Circulatory system

• Phagocyte structure 


  . They contain a nucleus which is required for producing enzymes for digesting pathogens

  . Can change shape to engulf materials

  . Flexible membrane - can fit through pores in capillary walls
• Red blood cells structure

  . Disc shaped, which provides a larger surface area for the diffusion of gases.

  . Small and flexible can fit through capillaries

  . No nucleus more space for hemoglobin molecules - increases oxygen carrying capacity of cell
• Function of red blood cells

  Carries oxygen
• Function of white blood cells

  Phagocytes engulf and destroy pathogens
• Function of plasma


  Transports hormones and proteins
• Function of platelets


  Role in blood cotting
• Heart


  Is made of muscle which contracts to pump blood around the body
• Blood flow


  Pulmonary vein, left atrium, left ventricle, aorta, body, vena cava, right atrium, right ventricle, pulmonary artery, lungs
• Structure of heart


  The left and right atria and ventricles, tricuspid and bicuspid valves, semi-lunar valves, pulmonary artery, pulmonary vein, aorta and vena cava. Need to label them too
• Bicuspid valve


  Stops blood back flowing backwards from ventricles into atria
• Tricuspid valve


  Stops blood back flowing backwards from ventricles into atria
• Semi lunar valve


  Makes sure blood is not drawn backwards into ventricles
• Pulmonary circuit


  . Involves right side of the heart

  . Deoxygenated blood transported to lungs

  . Gaseous exchange occurs between alveoli and capillaries

  . Oxygenated blood returns to left side of the heart
• Systemic circuit


  . Involves left side of the heart

  . Oxygenated blood pumped to tissues and organs around the body

  . Exchange of materials occurs at tissues

  . Deoxygenated blood returns to right side of the heart
• Coronary artery


  Supplies heart muscle with oxygen and nutrients
• Function of arteries


  Carries blood away from the heart under high pressure
• Structure of arteries


  . Narrow lumen maintains high pressure

  . Thick wall to withstand high pressure

  . Smooth inner lining to reduce friction
• Function of veins


  Carries blood towards the heart under low pressure
• Structure of veins


  . Large lumen

  . Thin layer of smooth muscle and elastic fibres

  . Valves prevent backflow of blood
• Function of capillaries


  Enables exchange of materials at tissues
• Structure of capillaries


  . Forms large network - greater surface area for diffusion

  . Walls one cell thick - short diffusion distance

  . Narrow lumen - Decreases diffusion distance
• What happens in organs

  In the organs, blood flows through very small blood vessels called capillaries; substances needed by cells diffuse out of the blood to the tissues, and substances produced by the cells diffuse into the blood, through the walls of the capillaries; the thin walls of the capillaries are an advantage for diffusion; capillaries form extensive networks so that every cell is near to a capillary carrying blood
• Risk factors for cardiovascular disease and effects

  . Lack of exercise - improves efficiency of heart and reduced obesity

  . Poor diet - High in fat and salt

  .Obesity - Fat builds up around the heart muscle, heart must work harder to pump blood around the body
• How does semi lunar valve ensure one flow of blood through heart

  Valve opens when heart contracts and closes when heart relaxes to prevent backflow of blood
• Why are left ventricles walls thicker than right ventricles

  Left ventricle pumps to body whilst right ventricle pumps blood to lungs so distance isn't as far
• How does blood from right atrium travel to left atrium

  Muscle of right ventricle contracts and pumps blood through valves of pulmonary artery into the lungs. Blood then leaves lungs passing into the pulmonary vein re entering the heart in left atrium
• Compare the structure of arteries and a vein

  . Arteries have thick walls to withstand the high pressure

  . Veins have thin muscles because blood is moving at a low pressure.

  . Arteries have a narrow lumen to carry oxygenated blood away from heart to tissues

  . Veins have a large lumen for ease blood flow

  . Arteries carries blood away from heart and veins take blood to heart and veins have valves which prevent backflow of blood.
• Explain why lack of exercise can result in obesity

  Calories are not being used so they are stored as fat