Mass transport in animals

• Multicellular organisms, e.g. fish and mammals, require a more specialised transport system as they can't get all the things thry require simply by diffusion.
• what 2 factors will cause the diffusion of materials in an organisms to become too slow to meet the needs of body cells?

  1. Smaller SA:V
  2. Increased activity of the organism
• Mammalian double circulatory system

  
• Artery - an organ that carries oxygenated blood away from the heart, under high pressure.

  A) Collagen for strength and strcuture

  B) Smooth muscle to contract and relax to change diameter

  C) Elastic tissue in walls to expand with each pulse

  D) Smooth endothelium cells to reduce friction

  E) Small lumen to withstand high pressures

  F) No valves as under high pressure

  
• Vein - a blood vessel that carries deoxygenated blood to the heart, under low pressure

  A) Collagen for strength and strcuture

  B) Less smooth muscle as no need to contract

  C) Endothelium cells smooth and reduces friction

  D) Large lumen as under lower pressure

  E) Little elastic tissue as low pressure

  F) Valves to prevent backflow

  
• Capillary - smallest blood vessel which supplies tissues with oxygen, nutrients and removes carbon dioxide.

  A) Single celled, flattened endothelium

  B) Small lumen to allow diffusion

  
• Structure of the heart

  A) Superior vena cava

  B) Inferior vena cava

  C) Right atrium

  D) Left ventricle

  E) Aortic valve

  F) Pulmonary valve

  G) Atrioventricular valve

  H) Atrioventricular valve

  I) Right ventricle

  J) Left atrium

  K) Aorta

  L) Pulmonary artery

  M) Pulmonary vein

  
• what are the 3 stages of the cardiac cycle?

  1. Atrial systole
  2. Ventricular systole
  3. Diastole

  
• What happens in atrial systole?

  1. Walls of atria contract - atria volume decreases and pressure increases
  2. Pressure in atria is higher than ventricles so AV valves open
  3. Blood is forced into ventricles

  
• What happens in ventricular systole?

  1. Walls of ventricle contract - ventricular volume decreases and pressure increases
  2. Pressure in ventricles is higher than atria so forces AV valves close
  3. Pressure in ventricles rises above aorta and pulmonary artery so forces semilunar valves open
  4. Blood is forced out of heart and into arteries.

  
• What happens in diastole?

  1. Ventricles and atria are both relaxed
  2. Pressure in ventricles is lower than the arteries so semilunar valves close
  3. Atria fills with blood via vena cava and pulmonary vein
  4. Pressure in atria rises above that in ventricles and AV valves open
  5. Blood flows passively into ventricles
  6. Cycle begins again!

  
• Definition of stroke volume - Volume of blood pumped out of the left ventricle in each heartbeat
• Definition of heart rate - Number of times the heart beats per minute.
• Cardiac output = stroke volume x heart rate
• Cardiac output = amount of blood pumped around the body.
• Pressure and volume changes in the heart and associated valve movements graph

  
• What is tissue fluid?

  Watery substance that bathes the cells within tissue containing materials that a cell needs or has to be removed from the cell
• What does the blood contain?

  1. Red blood cells
  2. White blood cells
  3. Platelets
  4. Oxygen
  5. Carbon dioxide
  6. Water
  7. Ions
  8. Urea
  9. Amino acids
  10. Glucose
  11. Fatty acids
• Hydrostatic pressure - pressure exerted by the fluid on the walls of the blood vessels.
• Osmotic pressure - The pressure that causes the diffusion of water through semi-permeable membranes
• Exchange of substances between cells and the blood occurs via the tissue fluid.
• Capillary bed - A network of capillaries that connects the arterioles to the venules

  
• Arterial End of Capillary Bed

  • Hydrostatic pressure is high due to pressure from artery and arteriole.
  • Because there is a greater hydrostatic pressure to osmotic pressure the net movement is outward.
  • Fluid is forced out through capillary walls

  Venous end of capillary bed

  • Hydrostatic pressure is low
  • Osmotic pressure is greater than hydrostatic pressure so net movement is inward
  • Fluid moves back into capillary due to water potential gradient.

  
• Fluid that does not return to capillaries is drained into the lymphatic system and returned to the blood stream.

  
• What 2 routes does tissue fluid take to get back to the blood?

  1. Net flow back into capillary due to high osmotic pressure
  2. Lymphatic system
• Haemoglobin has an affinity for oxygen
• • Each haemoglobin molecule can carry 4 oxygen molecules
  • This is a reversible reaction, when oxygen dissociates haemoglobin in the body tissue is becomes haemoglobin again.

  
• Haemoglobin + oxygen forms oxyhaemoglobin
• Partial pressure of oxygen (pO2) - a measure of oxygen concentration. High in the lungs, low in the muscle.
• Haemoglobin's affinity for oxygen depends on the partial pressure of oxygen.
• Haemoglobin picks up oxygen in the lungs (high pO2) and delivers it to respiring tissue (low pO2).
• • When haemoglobin has a high affinity it binds easily and dissociates slowly.
  • When haemoglobin has a low affinity for oxygen it binds slowly and dissociates easily.
• Oxygen dissociation curve - these show how saturated with oxygen haemoglobin is at any given partial pressure.

  • The curve is 's' shaped because when the first oxygen combines with the haemoglobin it becomes easier for more to join. But then towards the end it becomes harder for the final oxygen to join.
  • As the haemoglobin molecule approaches saturation it takes longer for the fourth oxygen molecule to bind due to the shortage of remaining binding sites, explaining the levelling off of the curve in the top right corner of the graph.

  
• Positive cooperativity - As one oxygen joins to the haemoglobin the affinity for oxygen increases
• Bohr effect

  • Haemoglobin gives up oxygen at high partial pressure of co2
  • When cells respire they produce co2, therefore increasing pCo2
  • This increases rate of oxygen dissociation and shifts dissociation curve to the right

  
• Foetal haemoglobin has a higher affinity for oxygen than maternal haemoglobin so oxygen dissociation curve is to the left.

  
• The ease with which haemoglobin binds and dissociates with oxygen can be described as its affinity for oxygen.
• Describe and explain the structure of the Aorta

  1. Small lumen - maintains pressure within organ
  2. Elastic fibres - recoils and expands to maintain blood pressure
  3. Thick smooth muscle wall - withstands high pressure of blood
  4. Smooth endothelium - Reduces friction within vessel
  5. Collagen - strong quaternary protein that prevents bursting
  6. Valves - ONLY in Aorta (semilunar valves) prevents backflow into left atrium.