heart & blood vessels

• what is the heart?

  organ that pumps blood around the body in a double circulatory system
• where does the right ventricle pump blood to?

  pumps deoxygenated blood to the lungs where gas exchange takes place
• where does the left ventricle pump blood to?

  pumps oxygenated blood around the rest of the body
• describe how the heart functions

  • blood flows into the two atria from the vena cava & the pulmonary vein
  • the atria contract, pushing the blood into the ventricles
  • the ventricles contract, forcing the blood into the pulmonary artery & aorta, & out of the heart
  • blood flows to the organs through arteries & returns through veins

  
• why is the double circulatory system important?

  makes circulatory system more efficient - oxygenated blood can be pumped around the body at a higher pressure by the left ventricle
• why is the wall of the left ventricle thicker?

  has to pump blood around the body at a higher pressure
• what is the purpose of valves in the heart?

  prevent backflow of blood
• what is the purpose of coronary arteries?

  supply the heart muscle w oxygenated blood
• how is heart rate controlled?

  a group of cells in the right atrium that act as pacemaker
• what can be used to correct irregular pacemaker?

  artificial pacemakers which are electrical devices
• 3 types of blood vessel in the body:

  • veins
  • capillaries
  • arteries
• what is the function of arteries?

  carry blood away from the heart
• how are arteries adapted for their function?

  • thick muscle layer - strong to resist high pressure
  • thick elastic layer- allow arteries to stretch & recoil in order to withstand high pressure
• what is the function of the veins?

  carry blood towards the heart
• how are veins adapted for their function?

  • wide lumen- enables low pressure
  • valves- prevent backflow of blood
  • thinner walls
• what is the function of capillaries?

  enable transfer of substances between the blood & tissues
• how are capillaries adapted for their function?

  • walls one cell thick - short diffusion pathway
  • permeable walls- substances can diffuse accross
  • narrow lumen- blood moves slowly, more time for diffusion
• how does gas exchange occur at the alveoli?

  • oxygen diffuses from the alveoli into the capillary bloodstream down its concentration gradient
  • carbon dioxide diffuses from the capillary into the alveoli down its concentration gradient