Human Phys 6.7 Flashcards
What is the blood volume in the lungs?
450 mL (9% of total blood volume in entire circulatory system)
How much of the blood volume of the lungs is in the pulmonary capillaries?
70mL (15%)
What happens to the remained of blood volume that is not in the pulmonary capillaries?
It is divided equally between the pulmonary arteries and the veins
What is the volume of systemic circulation?
9x greater than the pulmonary system
How does a shift from one system to another affect the pulmonary system?
Greatly
How does a shift of blood from one system to another affect the systemic circulation?
Only mildly (because of much higher volume)
How much blood can be expelled from the pulmonary circulatory system to the systemic circulation during periods of high thoracic and pulmonary pressures?
250 mL or blood (when someone blows a trumpet)
How can loss of blood from the systemic circulation by hemorrhage be compensated?
By the automatic shift of blood from the lungs into the systemic vessels
Systolic pulmonary artery pressure
25mmHg
Diastolic pulmonary artery pressure
8 mmHg
Mean pulmonary artery pressure
15 mmHg
Capillary pulmonary artery pressure
7 mmHg
What is blood flow through the lungs equal to?
CO
What do the pulmonary vessels act as under most conditions?
Passive, distensible tubes that enlarge with increasing pressure and narrow with decreasing pressure
What is important for adequate respiration to occur?
Blood to be distributed to those segments of the lungs where the alveoli are best oxygenated
What is the total surface area of the respiratory membrane in healthy adult males?
70 m^2
What occurs in systemic vessels when O2 is decreased?
Vasodilation
What occurs in pulmonary vessels when O2 is decreased?
Vasoconstriction
When is pulmonary blood flow autoregulation more pronounced?
When O2 concentration falls below 70% of normal
What is the pulmonary blood flow autoregulation important for?
Proper distribution of blood flow and avoidance of alveoli that are not adequately oxygenated
When does the pulmonary blood flow autoregulation fail?
When there is a widespread lung disease
What is the lowest point of the lungs in a normal upright adult?
30 cm below the highest point
What is the normal pressure difference in the lungs?
23 mmHg (15 above the heart and 8 below)
What is the pulmonary arterial pressure in the uppermost portion of the lungs in standing?
15 mmHg less than the pulmonary arterial pressure at the level of the heart
What is the pressure in the lowest portion of the lungs?
8 mmHg greater than the level of the heart
What is the flow of the blood in the lungs when standing at rest?
Little flow at top of lungs but 5x as much in the bottom
Zone 2 blood flow of lungs
Intermittent flow in the apices
Zone 3 blood flow of lungs
Continuous flow in all the lower areas
What is the lung like in supine?
No part of the lung is more than a few cm above the level of the heart
What is the blood flow in a normal person?
Entirely zone 3
How does blood flow increase during heavy exercise?
4-7 fold
How is the extra flow in the lungs accommodated for?
Increasing the number of open capillaries (sometimes as much as threefold)
Dilating all the capillaries and increasing the rate of flow through each capillary more than twofold
Increasing the pulmonary arterial pressure
What do the first two changes in the accommodation of blood flow cause?
Decrease in pulmonary vascular resistance so much that the pulmonary try arterial pressure rises very little (even during maximum exercise)
What does the ability of the lungs to accommodate greatly increased blood flow during exercise without increasing the pulmonary arterial pressure do?
Conserves energy of the right side of the heart and preventing the development of pulmonary edema
What is a shunt?
When a portion of blood flow is diverted from one place to another
Physiological shunt
About 2% of CO bypasses alveoli
Bronchial blood flow
Small amount of coronary blood flow drains directly into the LV
Explains why PaO2 will always be slightly lower than PAO2
Right to left shunt
Shunting the blood from the right heart to the left heart due to a defect in the ventricular wall
50% of CO can bypass lungs
Hypoxemia always occurs
Cannot be corrected by breathing 100% O2
Left to right shunt
More common
Do not cause hypoxemia
Oxygenated blood from the left heart is added back to the right heart
Right heart CO becomes larger than left heart CO
