Lecture 3: Pulmonary And Bronchial Circulations Flashcards
Blood flow varies throughout the lung as a result of (3 things):
- Low vascular pressures
- Gravity
- Distensible pulmonary vessels
Right ventricle ejection fraction of blood is distributed into ___ and equals ___
Lungs and equals LV cardiac output
Why is pulmonary blood pressure lower than systemic blood pressure?
Because the resistance to flow in the pulmonary system is one tenth of systemic circulation
Resistance to flow in the pulmonary system is ___ of systemic circulation
1/10th
Describe the wall of the pulmonary artery
- Thin walled (1/3 thickness of aorta)
- Very compliant
Pulmonary vessels are divided into ___ and ___
Alveolar and extra-alveolar vessels
Alveolar vessels are closely related to ___
Acini
What is acini?
Alveolocapillary network involved in gas exchange
Alveolar vessels are directly affected by…
Alveolar pressure
What collapses alveolar vessels during lung expansion?
High positive pressure
Alveolar capillaries can be ___ so that they contain ___
Compressed, no blood
What are the extra-alveolar vessels?
Arteries and veins which convey blood to-and-from the respiratory units
How does the structure of extra-alveolar vessels differ from alveolar vessels?
Larger vessels with thicker walls and substructure connective tissue
Are extra-alveolar vessels directly affected by pressures in the lung?
No
Do extra-alveolar vessels become compressed during positive pressure?
No
What pulls extra-alveolar vessels open during lung volume increases?
Surrounding lung tissue
What are the bronchial vessels?
- Vessels that contain oxygenated blood from systemic circulation
- Comprise 1-2% of cardiac output
- Empty into left atrium
Alveolar vessels provide ___ ___ to flow
Longitudinal resistance to flow
What resists pulmonary blood flow in the alveolar vessel network?
Alveolar vessel network dimensions and distensibility
Alveolar network dimensions are not regulated by ___ or ___
Autonomic or hormone control
Alveolar capillary walls contribute ___% of total resistance
40%
Alveolar arterioles contribute ___% of resistance
50%
In the body, arterioles are…
Major resistance vessels—75% of total systemic circulation resistance!
What does the resistance of capillary vessels depend on?
Lung conditions