3.4 Mass Transport in Animals Flashcards
What is haemoglobin?
• Protein with a quaternary structure found in red blood cells
• Each chain contains a haem group containing an iron iron
• Associates/loads oxygen at high pO2, forming oxyhaemoglobin
• Dissociates/unloads oxygen at low pO2
Why is the oxyhaemoglobin curve S shaped?
• Cooperative binding
• Binding of first oxygen changes tertiary structure of haemoglobin
• Uncovering haem group binding sites, making it easier for oxygen to bind
What is the Bohr effect?
• Due to increased rate of respiration, concentration of CO2 in the blood increases
• Lowers blood pH
• Alters tertiary structure of haemoglobin, reducing its affinity for oxygen
• So more oxygen unloads at respiring cells
What is meant by a double circulatory system?
Blood passes through the heart twice for every circuit around the body
Right side of heart
Vena cava (deoxygenated blood from respiring tissues to heart)
Right atrium
Right ventricle
Pulmonary artery (deoxygenated blood from heart to lungs)
Left side of heart
Pulmonary vein (oxygenated blood from lungs to heart)
Left atrium
Left ventricle
Aorta (oxygenated blood from heart to respiring tissues)
Which blood vessels carry oxygenated blood to heart muscle?
Coronary arteries
Why is the wall of the left ventricle thicker than the right?
• Thicker muscle to contract with greater force
• To generate higher pressure to pump blood around entire body
Atrial systole
• Atria contract
• AV valves open when pressure in atria exceeds pressure in ventricles
• SL valves shut as pressure in arteries exceeds pressure in ventricles
• So blood pushed into ventricles
Ventricular systole
• Ventricles contract
• AV valves shut when pressure in ventricles exceeds pressure in atria
• SL valves shut as pressure in ventricles exceeds pressure in arteries
• So blood pushed out through arteries
Diastole
• Atria and ventricles relax
• AV valves open when pressure in atria exceeds pressure in ventricles
• SL valves shut as pressure in arteries exceeds pressure in ventricles
• So blood fills atria and flows into ventricles
How is cardiac output calculated?
Cardiac output = stroke volume x heart rate
How are arteries structured?
• Thick wall to withstand high pressure
• Thick smooth muscle tissue so can contract to maintain blood flow
• Thick elastic tissue so can stretch and recoil to reduce pressure surges
• Smooth endothelium to reduce friction
• Narrow lumen to maintain high pressure
How are veins structured?
• Winder lumen so less resistance to blood flow
• Little elastic and muscle tissue as blood pressure lower
• Valves to prevent backflow of blood
How are capillaries structured?
• One cell thin endothelium so short diffusion distance
• Large network of branched capillaries / capillary bed so increased surface area
• Narrow lumen so reduced rate of blood flow so more time for diffusion
• Pores between cells, allowing larger substances through
How is tissue fluid formed?
• Higher hydrostatic pressure inside capillaries than tissue fluid
• Forcing water and dissolved substances out capillary
• Larger plasma proteins remain in capillary
How is tissue fluid returned?
• Hydrostatic pressure reduces as fluid leaves capillary
• Increased concentration of plasma proteins lowers water potential in capillary
• Water enters capillary from tissue fluid by osmosis
• Excess water taken up by lymph capillaries
