circulatory system and oxygen

specialised cardiac muscle cells

• long protein filaments 
• can slide past each other
• shortens the cell to bring about contraction 
• contraction pumps blood

arteries:

• heart pumps blood to lungs in pulmonary artery so oxygen can diffuse into blood from air in alveoli
• muscles pump blood to the body via the aorta
• carry oxygenated blood to tissues

veins:

• blood returns to heart via pulmonary vein
• valves to prevent backflow of blood

capillaries:

• large surface area to maximise exchange
• thin walls allow easy diffusion

waste products removed (e.g. CO2) diffuse from cells into blood plasma

red blood cells contain haemoglobin to bind oxygen

no nucleus, so there is more space available to carry oxygen

double circulatory system

• higher blood pressure
• greater flow of blood to the tissues

cardiac output can vary

• according to demand
• is affected by adrenaline
• can divert blood to large muscles - preparation for 'fight or flight'