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Questions and Answers
What is the typical range of wedge pressure in relation to left atrial pressure?
What is the typical range of wedge pressure in relation to left atrial pressure?
What could cause an increase in pulmonary wedge pressure?
What could cause an increase in pulmonary wedge pressure?
Approximately what percentage of the total blood volume does the blood volume of the lungs represent?
Approximately what percentage of the total blood volume does the blood volume of the lungs represent?
How can wedge pressure measurements be clinically useful?
How can wedge pressure measurements be clinically useful?
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Which condition is associated with increased pulmonary wedge pressure?
Which condition is associated with increased pulmonary wedge pressure?
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What physiological change occurs in the small wedged artery under examination?
What physiological change occurs in the small wedged artery under examination?
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What is the consequence of a rise in pulmonary capillary pressure?
What is the consequence of a rise in pulmonary capillary pressure?
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Which measurement relationship reflects changes due to congestive heart failure?
Which measurement relationship reflects changes due to congestive heart failure?
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What is the approximate volume of blood in the pulmonary capillaries?
What is the approximate volume of blood in the pulmonary capillaries?
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Which system receives blood expelled from the pulmonary circulation when pressure in the lungs increases?
Which system receives blood expelled from the pulmonary circulation when pressure in the lungs increases?
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Under normal physiological conditions, how does the blood volume in the lungs typically change?
Under normal physiological conditions, how does the blood volume in the lungs typically change?
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What physiological activity can lead to a significant increase in pulmonary blood pressure?
What physiological activity can lead to a significant increase in pulmonary blood pressure?
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What occurs in the pulmonary circulatory system when a person blows air hard enough to raise lung pressure?
What occurs in the pulmonary circulatory system when a person blows air hard enough to raise lung pressure?
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Which of the following statements about the distribution of pulmonary blood volume is correct?
Which of the following statements about the distribution of pulmonary blood volume is correct?
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What impact does blowing forcefully have on the volume of blood in the pulmonary circulatory system?
What impact does blowing forcefully have on the volume of blood in the pulmonary circulatory system?
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How does blood volume regulation in the lungs typically manifest under pathological conditions?
How does blood volume regulation in the lungs typically manifest under pathological conditions?
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What can happen to pulmonary capillary pressure during acute cardiac pathology?
What can happen to pulmonary capillary pressure during acute cardiac pathology?
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Which pressure measurement reflects the mean pressure in the pulmonary arteries during systole?
Which pressure measurement reflects the mean pressure in the pulmonary arteries during systole?
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What happens to the pulmonary vessels when there is an increase in pressure?
What happens to the pulmonary vessels when there is an increase in pressure?
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Which condition is most likely to cause vasoconstriction in the pulmonary arteries?
Which condition is most likely to cause vasoconstriction in the pulmonary arteries?
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During rest, where is the majority of blood flow located in the lungs of an upright person?
During rest, where is the majority of blood flow located in the lungs of an upright person?
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How does hypoxia affect calcium ion concentration in pulmonary arteries?
How does hypoxia affect calcium ion concentration in pulmonary arteries?
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What effect does exercise have on blood flow in the lungs?
What effect does exercise have on blood flow in the lungs?
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What occurs when there is a decreased PO2 in the tissue surrounding poorly ventilated alveoli?
What occurs when there is a decreased PO2 in the tissue surrounding poorly ventilated alveoli?
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What happens to blood flow distribution in the pulmonary system when alveolar O2 concentration decreases below 70% of normal?
What happens to blood flow distribution in the pulmonary system when alveolar O2 concentration decreases below 70% of normal?
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How does left-sided heart failure affect pulmonary dynamics?
How does left-sided heart failure affect pulmonary dynamics?
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What is a potential consequence of increased pulmonary capillary pressure?
What is a potential consequence of increased pulmonary capillary pressure?
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What mechanism regulates pulmonary blood flow distribution?
What mechanism regulates pulmonary blood flow distribution?
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How does pulmonary edema typically occur in the context of cardiac issues?
How does pulmonary edema typically occur in the context of cardiac issues?
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What occurs in the lungs during low local PO2 concentration?
What occurs in the lungs during low local PO2 concentration?
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What is the primary response of pulmonary vessels to increased alveolar oxygen concentrations?
What is the primary response of pulmonary vessels to increased alveolar oxygen concentrations?
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What is the role of hydrostatic pressure gradients in the lungs?
What is the role of hydrostatic pressure gradients in the lungs?
