saturated fat, smoking, and inactivity
• Arteries have strong elastic walls, to cope with the high pressure of blood inside, and also have a small lumen relative to the walls
• Veins have bigger lumens than arteries, to help bloodflow at a lower pressure. They also have valves to keep the blood flowing in the right direction
• Capillaries have walls only one cell thick, have a very small lumen, and carry blood close to every cell in the body to exchange substances via diffusion through their permeable walls