Lecture 5 Flashcards
What is the nutritive blood supply to the lungs called?
Bronchial circulation
Describe bronchial circulation
Circulation supplied by the bronchial arteries to supply oxygenated blood to airway smooth muscle, nerves and lung tissue. It is part of the systemic circulation.
Where do the pulmonary arteries originate from?
The right ventricle of the heart
Describe the pulmonary circulation
It is a unique system that supplies the dense capillary network around the alveoli with deoxygenated blood and returns oxygenated blood to the heart.
Where does the pulmonary vein end?
In the left atrium
What type of system is the pulmonary circulation?
High flow, low pressure
Down what gradient does air diffuse during gas exchange?
The partial pressure gradient
What is the average PAO2?
100 mmHg
13.3 kPa
What is the average PACO2?
40 mmHg
5.3 kPa
What is the average PaO2?
100 mmHg
13.3 kPa
What is the average PaCO2?
40 mmHg
5.3 kPa
What is the average venous PO2?
40 mmHg
5.3 kPa
What is the average venous PCO2?
46 mmHg
6.2 kPa
Why is the rate of diffusion of CO2 not as low as expected in comparison to O2?
Because carbon dioxide is more water soluble than oxygen
What does fibrosis of the lungs do?
Restricts the stretching of the lungs so reduces compliance. It also reduces diffusion by creating a physical barrier.
What is Emphysema?
The destruction of barriers between alveoli creating large holes in the lungs, reducing surface area.
What is the primary cause of Emphysema?
Smoking
What is the ideal ratio of ventilation to perfusion?
1
What is the distribution of blood flow in the lungs influenced by?
Hydrostatic pressure and alveolar pressure
What is vascular resistance?
The resistance that must be overcome to push blood through the circulatory system
Why is blood flow low at the apex of the lungs?
Because arterial pressure is less than alveolar pressure so the arterioles are compressed increasing vascular resistance
Where is there the greatest amount of mismatch in ventilation and perfusion?
At the apex of the lungs
What local control mechanism can be used to try to keep ventilation and perfusion matched?
Blood vessels can constrict in areas of low ventilation and blood flow is diverted to areas of better ventilation
What happens when ventilation is less than blood flow?
PCO2 is increased and PO2 is decreased so blood flowing past does not get oxygenated