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What impact does the dumping of fluid from the interstitial space into alveoli have?
What impact does the dumping of fluid from the interstitial space into alveoli have?
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What is the primary consequence of increased permeability of capillary membranes in the pleural cavity?
What is the primary consequence of increased permeability of capillary membranes in the pleural cavity?
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Which factor primarily influences osmotic pressure in the pulmonary capillaries?
Which factor primarily influences osmotic pressure in the pulmonary capillaries?
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How does infection contribute to pulmonary edema mechanisms?
How does infection contribute to pulmonary edema mechanisms?
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What is a key effect of hypoxic pulmonary vasoconstriction?
What is a key effect of hypoxic pulmonary vasoconstriction?
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What is primarily regulated to maintain proper blood volume in the pulmonary system?
What is primarily regulated to maintain proper blood volume in the pulmonary system?
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Which process describes the movement of fluid from the bloodstream into the interstitium?
Which process describes the movement of fluid from the bloodstream into the interstitium?
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What role does hydraulic conductance play in lung endothelial function?
What role does hydraulic conductance play in lung endothelial function?
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What effect does excessive transudation have on pulmonary edema?
What effect does excessive transudation have on pulmonary edema?
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Which physiological change directly contributes to cardiac pathology affecting pulmonary circulation?
Which physiological change directly contributes to cardiac pathology affecting pulmonary circulation?
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During which condition is it most likely for capillary membranes in the lungs to increase in permeability?
During which condition is it most likely for capillary membranes in the lungs to increase in permeability?
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What is the primary function of the pulmonary veins in the circulatory system?
What is the primary function of the pulmonary veins in the circulatory system?
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Which statement describes a characteristic of the pulmonary artery compared to the aorta?
Which statement describes a characteristic of the pulmonary artery compared to the aorta?
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How do lymph vessels contribute to pulmonary health?
How do lymph vessels contribute to pulmonary health?
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What anatomical feature marks the beginning of lymph vessels in the lungs?
What anatomical feature marks the beginning of lymph vessels in the lungs?
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What happens to blood volume in the lungs during gas exchange in the alveoli?
What happens to blood volume in the lungs during gas exchange in the alveoli?
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What type of blood do the bronchial arteries supply to the lungs?
What type of blood do the bronchial arteries supply to the lungs?
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Which of the following is true about the flow of blood in the pulmonary circulation?
Which of the following is true about the flow of blood in the pulmonary circulation?
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How does the pressure in the bronchial arteries compare to the aortic pressure?
How does the pressure in the bronchial arteries compare to the aortic pressure?
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What is the primary function of the low-pressure, high-flow circulation in the lungs?
What is the primary function of the low-pressure, high-flow circulation in the lungs?
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What portion of the total cardiac output do the bronchial arteries represent?
What portion of the total cardiac output do the bronchial arteries represent?
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What occurs when left atrial pressure increases in relation to pulmonary circulation?
What occurs when left atrial pressure increases in relation to pulmonary circulation?
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How does the rate of edema formation relate to pulmonary capillary pressure?
How does the rate of edema formation relate to pulmonary capillary pressure?
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Which system is primarily responsible for returning excess fluid from lung tissues?
Which system is primarily responsible for returning excess fluid from lung tissues?
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What is a potential consequence of increased pulmonary capillary pressure?
What is a potential consequence of increased pulmonary capillary pressure?
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Which factor primarily influences the rate of fluid loss into lung tissues?
Which factor primarily influences the rate of fluid loss into lung tissues?
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What happens to edema formation rate when venous system pressure decreases?
What happens to edema formation rate when venous system pressure decreases?
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What component of the pulmonary circulation is directly affected by increased left atrial pressure?
What component of the pulmonary circulation is directly affected by increased left atrial pressure?
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Which of the following most directly leads to edema fluid accumulation in pulmonary tissues?
Which of the following most directly leads to edema fluid accumulation in pulmonary tissues?
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How does pulmonary artery pressure affect fluid dynamics in the lungs?
How does pulmonary artery pressure affect fluid dynamics in the lungs?
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Which condition is likely to be observed with elevated left atrial pressure in terms of fluid dynamics?
Which condition is likely to be observed with elevated left atrial pressure in terms of fluid dynamics?
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The pulmonary veins empty their effluent blood into the right atrium.
The pulmonary veins empty their effluent blood into the right atrium.
