Physiology of Respiratory System
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Questions and Answers

What is the primary purpose of the respiratory system?

  • To remove oxygen from the body
  • To provide oxygen and remove carbon dioxide (correct)
  • To facilitate the transport of nutrients
  • To regulate body temperature

    • Which of the following pressures is responsible for expanding the lungs during inhalation?

  • Alveolar pressure
  • Atmospheric pressure
  • Transpulmonary pressure
  • Intra-pleural pressure (correct)

    • What is the term for the movement of air in and out of the lungs?

  • Ventilation (correct)
  • Perfusion
  • Respiration
  • Diffusion

    • Which of the following is NOT a function of the respiratory muscles?

    <p>Regulating body temperature</p> Signup and view all the answers

    What is the term for the exchange of oxygen and carbon dioxide between alveolar air and blood in lung capillaries?

    <p>Diffusion</p> Signup and view all the answers

    What is the effect of 'dead space' on alveolar ventilation?

    <p>It decreases the efficiency of gas exchange</p> Signup and view all the answers

    What is the term for the pressure that inflates the lung?

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

    During inspiration, intrapleural pressure is:

    <p>Negative</p> Signup and view all the answers

    What is the effect of inspiratory muscles contraction on intrapleural pressure?

    <p>Intrapleural pressure decreases</p> Signup and view all the answers

    When does air flow into the lungs?

    <p>When PAlv is lower than PB</p> Signup and view all the answers

    What is the result of high transpulmonary pressure?

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

    What opposes the inward elastic recoil of the lung?

    <p>Negative intrapleural pressure</p> Signup and view all the answers

    What is the primary function of the diaphragm during inspiration?

    <p>Forceful contraction to increase chest cavity volume</p> Signup and view all the answers

    What happens to the intrapleural pressure (Ppl) as the chest cavity expands?

    <p>It falls slightly</p> Signup and view all the answers

    What is the primary purpose of the pleural fluid and membranes?

    <p>To provide cohesion between the lungs and chest cavity</p> Signup and view all the answers

    What happens to the lungs during inspiration?

    <p>They expand to increase volume</p> Signup and view all the answers

    What is the transmural pressure calculated as?

    <p>The pressure inside the compartment minus the pressure outside</p> Signup and view all the answers

    What is the usual value of intrapleural pressure (Ppl) at rest?

    <p>-0.5 KPa (-5 cm H2O)</p> Signup and view all the answers

    What happens to the transpulmonary pressure (PL) as the chest cavity expands?

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

    What is the purpose of recruiting accessory muscles during inspiration?

    <p>To increase the force of contraction</p> Signup and view all the answers

    What is the ratio of anatomical dead space to tidal volume in this example?

    <p>1:5</p> Signup and view all the answers

    What is the total ventilation in this example?

    <p>7500 ml/min</p> Signup and view all the answers

    What is the alveolar ventilation in this example?

    <p>5250 ml/min</p> Signup and view all the answers

    What are the two main sources of resistance that the respiratory muscles must work to overcome?

    <p>Elastic resistance and airway resistance</p> Signup and view all the answers

    What is the result of an increase in elastic resistance and airway resistance in lung diseases?

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

    What is the volume of alveolar gas in this example?

    <p>3000 ml</p> Signup and view all the answers

    What is the frequency of breathing in this example?

    <p>15/min</p> Signup and view all the answers

    What is the primary mechanism by which the chest wall expands to its resting state?

    <p>Outwardly directed elastic recoil of the chest wall</p> Signup and view all the answers

    What is the pulmonary blood flow in this example?

    <p>5000 ml/min</p> Signup and view all the answers

    What is the approximate total lung capacity for a 70 kg young male?

    <p>7300 mL</p> Signup and view all the answers

    What is the formula for calculating minute ventilation?

    <p>Breathing rate (R) x tidal volume (VT)</p> Signup and view all the answers

    What is the approximate value of residual volume for a 70 kg young male?

    <p>1800 mL</p> Signup and view all the answers

    What is the term for the volume of air that does not participate in gas exchange?

