3.2 - transport in animals

• Multicellular organisms require transport systems because they have

  large size

  high metabolic rates

  high demand for oxygen

  so a specialised system ensures a strong supply to all respiring tissues
• What are the different types of circulatory system?

  open

  closed

  single

  double
• An open circulatory system is when the blood can diffuse out of vessels

  eg, insects
• A closed circulatory system is when blood is confined to vessels

  eg, fish or mammals
• A single circulatory system is when the blood passes through the heart once per full circuit of the body
• A double circulatory system is when the blood passes through the heart twice per full circuit of the body
• Arteries have:

  thick muscular walls - to handle high pressure without tearing

  elastic tissue - allows stretch and recoil

  narrow lumen - to maintain pressure
• Veins have:

  thin walls - due to lower pressure

  valves - to prevent back flow of blood

  less muscular and elastic tissue - dont need to control blood flow / pressure

  wide lumen - to increase volume of blood
• Capillaries are:

  very narrow - so red blood cells can lie flat against the wall

  one cell thick walls - short diffusion pathway

  numerous and highly branched - large surface area
• Arterioles and Venules branch off arteries and veins to feed blood into capillaries

  smaller than arteries and veins so change in pressure is gradual as blood passes through increasingly smaller vessels
• Tissue fluid is a watery substance containing glucose, amino acids, oxygen and other nutrients.

  It supplies these to cells while also removing any waste materials
• hydrostatic pressure and Oncotic pressure influence formation of tissue fluid.

  • Hydrostatic pressure = higher at arterial end, lower at venous end
  • oncotic pressure = changing water potential of the capillaries as water moves out, induced by proteins in the plasma
• Tissue fluid is formed as blood is pumped through increasingly smaller vessels. The hydrostatic pressure is greater than Oncotic pressure so the fluid moves out of the capillaries. It then exchanges substances with the cells
• Tissue fluid contains:

  • Water
  • dissolved solutes
  • few proteins
  • few white blood cells
• Blood contains:

  • Red blood cells
  • white blood cells
  • platelets
  • proteins
  • water
  • dissolved solutes
• Lymph contains:

  • white blood cells
  • water
  • dissolved solutes
  • few proteins (only antibodies)
• After tissue fluid has bathed cells it becomes lymph. And therefore lymph contains less oxygen and nutrients and more waste products.
• Systole is when the heart contracts
• Diastole is when the heart relaxes
• Diagram of the heart including chambers valves and vessels

  
• During cardiac diastole, the heart is relaxed.

  blood enters the atria, increasing the pressure and pushing open the atrioventricular valves. This allows blood to flow into the ventricles. Pressure in the heart is lower than in arteries so semilunar valves remain closed
• During atrial systole the atria contract, pushing any remaining blood into the ventricles
• During ventricular systole, the ventricles contract. the pressure increases in ventricles, closing the atrioventricular valves to prevent backflow, and opening the semilunar valves so blood flows into the arteries
• Atrioventricular valves are between the atria and the ventricles
• The specialised muscle found in the walls of the heart chambers is cardiac muscle
• Semilunar valves are found between ventricles and arteries
• The right side of the heart pumps deoxygenated blood to the lungs
• The left side of the heart pumps oxygenated blood to the rest of the body
• Coronary arteries lie over the surface of the heart to provide a constant supply of oxygenated blood
• If coronary arteries become congested it can lead to angina or heart attack
• The two atrioventricular valves are:

  right side - tricuspid valve

  left side - bicuspid valve
• pathway of deoxygenated blood in the heart

  enters vena cava , into the right atrium , through atrioventricular valve into right ventricle , through semilunar valve into pulmonary artery , travels to lungs to be oxygenated
• Pathway of oxygenated blood in the heart

  enters pulmonary vein , into the left atrium , through atrioventricular valve into left ventricle , through semilunar valve into aorta which pumps blood to the rest of the body
• Cardiac cycle is

  Diastole

  atrial systole

  ventricular systole
• Two parts of circulation in a double circulatory system are pulmonary circulation (heart to lungs) and systemic circulation (heart to body)
• Advantage of double circulatory system is being able to deliver blood t the lungs at lower pressure
• Disadvantage of single circulatory system is organism can only grow to a certain size.

  Blood has to flow at a much slower rate due to its lower pressure
• The muscle in arterioles are involved in vasoconstriction and vasodilation to control blood flow
• Tendons in the heart hold valves in place and prevent them from inverting on themselves
• cardiac output = heart rate x stroke volume