circulatory system

• what is the function of the circulatory system?

  Multicellular organisms have a smaller surface area to volume ratio, so they need a specialised mass transport system to carry raw materials from organs to cells.
• What is the circulatory system made up of?

  Heart and blood vessels
• Where does the heart pump blood through?

  Bloods vessels - arteries, arterioles, veins and capillaries
• What are the different blood vessels called?

  1. Pulmonary artery
  2. Pulmonary vein
  3. Aorta
  4. Vena cava
  5. Renal artery
  6. Renal vein
• Where do the pulmonary arteries carry blood from and to?

  Carries blood from the heart and into the lungs
• Where does the pulmonary vein carry blood from and to?

  Carries blood from the lungs and to the heart
• Where does the aorta carry blood from and to?

  Carries blood from the heart and to the body
• Where does the vena carry carry blood from and to?

  Carries blood from the body and to the heart
• Where does the renal artery carry blood from and to?

  Carries blood from the body and to the kidneys
• Where does the renal vein carry blood from and to?

  Carries blood from the kidneys to the vena cava
• What does blood transport around the body?

  1. Respiratory gases
  2. Products of digestion
  3. Metabolic wastes
  4. Hormones
• What are the two circuits in the body?

  1. Takes blood from the heart to the lungs, then back to the heart
  2. Takes blood to the rest of the body, therefore blood has to go through the heart twice to complete one full circuit of the body
• What is the blood supply for the heart?

  The left and right coronary arteries
• What do arteries do?

  Carry blood from the heart to the rest of the body
• What is the structure of the arteries?

  Their walls are thick and muscular, they have elastic tissue.
• How does elastic tissue and the endothelium help an artery?

  Elastic tissue - stretches and recoils as the heart beats and maintains a high pressure

  Endothelium - artery can stretch to help maintain high pressure
• What do arteries carry?

  Pulmonary artery - takes deoxygenated blood to the lungs

  All other arteries - carry oxygenated blood
• What are arterioles?

  Arteries which have divided into smaller vessels and formed a network throughout the body
• What do arterioles do?

  Muscles inside the arterioles direct blood into different areas of demand in the body by contracting to restrict blood flow and relaxing to allow full blood flow
• What is the function of the vein?

  They take blood back to the heart under low pressure
• What is the structure of a vein?

  They have a wider lumen than an artery, and have very little elastic or muscular tissue and they contain valves
• What do the valves in veins do?

  Stop the backflow of blood
• What do veins carry?

  All other veins - Deoxygenated blood because oxygen has been used up by the cells

  Pulmonary vein - carries oxygenated blood from the lungs and to the heart
• What are capillaries?

  Arterioles which have branches into smaller blood vessels
• Where are capillaries found and why?

  Near cells in exchange tissues to allow a short diffusion pathway
• What is the structure of a capillary?

  Walls are one cell thick, shortening the diffusion pathway

  Large number of capillaries to increase the surface area for exchange

  There are networks of capillaries called capillary beds
• How are capillaries adapted for efficient diffusion?

  Substances are exchanged between cells and capillaries
• What is tissue fluid?

  Fluid that surrounds cells in tissues
• What is tissue fluid made from?

  Small molecules that leave the blood plasma (e.g., oxygen, water.)
• What do substances move out of the capillaries and into the tissue fluid by?

  Pressure filtration
• What is pressure filtration?

  1. Start of the capillary bed, hydrostatic pressure inside capillaries is greater than hydrostatic pressure in the tissue fluid
  2. Difference in pressure means an overall outward pressure forces fluid out of the capillaries and into the space around the cells, forming tissue fluid
  3. As fluid leaves, hydrostatic pressure reduces in the capillaries
• What happens because of fluid loss in the capillaries?

  The water potential at the end of the capillary bed is lower than the water potential in the tissue fluid so some water re-enters the capillaries from tissue fluid by osmosis.
• Where is excess fluid drained?

  Lymphatic system - transports excess fluid from tissues and passes it back into the circulatory system
• What is the lymphatic system?

  Network of tubes that act like a drain