Lung Ventilation and Perfusion Flashcards
What is ventilation?
The movement of gases in and out of the lungs through airways.
How is ventilation measured?
Measured as change in volume per unit time
What is perfusion?
The blood flow through any organs through blood vessels
How is perfusion measured?
Measured as flow of blood per unit time
Why are the apical alveoli 4x larger than basal alveoli?
Due to effect of gravity
What is effect on ventilation of apical alveoli being 4x larger than basal alveoli?
More ventilation at bottom of lungs. Basal alveoli can expand more than apical alveoli so basal regions have better ventilation.
Describe blood circulation (in one complete pump)
Vena cava –> right atrium –> right ventricle –> pulmonary artery –> lungs (oxygenated) –> pulmonary vein –> left atrium –> left ventricle –> aorta –> rest of body
What is systemic circulation?
Moves blood between heart and rest of body
Carries oxygenated blood from the left ventricle, through the arteries, to the capillaries in the tissues of the body. From the tissue capillaries, the deoxygenated blood returns to the heart.
What is pulmonary circulation?
Moves blood between heart and lungs.
Carries deoxygenated blood from right ventricle to the lungs and returns oxygenated blood to the left atrium and ventricle.
What are the 2 subcategories of pulmonary circulation?
- Functional supply
2. Structural supply
What is functional supply?
Oxygenation of venous blood (main blood supply to lungs)
What is structural supply?
Nutrition to lung tissue (AKA bronchial circulation)
- Bronchial artery from thoracic aorta
- Bronchial vein to superior vena cava
- Only 2% of cardiac output
What is the definition of cardiac output?
The amount of blood pumped through the circulatory system in one minute.
Stroke volume x heart rate
What is stroke volume?
Volume of blood pumped out of left ventricle per beat
What is a typical full cardiac output?
3-5 L/min
What is the blood pressure on right side compared to left?
Pressure in left is much higher. In right, vessels provide less resistance
As pulmonary artery goes through hilum into the lung it starts to divide. What does it divide into?
Each branch keeps splitting into smaller branches. The vessels travelling through lung parenchyma are called extra-alveolar vessels
What are the pulmonary arterioles/venules
Extension of the pulmonary artery which exits the heart from the right ventricle and then bifurcates into right and left.
Extension of the pulmonary vein which exits the lungs and travels to the left atrium.
How does gas exchange occur?
Capillary network forms on surface of alveolus with large surface area.
What happens when air has been oxygenated in lungs?
Oxygenated blood flows in to pulmonary venules which unite to form 4 large veins emptying in to left atrium
Where does gas exchange start?
Beyond terminal bronchioles (before this is just ‘conducting’ portion)
Starts at smaller arterioles
How does emphysema lead to poor gas exchange?
Chronic inflammation leads to widespread destruction of alveolar and capillaries and dilation of distal airway.
Poor gas exchange –> hypoxia
What is hydrostatic pressure?
The force exerted by the weight of a fluid due to gravity (maximum pressure at bottom of glass of water)