Respiration and Breathing 3 Flashcards
What does gravity influence
Ventilation and perfusion
Why is local matching of ventilation and perfusion important
To optimise gas exchange in lungs
Why is there better airflow at the base of the lungs
Due to pressure gradients
What is perfusion
Blood supply
What happens when there is no ventilation and good perfusion
Blood passing through the lung without coming into contact with alveolar air (right to left shunt)
What happens when there is good ventilation but no perfusion
Anatomically an increase in dead space or ventilated alveoli are not perfused
What mechanisms are in place to prevent alveolar ventilation rate matching perfusion rate
Achieved by modulation of blood flow.
What happens during hypoxia
When there is low PO2 vasoconstriction occurs. Blood is directed away from poorly ventilated areas. The response is very non-linear.
What happens during ventilation
The delivery of oxygen and removal of carbon dioxide.
Describe what happens to blood before perfusion
Blood from ventricle. Has high levels of CO2 and low levels of O2
How are alveoli adapted for gas exchange
Fluid lining of pulmonary surfactant which reduces pressure. Surrounded by a single cell capillary. Have a very small interstitial space (0.5 um)
What is transfer of oxygen influenced by
Diffusion across red blood cell membrane. Combination with haemoglobin.
What does combination of oxygen with haemoglobin do
Increases affinity and increases O2 capacity of blood.
Why is haemoglobin vital
Removes O2 so maintains conc gradient
What is the equation for oxygen and haemobglobin
O2 + Hb -> HbO2
Describe the Haemoglobin-O2 dissociation curve
% haemoglobin saturation (0-100)
PO2 of blood (mm Hg)
ml O2 per 100ml in blood (0-20)
Describe the Bohr Shift
In the presence of CO2 there is a change in the haemoglobin bidning of O2. An increase in PCO2 helps haemoglobin to release O2 where metabolsim is taking place
