Flashcards in Session 9 Deck (56)
What are the 2 circulations in the lungs?
What is the function of the Bronchial lung circulation.
Part of the systemic circulation and meets the metabolic needs of the lungs
What is the function of the pulmonary lung circulation?
Blood supply to the alveoli and is needed for gas exchange.
What is the pressure in the right atrium?
What is the pressure in the right ventricle?
What is the pressure in the pulmonary artery?
What is the pressure in the left atrium?
What is the pressure in the left ventricle?
What is the pressure in the aorta?
What is the mean arterial, capillary and venous pressure in the pulmonary circulation?
Arterial - 12-15 mmHg
Capillary - 9-12 mmHg
Venous - 5 mmHg
How does the pulmonary circulation ensure low resistance?
Has short and wide vessels
Has many capillaries in parallel
Has very little smooth muscle
How does the pulmonary circulation ensure efficient gas exchange?
Has a large surface area due to high density of capillaries in th alveolar wall
Thin layer of tissue to create a short diffusion pathway
What does the alveoli need for efficient oxygenation?
Must match the ventilation with perfusion
An optimal Q : V ratio is 0.8 for one alveoli.
How can the pulmonary circulation ensure there is an optimal Q : V ratio?
Hypoxia pulmonary vasoconstriction - diverting blood away from the alveoli that are not well ventilated. Possibly due to disease.
What can chronic hypoxia vasoconstriction cause?
Right ventricular hypertrophy because increase in vault resistance --> pulmonary hypertension --> right ventricle having to work harder.
When can chronic hypoxia vasoconstriction occur?
At high altitudes
Consequence of lung disease
What is capillary transit time?
How long it takes for red blood cells to move along a vessel. (Flow)
When can capillary transit time decrease?
Extra point - How?
During exercise. There is NO compromise to gas exchange.
Extra point - an increase in cardiac output --> increase in pulmonary arterial pressure --> opening of apical capillaries --> increase O2 uptake of lungs --> increased blood flow --> decreased capillary transit time.
What determines fluid formation?
What influences capillary hydrostatic pressure more, arterial or venous pressure in the systemic circulation?
Venous pressure in systemic circulation.
What pressure causes fluid to leave pulmonary capillaries?
What pressure causes fluid to enter pulmonary capillaries?
Colloid oncotic pressure.
What happens if the hydrostatic pressure is too high and too much lymph is formed in the lung?
It will impair gas exchange
What is the typical movement (in/out) of fluid along a pulmonary capillary?
More fluid moves out at the arterial end
More fluid moves in at the venous end
At what atrial pressure will you get oedema?
When could you have high pressure in theft atrium?
Mitral valve stenosis.
Left ventricular failure.
What can relieve the symptoms of pulmonary oedema?
Diuretics as they reduce the blood volume which reduces hydrostatic pressure.
How does posture effect pulmonary oedemas?
The fluid is at the base of the lung when standing and spread out over the lung when lying down
How does the effect of hydrostatic pressure on pulmonary vessels vary with gravity?
Top vessels collapse during diastole
Vessels in line with the heart continuously open
Vessels at the bottom distend