essay questions

• Give ana account for red blood cells as a component of blood

  1. Red blood cells main role is to carry oxygen
  2. They are extremely small biconcave discs
  3. Thus have a relatively large surface area to volume ratio
  4. Packed with haemoglobin molecules/mature cells have no nucleus
  5. Oxygen combines with haemoglobin forming oxyhaemoglobin
  6. At high p.p. O2 haemoglobin has a high affinity for O2
  7. At low p.p.O2 haemoglobin has a low affinity for O2 (unloads oxygen)
  8. Oxygen is delivered to tissues with low p.p.02 and high p.p.CO2
• Give a account for white blood cells as components of blood

  1. Provide defence against infection
  2. 3 types including lymphocytes, polymorphs and monocytes
  3. Lymphocytes involved in antibody production
  4. T-lymphocytes are involved in cell-mediated immunity and the destruction of
  5. foreign and infected cells
  6. Polymorphs/monocytes are phagocytic cells
  7. Ingest invading bacteria that have been marked by antibodies
• Give a account for platelets as components of blood

  1. Involved in blood clotting
  2. Platelets activated when passing through damaged blood vessels
  3. Thromboplastin is released when tissues are damaged
  4. Thromboplastin converts prothrombin to thrombin
  5. Results in conversion of fibrinogen to fibrin
  6. Network of fibrin traps red blood cells
  7. Forms a scab which prevents further blood loss and infection
• Give an account of the waves of excitation, the pressure changes and the opening and closing of valves during the cardiac cycle. From the Atrial systole

  1. Cardiac muscle cells are myogenic
  2. Excitation wave is initiated at SA-node
  3. Electrical impulses move across atrial walls causing atrial systole
  4. Contraction increases pressure in the atria
  5. Forcing blood into ventricles
  6. Electrical impulses cannot pass directly to the ventricle due to sheet of non-
  7. conducting tissue between atria and ventricle
  8. Ensure delay between atrial and ventricular systole
• account of the waves of excitation, pressure changes and opening+ closing of valves during the cardiac cycle. From the ventricular systole


  AV-node picks up the electrical impulses from the atrial muscle

  Impulses pass along the Bundle of His and Purkinje fibres in ventricle wall

  Ventricle contracts from base up

  Ventricular systole increases pressure within the ventricles

  Blood is forced against the AV-valves which close

  Chordae tendinae prevent the AV-valves blowing inside out

  Semilunar valves forced open

  Blood leaves ventricles and enters pulmonary artery/aorta
• account of the waves of excitation, pressure changes and opening+ closing of valves during the cardiac cycle from diastole.

  1. Ventricular diastole follows
  2. With decreased pressure in ventricles
  3. Semilunar valve closes
  4. Backflow of blood into ventricles prevented
  5. Blood returns to the atria from the vena cava of pulmonary veins
  6. Increases atrial pressure
  7. Causes AV-valves to push open during atrial diastole
  8. Blood moves from atria to ventricle
• account of the structure of haemoglobin. role in absorbing oxygen

  from.

  1. Haemoglobin is a conjugated protein/contains haem group
  2. Haem is an iron-containing prosthetic group
  3. Each haemoglobin molecule has four haem groups each capable of carrying
  4. O2
  5. % saturation of haemoglobin with O2 depends p.p. O2
  6. Reference s-shaped dissociation curve
  7. Initial binding of O2 facilitates subsequent binding
  8. In the lungs p.p.O2 is high
  9. At high pp O2 oxyhaemoglobin forms readily
• Explain how oxygen is supplied to strenuously exercising muscle.


  1. Strenuously exercising muscle has a high rate respiration
  2. High rate respiration consumes O2/reduces pp O2
  3. Reduced pp O2 causes dissociation/unloading of oxygen from haemoglobin
  4. Increased resp also increases pp CO2
  5. Which reduces haemoglobins affinity for O2
  6. So more O2 is released/unloaded
  7. Called the Bohr effect
  8. Bohr effect is also caused by rise in temperature
  9. Muscle may contain myoglobin
  10. Very high affinity for O2/acts as O2 store
  11. Releasing O2 when pp O2 becomes very low
  12. Allowing aerobic respiration to continue
• Give an account of the adaptations and roles of arteries

  1. Three layers
  2. Carry blood under high pressure
  3. Have much elastic tissue to withstand pressure/stretch and recoil
  4. Carry blood away from the heart
  5. Contain much muscle tissue
  6. To control blood flow to organs (vasoconstriction)
  7. As a result have a thick wall/tunica media
  8. Small lumen helps maintain pressure
• Give an account of the adaptations and roles of veins

  1. Wall consists of pavement endothelium only
  2. Thin wall reduces diffusion distance
  3. Represent a huge surface area
  4. Tissue fluid formed arterial end
  5. Due to high (hydrostatic) pressure
  6. Supply metabolites to the tissues
  7. Proteins too large to leave blood stream/fluid reabsorbed at venule end
  8. Very small lumen assists diffusion
• Give an account of the adaptions and roles of capillaries

  1. Three layers
  2. Carry blood back to the heart
  3. Under low pressure
  4. Have a large lumen and valves (one-way flow)
  5. Thin wall/less muscle due to low pressure of blood
  6. Tunica media contains less fibrous tissue