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The bronchial arteries supply oxygenated blood at a pressure that is lower than the aortic pressure.
The bronchial arteries supply oxygenated blood at a pressure that is lower than the aortic pressure.
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The high-pressure, low-flow circulation supplies blood to the bronchial tree and supporting lung tissues.
The high-pressure, low-flow circulation supplies blood to the bronchial tree and supporting lung tissues.
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The low-pressure, high-flow circulation is responsible for oxygenating blood in the alveolar capillaries.
The low-pressure, high-flow circulation is responsible for oxygenating blood in the alveolar capillaries.
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Blood from the bronchial arteries returns to the right atrium after supplying the lungs.
Blood from the bronchial arteries returns to the right atrium after supplying the lungs.
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The average systolic pressure in the right ventricle is about 50 mm Hg.
The average systolic pressure in the right ventricle is about 50 mm Hg.
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Pulmonary arteries have a larger diameter than systemic arteries.
Pulmonary arteries have a larger diameter than systemic arteries.
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The wedge pressure measured in the pulmonary artery is approximately 15 mm Hg.
The wedge pressure measured in the pulmonary artery is approximately 15 mm Hg.
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The compliance of the pulmonary arterial tree is similar to that of the entire systemic arterial tree.
The compliance of the pulmonary arterial tree is similar to that of the entire systemic arterial tree.
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During systole, the pressure in the pulmonary artery is lower than the pressure in the right ventricle.
During systole, the pressure in the pulmonary artery is lower than the pressure in the right ventricle.
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The average left atrial pressure in a recumbent person is approximately 8 mm Hg.
The average left atrial pressure in a recumbent person is approximately 8 mm Hg.
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Blood flow through the lungs is equal to cardiac output.
Blood flow through the lungs is equal to cardiac output.
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It is easy to measure left atrial pressure directly using a catheter.
It is easy to measure left atrial pressure directly using a catheter.
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The pulmonary wedge pressure can provide an estimate of left atrial pressure.
The pulmonary wedge pressure can provide an estimate of left atrial pressure.
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Peripheral factors control pulmonary blood flow by influencing heart rate.
Peripheral factors control pulmonary blood flow by influencing heart rate.
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The pulmonary venous pressure can fluctuate between 2 and 10 mm Hg.
The pulmonary venous pressure can fluctuate between 2 and 10 mm Hg.
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A shift of blood from the systemic to the pulmonary circulation usually causes significant effects on the systemic system.
A shift of blood from the systemic to the pulmonary circulation usually causes significant effects on the systemic system.
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Cardiac output and pulmonary blood flow are independent of each other.
Cardiac output and pulmonary blood flow are independent of each other.
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The mean pressure in the left atrium is higher when a person is standing compared to when they are recumbent.
The mean pressure in the left atrium is higher when a person is standing compared to when they are recumbent.
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Match the following terms with their descriptions related to pulmonary circulation:
Match the following terms with their descriptions related to pulmonary circulation:
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Match the following pressures with their associated phases in the pulmonary circulation:
Match the following pressures with their associated phases in the pulmonary circulation:
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Match the physiological conditions with their effects on pulmonary blood volume:
Match the physiological conditions with their effects on pulmonary blood volume:
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Match the following structures with their roles in the respiratory system:
Match the following structures with their roles in the respiratory system:
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Match the following concepts related to pulmonary circulation:
Match the following concepts related to pulmonary circulation:
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Match the terms with their descriptions related to pulmonary circulation:
Match the terms with their descriptions related to pulmonary circulation:
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Match the factors with their roles in pulmonary blood flow:
Match the factors with their roles in pulmonary blood flow:
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Match the physiological changes with their effects:
Match the physiological changes with their effects:
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Match the components with their functions in the pulmonary system:
Match the components with their functions in the pulmonary system:
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Match the concepts related to pulmonary blood flow distribution:
Match the concepts related to pulmonary blood flow distribution:
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Study Notes
Pulmonary Wedge Pressure
- Wedge pressure is similar to left atrial pressure because blood flow is stopped in the wedged artery.
- Wedge pressure is higher than left atrial pressure by 2-3 mm Hg.
- Pulmonary wedge pressure can be used to estimate left atrial pressure changes in patients with congestive heart failure.
Pulmonary Blood Volume
- Pulmonary blood volume: about 450 ml.
- About 9% of the total blood volume.
- 70 ml of blood volume occurs in the pulmonary capillaries.
- Pulmonary arteries and veins contain equal amounts of blood.
