Gas Exchange and Perfusion of Lungs
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Questions and Answers

What percentage of air is composed of O2 at sea level?

  • 15%
  • 30%
  • 21% (correct)
  • 24%

    • What is the formula used to calculate Alveolar Ventilation?

  • Tidal Volume + Mechanics of Breathing
  • Tidal Volume - Alveolar Pressure x Breaths per minute
  • Tidal Volume + Anatomic Dead Space x Breaths per minute
  • Tidal Volume - Anatomic Dead Space x Breaths per minute (correct)

    • Why does gas diffusion occur according to partial pressure?

  • Gases remain static until manipulated.
  • Gases move from low to high partial pressure.
  • Gases diffuse from high partial pressure to low. (correct)
  • Gases do not diffuse through epithelial barriers.

    • What is the tidal volume if alveolar ventilation is calculated as 4.2L with an anatomic dead space of 150ml?

    <p>500ml</p> Signup and view all the answers

    What happens to the diffusion of gas at equal partial pressures?

    <p>It completely stops.</p> Signup and view all the answers

    What is the arterial PO2 level after pulmonary venous admixture?

    <p>95 mmHg</p> Signup and view all the answers

    What is the total air pressure at sea level?

    <p>760 mmHg</p> Signup and view all the answers

    Which of the following correctly describes anatomic dead space?

    <p>It is not involved in gas exchange.</p> Signup and view all the answers

    What primarily drives the diffusion of oxygen and carbon dioxide in the lungs?

    <p>Partial pressure of the gases</p> Signup and view all the answers

    Which factor does NOT influence the efficiency of gas diffusion across the alveolar-capillary barrier?

    <p>Blood pH level</p> Signup and view all the answers

    What aspect does NOT impact effective oxygenation and carbon dioxide removal in the lungs?

    <p>Fluid levels in the alveoli</p> Signup and view all the answers

    What must be adequate for sufficient gas exchange at the alveoli?

    <p>Rate of blood flow</p> Signup and view all the answers

    Which of the following represents Dalton's Law in relation to gases?

    <p>The total pressure of a gas mixture equals the sum of individual gas pressures.</p> Signup and view all the answers

    What is the primary concern when assessing ventilation in the respiratory system?

    <p>Whether fresh air reaches the alveoli</p> Signup and view all the answers

    What is a significant factor that can affect the rate of gas transfer across the alveolar membrane?

    <p>Thickness of the membrane</p> Signup and view all the answers

    Which of these is NOT typically measured when assessing lung volumes?

    <p>Rate of breathing</p> Signup and view all the answers

    What happens to systemic arterioles with increased blood flow?

    <p>They can distend more easily.</p> Signup and view all the answers

    Where in the lungs is there typically large blood flow with small air flow?

    <p>Base of the lungs.</p> Signup and view all the answers

    Which condition may cause a decrease in tidal volume?

    <p>Loss of lung elasticity due to fibrosis.</p> Signup and view all the answers

    What is necessary for effective gas exchange at the alveoli?

    <p>Fresh air reaching the alveoli and proper perfusion by blood.</p> Signup and view all the answers

    What best describes the properties of pulmonary circulation?

    <p>Low pressure and high volume system.</p> Signup and view all the answers

    What occurs when blood flow ceases in the alveoli?

    <p>No gas exchange occurs</p> Signup and view all the answers

    What is the typical pressure range in the pulmonary artery?

    <p>25/15 mmHg</p> Signup and view all the answers

    How does the distribution of blood flow in the lungs change with posture?

    <p>More blood flow occurs at the bottom when upright</p> Signup and view all the answers

    What characterizes the pulmonary circulation compared to systemic circulation?

    <p>Pulmonary circulation is a low-pressure system</p> Signup and view all the answers

    What is the primary cause of the low pressure in the pulmonary circulation?

    <p>The configuration of the heart's right ventricle</p> Signup and view all the answers

    Which structure receives blood from the small pulmonary veins?

    <p>Left atrium</p> Signup and view all the answers

    What factor does NOT influence the distribution of blood flow in the lungs?

    <p>Atmospheric pressure</p> Signup and view all the answers

    How does the character of muscular walls in pulmonary arterioles differ from systemic arterioles?

    <p>Pulmonary arterioles have less muscular walls</p> Signup and view all the answers

    What is the primary determinant of minute ventilation in an adult human at rest?

