Transport in animals

• Why do large organisms need a transport system?

  • Large organisms have a decreased rate of diffusion due to the decrease in surface area to volume ratio and longer diffusion path
  • They also have a higher metabolic rate – due to muscle contraction, organ systems demand greater need for specialised transport systems with a pump e.g. heart
• Why is the system a double circulatory system?

  Because blood passes through the heart twice in one complete circuit of the body
• Why is it a closed circulatory system?

  As blood is enclosed inside blood vessels at all time
• What is the role of coronary arteries?

  They supply the heart with essential nutrients and oxygen. These cells have a high concentration of mitochondria for aerobic respiration to generate ATP. The aorta supplies the coronary arteries with blood
• Function of right atrium:

  Receives deoxygenated blood from the body
• Function of superior vena cava:


  Brings blood from the upper body and head to the

  right atrium
• Function of inferior vena cava:

  Brings deoxygenated blood from the lower part of

  the body to the right atrium
• Function of right ventricle:

  Pumps deoxygenated blood to the lungs
• Function of right atrio-ventricular valve:

  Allows blood to flow from right atrium to right

  ventricle but stops backflow.
• Function of pulmonary arteries:

  Carry deoxygenated blood from right ventricle to

  the lungs
• Function of left atrium:

  Receives oxygenated blood from the lungs
• Function of pulmonary veins:

  Carry oxygenated blood from the lungs to the

  left atrium
• Function of left ventricle:

  Pumps oxygenated blood to the body via the

  aorta
• Function of left atrio-ventricular valve:

  Allows blood to flow from left atrium to left

  ventricle and prevents backflow.
• Function of aorta:

  Carries oxygenated blood to the body from the

  left ventricle
• Function of septum:

  Tissue which divides the two sides of the heart
• Function of tendinous cords:

  Prevent the atrio-ventricular valves

  from turning inside out when the ventricles

  contract.
• Function of semi-lunar valves:

  Prevent backflow in the aorta and pulmonary

  artery
• How do valves work?

  When the atria contracts, this increases the pressure in the atria, causing the AV valves to open and blood flows into the ventricle. When the ventricle has a higher pressure than the atria, the AV valves close. This ensures blood only flows in one direction
• What are the stages of the cardiac cycle?

  Diastole

  Atrial systole

  Ventricular systole

  Diastole again
• What happens during diastole?

  ● Both atria and ventricles relax.

  ● Blood enters the atria at a low pressure from the veins and the AV valves are currently open, therefore some of the blood also flows into the relaxed ventricles
• What happens during atrial systole?

  Both atria contract. The pressure in the atria increases and exceeds the

  pressure in the ventricles. The AV valves are forced open and blood flows into the ventricles.
• What happens during ventricular systole?

  ● The pressure in the ventricles increases and exceeds the pressure in the atria. The AV valves are forced closed.

  ● The pressure in the ventricles also exceeds the pressure in the arteries.

  The Semi-lunar valves are forced open and blood flows into the arteries.

  ● Ventricle contraction is from the base of the heart upward meaning no blood is left in the ventricles at the end of the cardiac cycle.