Mechanics of Pulmonary Ventilation
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Questions and Answers

What is a typical value for the expiratory reserve volume (ERV) in a healthy adult?

  • 500 ml
  • 3.1 L
  • 1.2 L (correct)
  • 70 ml

What is the primary function of alveolar ventilation in the respiratory system?

  • To remove carbon dioxide from the blood
  • To facilitate gas exchange between the alveoli and the blood (correct)
  • To control the rate of breathing
  • To transport oxygenated blood to the tissues

What is the approximate percentage of nitrogen in atmospheric air?

  • 0.03%
  • 3.6%
  • 79% (correct)
  • 20%

Which of the following accurately describes the relationship between vital capacity (VC) and total lung capacity (TLC)?

<p>VC is smaller than TLC (A)</p> Signup and view all the answers

What is the volume of air remaining in the lungs after a maximal expiration?

<p>Residual volume (RV) (C)</p> Signup and view all the answers

What is the total volume of air that can be forcibly exhaled after a maximal inspiration?

<p>Vital capacity (VC) (D)</p> Signup and view all the answers

What is the volume of air remaining in the lungs at the end of a normal expiration?

<p>Functional residual capacity (FRC) (C)</p> Signup and view all the answers

If a healthy adult takes one normal breath (tidal volume), how much of that air actually reaches the alveoli to participate in gas exchange?

<p>350 ml (D)</p> Signup and view all the answers

What is the primary function of the respiratory system?

<p>To supply the body with oxygen and remove carbon dioxide (D)</p> Signup and view all the answers

During normal quiet respiration, what is the main muscle that drives ventilation?

<p>The diaphragm (C)</p> Signup and view all the answers

According to Boyle's law, what relationship exists between the pressure and volume of a gas in a closed container?

<p>An inverse relationship where as volume increases, pressure decreases (D)</p> Signup and view all the answers

What nerve innervates the diaphragm, enabling its contraction?

<p>The phrenic nerve (A)</p> Signup and view all the answers

Which muscles are involved in elevating the ribs during deep, forceful inspiration?

<p>The external intercostals, the sternocleidomastoids, the scalene muscles, and the Pectoralis minor (A)</p> Signup and view all the answers

The expansion of the thoracic cavity during inhalation results in which of the following?

<p>A decrease in intrapleural pressure (D)</p> Signup and view all the answers

What is the source of carbon dioxide that needs to be removed from the body?

<p>Krebs cycle (C)</p> Signup and view all the answers

What is the pressure inside the alveoli relative to atmospheric pressure required for air to flow into the lungs?

<p>Pressure inside the alveoli must be lower (A)</p> Signup and view all the answers

What primarily drives normal expiration during quiet breathing?

<p>Elastic recoil of the chest wall and lungs (D)</p> Signup and view all the answers

What is tidal volume in the context of respiration?

<p>Volume of air exchanged in one breath (A)</p> Signup and view all the answers

What percentage of tidal volume is available for gas exchange in healthy individuals?

<p>70% (D)</p> Signup and view all the answers

What happens during forceful expiration?

<p>Muscle contractions increase abdominal and thoracic pressure (C)</p> Signup and view all the answers

Which structure serves as the anatomic dead space in the respiratory system?

<p>Conducting airways (C)</p> Signup and view all the answers

Flashcards

Quiet Expiration

Expiration during quiet breathing is a passive process driven by the elastic recoil of the chest wall and lungs, not active muscle contraction.

Tidal Volume

The volume of air that is breathed in and out in one normal breath.

Anatomic Dead Space

The volume of air within the conducting airways like the nose, trachea, and bronchi that does not participate in gas exchange.

Expiration (Active)

The process of air moving out of the lungs against a pressure gradient, similar to inspiration but with reversed pressure.

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Alveolar Pressure during Expiration

When the pressure inside the alveoli is greater than atmospheric pressure, causing air to move out of the lungs.

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Pulmonary Ventilation

The process of moving air into and out of the lungs.

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Alveolar Ventilation

The volume of air that actually reaches the alveoli in the lungs.

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External Respiration

The exchange of gasses between the alveoli and the blood stream.

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Internal Respiration

The exchange of gasses between the blood and the tissues.

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Vital Capacity (VC)

The maximum volume of air that can be forcibly exhaled after a maximal inspiration.

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Breathing

The process of gas exchange between the atmosphere and the alveoli, involving the alternate contraction and relaxation of respiratory muscles to generate a pressure difference that drives air flow.

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Functional Residual Capacity (FRC)

The volume of air that remains in the lungs after a normal expiration.

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Inspiration

The movement of air into the lungs. It occurs when the pressure inside the alveoli is lower than atmospheric pressure.

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Expiration

The movement of air out of the lungs. It occurs when the pressure inside the alveoli is higher than atmospheric pressure.

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Residual Volume (RV)

The volume of air that remains in the lungs after a maximal expiration.

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Total Lung Capacity (TLC)

The total volume of air that the lungs can hold.