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

    What is the approximate value of anatomic dead space in a healthy individual?

    <p>150 mL</p> Signup and view all the answers

    What is the term for the sum of the tidal volume and the inspiratory reserve volume?

    <p>Inspiratory capacity</p> Signup and view all the answers

    What is the value of minute ventilation at rest, given a breathing rate of 15 breaths/min and a tidal volume of 500 mL?

    <p>7500 mL/min</p> Signup and view all the answers

    Study Notes

    Respiratory System Overview

    • The respiratory system provides oxygen (O2) and removes carbon dioxide (CO2) through the process of respiration.

    Steps in Respiration

    • Ventilation: movement of air in and out of the lungs by bulk flow
    • Exchange of O2 and CO2 between alveolar air and blood in lung capillaries by diffusion
    • Transport of O2 and CO2 through pulmonary and systemic circulation by bulk flow
    • Exchange of O2 and CO2 between blood in capillaries and respiring tissues by diffusion

    Respiratory Muscles

    • Diaphragm: contracts during inspiration, relaxes during expiration
    • Intercostals: external and internal intercostal muscles contract during inspiration, relax during expiration
    • Accessory muscles: recruited during forced inspiration

    Lung Mechanics

    • Expansion of the chest cavity causes expansion of the lungs due to the pleural membranes and fluid between them
    • Intrapleural pressure (Ppl) is usually slightly negative, falling during inspiration and rising during expiration
    • Transpulmonary pressure (PL) rises during inspiration, causing expansion of the lungs

    Transmural Pressures

    • Calculated as the pressure differential of the inside compartment minus the outside compartment
    • PAlv: alveolar pressure
    • PPl: intrapleural pressure
    • PB: barometric pressure
    • PL: transpulmonary pressure (the "distending pressure" that inflates the lung)
    • Pw: trans chest wall pressure
    • Prs: trans total system pressure

    Inspiratory Process

    • Intrapleural pressure (PPl) becomes negative during inspiration
    • Alveolar pressure (PAlv) becomes lower than PB during inspiration
    • Transpulmonary pressure (PL) increases during inspiration
    • Inspiratory muscles contract, increasing the dimensions of the thoracic cavity and reducing intrapleural and airway pressure

    Lung Volumes and Capacities

    • Total lung capacity (TLC)
    • Functional residual capacity (FRC)
    • Residual volume (RV)
    • Tidal volume (VT)
    • Inspiratory reserve volume (IRV)
    • Expiratory reserve volume (ERV)
    • Inspiratory capacity (IC)

    Average Volumes and Capacities

    • Average values for a 70 kg young man
    • Female values are lower on average

    Minute Ventilation

    • Total ventilation per minute (VE)
    • Measured in L/min
    • Calculated by breathing rate (R) x tidal volume (VT)

    Dead Space

    • Anatomic dead space: airway volume with no gas exchange, typically 150 ml
    • Physiologic dead space: anatomic dead space plus areas where gas exchange is dysfunctional
    • Dead space ventilation (VD) = anatomic dead space + alveolar dead space

    Dead Space and Alveolar Ventilation

    • Alveolar ventilation (V) = minute ventilation (V) - dead space ventilation (VD)
    • Calculated by (500 x 15) - (150 x 15) = 5250 ml/min

    Summary of Volumes and Flows

    • Total ventilation: 7500 ml/min
    • Anatomic dead space: 150 ml
    • Alveolar ventilation: 5250 ml/min
    • Alveolar gas volume: 3000 ml
    • Pulmonary capillary blood volume: 70 ml
    • Pulmonary blood flow: 5000 ml/min

    Lung Mechanics - Work of Breathing

    • Two main sources of resistance: elastic resistance of the lung and airway resistance
    • Increased resistance in lung diseases increases the work of breathing and leads to symptoms like dyspnea (breathlessness)

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    Description

    Learn about the respiratory system, lung mechanics, and how pressure differences generate airflow in the chest cavity. Explore the relationship between pressure changes and volume changes.

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