    <p>Tidal volume</p> Signup and view all the answers

    What happens to minute ventilation during hyperventilation?

    <p>It increases</p> Signup and view all the answers

    Which factor primarily influences the central chemoreceptors in respiration regulation?

    <p>Carbon dioxide levels</p> Signup and view all the answers

    What role do peripheral chemoreceptors play in respiratory control?

    <p>Monitor oxygen and hydrogen ions</p> Signup and view all the answers

    How is alveolar ventilation calculated?

    <p>TV - Dead space volume</p> Signup and view all the answers

    In a resting adult, what is the typical tidal volume (TV)?

    <p>0.5 liters</p> Signup and view all the answers

    What occurs during dyspnoea?

    <p>Distressful sensation of breathing</p> Signup and view all the answers

    Which statement about the chemical control of breathing is true?

    <p>PCO2 is the main regulator of breathing.</p> Signup and view all the answers

    Study Notes

    Gas Exchange by Diffusion

    • Diffusion is the movement of gases from areas of high partial pressure to areas of low partial pressure.
    • Partial pressure is the pressure exerted by a gas in a mixture of gases and is proportional to the percentage of the gas in the mixture.
    • Factors influencing the efficiency of diffusion:
      • Partial pressures of gases
      • Thickness of the alveolar-capillary barrier
      • Surface area of the barrier
    • Blood flow is also important for gas exchange.
      • The rate of blood flow through the alveoli determines how much time there is for gas exchange.
      • Perfusion of the alveoli ensures that blood reaches the alveoli for gas exchange.

    Perfusion of Lungs

    • Pulmonary circulation refers to the flow of blood through the lungs.
    • The pulmonary circulation is a low-pressure, high-volume system.
      • It receives the entire cardiac output.
      • Blood pressure in the pulmonary artery is much lower than in the systemic circulation.
    • Blood flow distribution in the lungs is not uniform.
      • Gravity influences blood flow distribution, with more blood flow at the bottom of the lungs in an upright position.
      • The muscular tone of pulmonary arterioles also plays a role, with vasoconstriction decreasing blood flow.

    Ventilation Terminology

    • Dead Space is the volume of air that does not participate in gas exchange.
    • Minute ventilation is the total volume of air breathed in per minute.
      • It is calculated by multiplying tidal volume (TV) by respiratory rate (breaths/minute).
    • Normal minute ventilation in adults at rest is around 6L/minute.
    • Hyperventilation is increased ventilation.
    • Hypoventilation is decreased ventilation.
    • Tachypnoea is an increased rate of respiration.
    • Dyspnoea is a distressful sensation of breathing.

    Alveolar Ventilation

    • Alveolar ventilation is the volume of air that reaches the alveoli per minute.
      • It is calculated by subtracting dead space volume (VD) from tidal volume (TV) and then multiplying by the respiratory rate.
    • Alveolar ventilation is crucial for effective gas exchange.

    Control of Respiration

    • Carbon dioxide (CO2) is the primary regulator of respiration.
      • CO2 levels influence the activity of the respiratory centers in the medulla.
      • CO2 can pass through the blood-brain barrier, while H+ cannot.
    • Hydrogen ion (H+) levels are monitored by peripheral chemoreceptors in the carotid and aortic bodies.
    • Oxygen (O2) levels also influence respiration, but only when arterial PO2 is below 60mmHg.

    CO2 Transport in Blood

    • CO2 is transported in the blood in three forms:
      • Dissolved CO2 (~7%)
      • Carbaminohemoglobin (HbCO2) (~23%)
      • Bicarbonate ions (HCO3-) (~70%)
    • The chloride shift helps maintain electrical neutrality in the blood.

    Chemoreceptors

    • Central chemoreceptors in the medulla respond to changes in CO2 levels.
    • Peripheral chemoreceptors in the carotid and aortic bodies respond to changes in O2 and H+ levels.

    Summary of Gas Exchange & Perfusion

    • Effective gas exchange requires:
      • Adequate ventilation to deliver fresh air to the alveoli
      • Adequate perfusion to bring blood to the alveoli
      • Efficient diffusion across the alveolar-capillary barrier

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    Respiratory Lecture 2 PDF

    Description

    Explore the mechanisms of gas exchange through diffusion and the role of pulmonary circulation. This quiz covers key concepts like partial pressure, factors influencing diffusion efficiency, and the importance of blood flow in the lungs. Test your understanding of how gases are transported and exchanged in the respiratory system.

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