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Intralveolar pressure

The pressure inside the alveoli must be lower than atmospheric pressure for air to enter the lungs.

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Boyle's Law

Boyle's law states that as the volume of a gas increases, its pressure decreases, and vice versa. This principle applies to lung expansion during breathing.

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Diaphragm

The main muscle of inspiration, which flattens upon contraction, increasing the vertical dimensions of the thoracic cavity and lowering the pressure inside the alveoli.

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Pleural Space

The thin space between the visceral and parietal pleura, containing a subatmospheric pressure that helps to expand the lungs during inspiration.

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Pleural Adherence

The two layers of the pleura are adhered due to the subatmospheric pressure in the pleural space, and the surface tension between the layers. This adherence allows for efficient lung expansion.

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Study Notes

Mechanics of Pulmonary Ventilation

  • The body needs oxygen to support cellular respiration, specifically the electron transport system.
  • The Krebs cycle produces carbon dioxide.
  • Ventilation is gas exchange between the atmosphere and the alveoli.
  • Respiratory muscles generate a pressure difference to drive airflow. Inspiration is breathing in, expiration is breathing out.

Inspiration

  • For air to enter, the pressure inside the alveoli must be lower than atmospheric pressure.
  • Intraalveolar pressure is lowered by increasing lung volume.
  • Boyle's law states an inverse relationship between pressure and volume in a closed container.

Boyle's Law

  • Decreasing volume increases collisions, increasing pressure. A specific example is provided:
    • Initial volume (V₁) = 1.0 L, pressure (P₁) = 100 mmHg
    • Final volume (V₂) = 0.5 L, pressure (P₂) = 200 mmHg

Inspiration (Process)

  • Increasing lung volume by lung expansion lowers pressure below 1 atm.
  • The diaphragm, innervated by the phrenic nerve (C3/4/5), is the primary muscle responsible.
  • Contraction flattens the diaphragm, increasing the vertical dimensions of the thoracic cavity.
  • This process, in conjunction with other muscles (e.g. external intercostals, sternocleidomastoids, scalenes, pectoralis minor) further expands the thoracic cavity and results in lower intra-alveolar pressure.
  • Air flows in.

Inspiration (steps outlined)

  • Diaphragm relaxes.
  • Diaphragm contacts increasing thoracic volume.
  • Diaphragm relaxes decreasing thoracic volume.

Inspiration (additional details)

  • Increased size of the thoracic cavity lowers the pressure inside the alveoli to below 1 atm.
  • This allows air to flow from the atmosphere into the alveoli based on a high-low pressure gradient.
  • The diaphragm is the primary muscle in quiet breathing. Other muscles are involved in forceful breathing. The external intercostals, sternocleidomastoids, and scalenes all raise the ribs, assisting in expanding the thoracic cavity.

Expiration

  • Normal quiet expiration is a passive process driven by the elastic recoil of the chest wall and lungs.
  • Pressure inside the alveoli is greater than atmospheric pressure.
  • The process is similar to inspiration, but with a reversed pressure gradient.
  • In forceful expiration, other muscles contract:
    • The abdominal wall musculature and the internal intercostals are involved.
    • These increase abdominal and thoracic pressure, pushing the diaphragm upwards and pulling the ribs inwards.

Pulmonary and Alveolar Ventilation

  • Pulmonary ventilation = tidal volume (500 ml).
  • Approximately 150 ml of air does not reach the alveoli.
  • Alveolar ventilation refers to the remaining air (350 ml) that reaches the alveoli.
  • The composition of the air we breathe (including nitrogen and oxygen) is shown in a table.

Lung Volumes and Capacities

  • Various lung volumes and capacities are defined and illustrated.
  • Key volumes include inspiratory reserve volume (IRV), expiratory reserve volume (ERV), tidal volume (TV), residual volume (RV).
  • Key capacities include inspiratory capacity, functional residual capacity, vital capacity, and total lung capacity (TLC), and their respective formulas.

Lung volumes (additional details)

  • Inspiratory reserve volume (IRV) is the additional air that can be forcibly inhaled after a normal inspiration.
  • Expiratory reserve volume (ERV) is the additional air that can be forcibly exhaled after a normal expiration.
  • Vital capacity (VC) is the maximum volume of air that can be forcibly exhaled after a maximal inspiration (VC = TV + IRV + ERV).
  • Residual volume (RV) is the volume of air remaining in the lungs after a maximal forced expiration.
  • Functional residual capacity (FRC) is the volume of air remaining in the lungs at the end of a normal expiration (FRC = RV + ERV).
  • Total lung capacity (TLC) is the volume of air in the lungs at the end of a maximal inspiration (TLC = FRC + IRV).

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Description

Test your knowledge on the mechanisms of pulmonary ventilation, including concepts like inspiration, expiration, and Boyle's law. This quiz covers the role of respiratory muscles and the pressure changes involved in gas exchange. Understand how air moves in and out of the lungs through these principles.

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