Mass transport in animals Flashcards
describe the general pattern of blood circulation in a mamma
Oxygenated blood from left lung enter through the pulmonary vein to the left atrium.
Left atrium to left ventricle
Oxygenated blood leaves by the aorta to the head
Superior vena cava deoxygenated blood from the head and inferior vena cava deoxygenated blood to the right atrium
Right atrium to Right ventricle
Deoxygentated blood leaves by the pulmonary artery to the left lung through capillaries
Describe the pressure and volume changes and associated valve movements during the cardiac cycle that maintain a unidirectional flow of blood.
Atrial systole:
Atria contract. Pressure in atria higher than relaxed ventricles.
AV valves are OPEN (from diastole) / SL valves are CLOSED
Blood flows from atria into the ventricles (topping up).
Ventricular systole:
AV valves CLOSE as blood pressure rises.
When pressure is higher than arteries (pulmonary / aorta) SL valves open. Blood flows into the arteries.
Diastole:
Ventricle cease contraction and relax. Pressure drops and SL valves CLOSE. Arteries recoil.
When pressure drops below atrial pressure the AV valves RE-OPEN. Blood flows passively into ventricles.
Structure of artery
Thick muscle layer
Elastic layer
Large overall wall thickness
No valves
Tough fibrous outer layer
Thin endothelial lining
Function of artery
Maintain high pressure flow to tissues (away from the heart)
Muscle can contract
Elastic can stretch and recoil
Resists pressure changes from inside and outside
Smooth cells which reduce friction
Structure of arterioles
Smaller and more numerous than arteries
Relatively thicker muscle layer
Relatively thinner elastic layer
Tough fibrous outer layer
Thin endothelial lining
Function of arterioles
Vasoconstriction / dilation controls blood flow to the capillaries
Resists pressure changes from inside and outside
Smooth cells which reduce friction
Structure of veins
Small overall wall thickness
Thin muscle and elastic layer
Contain valves
Tough fibrous outer layer
Thin endothelial lining
Function of veins
Slow, low pressure transport of blood (from tissues back to the heart)
Valves prevent back flow
Resists pressure changes from inside and outside
Smooth cells which reduce friction
Structure of capillaries
Walls made from endothelial cells
Very numerous and highly branched
Narrow diameter
Narrow lumen
Tiny pores between endothelial cells
Function of capillaries
Very thin which reduces the diffusion distance between the blood and the tissue cells
Very large surface area for exchange
Squeeze between tissues so all cells very close to a capillary / reduces diffusion distance
Red blood cells are closer to cells / reduces diffusion distance
Formation of tissue fluid
Explain the pressure changes that occur as blood flows through the circulatory system.
Arteries - high pressure due to left ventricle and smaller TOTAL cross sectional area.
Arterioles - smaller vessels but much larger TOTAL cross sectional area, pressure drops.
Arteries / arterioles - pressure fluctuates due to RECOIL
Capillaries - very large cross sectional area, branched and higher resistance, one-cell thick so no recoil
Venules / veins - relatively large lumen
Can you write the equation for ‘cardiac output’?
Cardiac output ((dm3 min-1) = Stroke volume (dm3) x Heart rate (mins)
Cardiac output is the total volume of blood pumped by the left ventricle in one minute.
Heart rate = rate heart beats per minute
Stroke volume = volume of blood pumped out per cardiac cycle
Describe the formation of tissue fluid and its return to the circulatory system.
At the arterial end of the capillary bed, hydrostatic pressure is higher than
osmotic pressure and so water and small soluble molecules in the blood
plasma are forced through the capillary walls (fenestrae), forming tissue
fluid between the cells. Larger, dissolved proteins and cells in the plasma
are too large to be forced out.
Metabolites and cell products can be exchanged between the tissue fluid
and cells.
Blood pressure falls along the capillary because of friction/resistance of
the walls and reduced volume of blood. At the venous end of the capillary
bed, osmotic pressure of the blood is higher than the hydrostatic pressure
and so most of the water from tissue fluid moves back into blood
capillaries (down its water potential gradient).
The remainder of the tissue fluid is returned to the blood, via lymph
vessels.
Relate the structure of haemoglobin to its function in the transport of oxygen.
Quaternary structure - 2 alpha globins and 2 beta globins
Each subunit has a haem group
Each haem group has an iron ion, Fe2+
Oxygen can bind reversibly with haemoglobin
Oxygen binds to haemoglobin at respiratory surfaces
Oxygen dissociates (unloads) at respiring tissues
Detail the loading, transport and unloading of oxygen in relation to the oxyhaemoglobin dissociation curve.
Higher partial pressure of oxygen (gas concentration) more oxygen binds to haemoglobin.
Lower partial pressure of oxygen less oxygen binds to haemoglobin.
Lungs (alveoli):
High pO2 therefore haemoglobin becomes fully saturated with oxygen (oxyhaemoglobin).
Respiring tissues:
Tissues are using oxygen in aerobic respiration so the pO2 in tissues is lower.
Oxygen dissociates from oxyhaemoglobin, into the tissues.
