Physiology: Blood Supply, Gas Exchange, Ventilation and Perfusion Flashcards
What is the blood supply to the lungs?
Bronchial Circulation
Pulmonary Circulation
What is bronchial circulation? (3)
Nutritive
Supplied via bronchial arteries
Arising from the systemic circulation and supplies oxygenated blood to airway smooth muscle, nerves and tissue
What is the pulmonary circulation? (4)
Consists of L and R pulmonary arteries anf dense capillary network surrounding alveoli
Carries entire cardiac output from RV
High flow, low pressure
Returns oxygenated blood to the LA
What does A stand for in pressure?
Alveolar
What does a stand for in pressure?
Arterial Blood
What does v stand for in pressure?
Mixed venous blood
What are the factors of diffusion across the membrane? (5)
Directly proportional too PP gradient
Directly proportional to gas solubility
Directly proportional to available surface area
Inversly Proportional to thickness of membrane
Most rapid over short distances
What is the PP of oxygen and carbon dioxide in alveoli and systemic arterial blood?
PO2 - 100mmHg
PCO2 - 40mmHg
What is the PP pf O2 and CO2 in pulmonary arterial blood and tissues?
PO2 - 40mmHg
PCO2 - 46mmHg
How alveoli aid gas exchange?
They have a large surface area
Thin membrane wall
What happens to gas exchange in Emphysema?
Normal or Low PO2 in alveoli
Low PO2 in arterial blood
What happens to alveoli in emphysema?
Alveoli destroyed causing reduced surface area
What to alveoli in Fibrotic Lung Disease?
Thickened alveolar membrane
Loss of compliance reduces alveolar ventilation
What happens to the gas exchange in fibrotic lung disease?
PO2 in alveoli is normal or low
PO2 in arterial blood is low
What happens to alveoli in Pulmonary Oedema?
Interstitial fluid between alveoli and capillaries is increased increasing the distance
What happens to gas exchange in Pulmonary Oedemas?
PO2 in alveoli is normal
PO2 in arterial blood is low
What happens to alveoli in asthma?
Increased airway resistance decreases airway ventilation
What happens to gas exchange on asthma?
PO2 in alveoli is low
PO2 in arterial blood is low
What is the relationship observed between blood flow and ventilation at the base of the lung?
Blood flow is higher than ventilation as arterial pressure exceeds alveolar pressure
Blood flow > ventilation
What is compressed at the base of the lung?
The alveoli
What is the relationship observed between blood flow and ventilation at the apex of the lung?
Blood flow is low as arterial pressure is less than alveolar pressure
Ventilation> Blood flow
What is compressed at the apex of the lung?
Arterioles
Where does the majority of mismatch between ventilation and perfusion take place in the lung?
Apex
What is the definition of shunt?
passage of blood through poorly ventilated areas of the lungs
Ventilation < Perfusion
What is Alveolar Dead Space?
Alveoli that are well ventilated but not perfused
Ventilation > Perfusion
What does the pulmonary circulation do when a shunt occurs?
Constriction of arterioles surrounding poorly ventilated alveoli due to hypoxia
Broncho dilation of arterioles surrounding better ventilated alveoli
What happens the pulmonary circulation when alveolar dead space occurs?
Increase in bronchial constriction due to the decrease in PCO2 and pulmonary vasodilation due to the increase in PO2
What is anatomical dead space?
air in the conducting zones of the respiratory tract and therefore not taking part in gas exchange
What is Physiological Dead Space?
Alveolar Dead Space + Anatomical Dead Space