### Lungs as a Blood Reservoir
- Lungs can accommodate blood volume variations as much as half normal to twice normal.
- For example, blowing a trumpet expels 250 ml of blood from pulmonary circulatory system into systemic circulation
### Regulation of Blood Flow
- Decreased alveolar oxygen (PO2) reduces local blood flow.
- Hypoxia causes vasoconstriction of arterioles and diverts blood flow to well-ventilated alveoli.
- This mechanism helps regulate pulmonary blood flow distribution and ensures adequate oxygenation.
Effect of Hydrostatic Pressure Gradients on Pulmonary Blood Flow
- Blood flow is greater in lower regions of the lungs due to gravity.
- During exercise, blood flow increases at all lung levels.
- Most blood flow occurs at the bottom of the lungs when at rest.
- Blood flow at the top of the lungs is minimal at rest.
Pulmonary Circulation
- The lung has two circulations:
- High-pressure, low-flow circulation: supplies systemic arterial blood to trachea, bronchial tree, supporting tissues, and outer coats of pulmonary arteries and veins
- Low-pressure, high-flow circulation: supplies venous blood to alveolar capillaries where oxygen is added, and carbon dioxide is removed
Bronchial Vessels
- Bronchial arteries originate from the thoracic aorta and supply systemic arterial blood to the lung
- Bronchial arteries supply the supporting tissues like connective tissue, septa, and large and small bronchi.
- Bronchial arterial blood is oxygenated in contrast to the partially deoxygenated blood in the pulmonary arteries.
Lymphatics in the Lung
- Lymph vessels are present in all supporting tissues of the lung, beginning in the connective tissue spaces surrounding the terminal bronchioles
- Particulate matter entering the alveoli is partly removed by lymph vessels
- Plasma protein leaking from lung capillaries is also removed from the lung tissues by lymph vessels, to prevent pulmonary edema
Pressures in the Pulmonary System
- Pulmonary arteries have a wall thickness one-third that of the aorta
- The pulmonary artery divides into right and left main branches that supply blood to the two respective lungs
Pulmonary Edema
- Pulmonary edema occurs due to:
- An increase in pulmonary capillary pressure
- A decrease in plasma colloid osmotic pressure which reduces the return of fluid from the interstitial space
Pleural Fluid
- A thin layer of mucoid fluid lies between the parietal and visceral pleurae and acts as a lubricant
- The negativity of the pleural fluid pressure pulls the lungs against the parietal pleura of the chest cavity
Pleural Effusion
- Pleural effusion is an excess accumulation of fluid in the pleural cavity
- Causes of pleural effusion:
- Blockage of lymphatic drainage from the pleural cavity
- Cardiac failure, resulting in high peripheral and pulmonary capillary pressures
- Reduced plasma colloid osmotic pressure leading to excessive transudation
- Infection or any other cause of inflammation of the pleural cavity, increasing capillary membrane permeability and fluid leak
Pulmonary Circulation
- Two separate circulatory systems operate within the lungs: a high-pressure, low-flow circulation and a low-pressure, high-flow circulation.
- The high-pressure system supplies systemic arterial blood to the trachea, bronchial tree, supporting lung tissues, and the outer coats of pulmonary arteries and veins.
- The low-pressure system delivers venous blood from the body to the alveolar capillaries for gas exchange.
- The pulmonary arteries are short and have larger diameters than systemic arteries, contributing to their high compliance, allowing them to accommodate the right ventricle's output.
Bronchial Vessels
- Bronchial arteries branch from the thoracic aorta, constituting 1-2% of cardiac output and deliver oxygenated systemic blood to lung tissues.
- This blood supports connective tissue, septa, and large and small bronchi.
- After traversing lung tissues, the deoxygenated blood drains into the pulmonary veins and enters the left atrium.
Pulmonary Arterial Pressures
- The pressure in the pulmonary artery is essentially equal to the right ventricle's pressure during systole.
- Normal systolic pressure in the right ventricle averages around 25 mm Hg, with diastolic pressure averaging 0-1 mm Hg.
Pulmonary Wedge Pressure
- Wedge pressure is measured by inserting a catheter through a peripheral vein, passing it through the right side of the heart, pulmonary artery, and into a small branch of the pulmonary artery.
- This measurement, around 5 mm Hg, indicates the pressure in the pulmonary capillaries and is important for capillary fluid exchange functions.
