Gas Exchange 2 Flashcards
What is a characteristic of pulmonary arteries and arterioles?
Thin
Compliant
Radius and length depends on inflation
Exposed to atmospheric (alveolar) pressure
What happens as pressure increases in pulmonary system?
Resistance decreases
What does decreased resitance faciliatte?
Large CO to lung for exercise
What makes the lung vulnerable to oedema formation?
Very large, thin walled, alveolar capillary bed to facilitate rapid gas exchange
How do you calculate perfusion pressure?
Pa - Pv
What happens when effective perfusion pressure = 0?
Capillaries collapse - negative pressure ventilation, not available for gas exchange
What part of the lung receives most blood flow?
Bottom of lung
What is a zone 2 region?
Pa > PA > Pv
Where is zone 2 found?
From apex down to approx 6cm above hilum
What gives gradient of pressure from top to bottom of lung?
Resistance increases at top as vessels are distensible and collapsible and the PA is low
What 3 things cause flow distribution?
Thin walled, collapsible vessels
Low intravascular pressures
Exposure of vessels to atmospheric pressure
What makes lung susceptible to oedema?
Thin walled and large surafce area
What are preventions to pulmonary oedema?
Low pressure circulation
Pulmonary lymphatic system - constant flow of lymph fluid
What course to lymphatic vessels follow?
Pulmonary veins to hilum
What contractile cells are present in pulmonary circulation?
Pericytes