Left Atrial and Pulmonary Venous Pressures
- The mean pressure in the left atrium and major pulmonary veins averages 2 mm Hg in a lying position, ranging from 1 to 5 mm Hg.
- Left atrial pressure is difficult to measure directly, but can be estimated indirectly using pulmonary wedge pressure.
Blood Flow through the Lungs and Distribution
- The volume of blood flow through the lungs is equivalent to cardiac output.
- Pulmonary vascular resistance is controlled by factors affecting cardiac output, such as peripheral factors.
- The lungs maintain a constant blood flow regardless of the body position, but during exercise, the flow is significantly higher in the lower regions of the lungs.
- This is attributed to the effect of gravity on blood flow, ensuring the lower portions of the lungs have a more efficient gas exchange.
Hypoxia and Pulmonary Vasoconstriction
- In cases of local tissue hypoxia, a mechanism called hypoxic pulmonary vasoconstriction helps to maintain efficient blood flow by redirecting blood away from poorly ventilated lung areas and towards well-ventilated areas.
- This vasoconstriction is triggered by local oxygen levels and increased calcium concentration in the smooth muscle cells of the pulmonary arteries and arterioles.
- The effect is to increase pulmonary vascular resistance, redistributing blood flow and minimizing wasted ventilation.
Pleural Fluid Dynamics
- The pleural space, located between the parietal and visceral pleura, contains a thin mucoid fluid to facilitate smooth lung movement.
- The thin layer of fluid facilitates smooth lung movement, preventing friction during breathing.
Pleural Effusion
- Pleural effusion refers to the accumulation of excess free fluid in the pleural cavity.
- Causes include blocked lymphatic drainage, cardiac failure leading to increased capillary pressures, and reduced plasma colloid osmotic pressure.
- The accumulation of fluid in the pleural space can negatively affect lung functioning and requires medical management.
Pulmonary Blood Volume and Distribution
- Approximately 70 ml of pulmonary blood volume is in the pulmonary capillaries
- The remaining pulmonary blood volume is equally distributed between the pulmonary arteries and veins
Lungs as a Blood Reservoir
- The quantity of blood in the lungs can vary from half-normal to twice normal under different physiological and pathological conditions
- For example, blowing air into a trumpet can expel up to 250 ml of blood from the pulmonary circulatory system into the systemic circulation
Pulmonary Capillary Pressure
- The pulmonary capillary pressure is low, typically around 7 mm Hg
- This low pressure helps to prevent fluid leakage into the alveoli
- The importance of low pulmonary capillary pressure is discussed in detail in relation to fluid exchange functions of the pulmonary capillaries
Left Atrial and Pulmonary Venous Pressures
- The mean pressure in the left atrium and major pulmonary veins averages about 2 mm Hg in a recumbent person
- The left atrial pressure can be estimated by measuring the pulmonary wedge pressure
Blood Flow Through the Lungs
- Blood flow through the lungs is equal to cardiac output
- Factors that control cardiac output, found in Chapter 20, also control pulmonary blood flow
Regulation of Pulmonary Blood Flow
- Pulmonary vessels behave as distensible tubes that widen with increased pressure and narrow with decreased pressure
- Local tissue hypoxia causes vasoconstriction in the pulmonary blood capillaries
- This constriction is caused by a decrease in PO2, which triggers a signaling cascade leading to calcium ion influx and vasoconstriction
Pulmonary Edema
- Pulmonary edema occurs when fluid leaks from the pulmonary capillaries into the interstitial spaces and alveoli
- This leakage can be triggered by damage to the pulmonary blood capillary membranes, often due to infections or exposure to noxious substances
- There is a safety factor for pulmonary edema, where the pulmonary capillary pressure must rise to a value at least equal to the colloid osmotic pressure of plasma before significant edema occurs
- The speed of death from acute pulmonary edema depends on how far above the safety factor level the pulmonary capillary pressure rises
Pleural Fluid
- The pleural space is a potential space between the parietal and visceral pleurae
- It is normally very narrow
- Negative pressure in the pleural fluid is required to keep the lungs expanded
- This negative pressure is maintained by lymphatic pumping and helps to prevent lung collapse
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Description
This quiz covers essential concepts in pulmonary physiology, including pulmonary wedge pressure, blood volume in the lungs, and how lungs function as a blood reservoir. Additionally, it explores the regulation of blood flow in response to oxygen levels. Test your understanding of these critical mechanisms in respiratory and circulatory health.
