Lung Compliance and Intrapleural Pressure Quiz

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Questions and Answers

What is the relationship between intrapleural pressure and intra-alveolar pressure during normal respiratory function?

Intrapleural pressure is equal to intra-alveolar pressure at all times.

Intrapleural pressure is only less than intra-alveolar pressure during expiration.

Intrapleural pressure is always greater than intra-alveolar pressure.

Intrapleural pressure is always less than intra-alveolar pressure. (correct)

What condition occurs if intrapleural pressure equilibrates with atmospheric pressure?

Pulmonary edema

Emphysema

Pneumothorax (correct)

Atelectasis

Which of the following factors decreases lung compliance?

Lower lung volumes

Advancing age

Decreased surface tension at low lung volumes

Deficiency of surfactant (correct)

What defines lung compliance?

The change in lung volume for a given change in pressure. Signup and view all the answers

Which statement correctly describes the deflation limb of lung compliance?

It shows a lower compliance compared to the inflation limb. Signup and view all the answers

In which condition would lung compliance be expected to increase?

Low lung volumes Signup and view all the answers

What underlies the difference in compliance between the deflation and inflation limbs of the pressure-volume curve?

Surface tension is higher during inflation. Signup and view all the answers

What generally happens to lung compliance with advancing age?

It increases due to elastic tissue degeneration. Signup and view all the answers

What is the primary determinant of airway resistance in healthy individuals?

Airway radius Signup and view all the answers

What role does the sympathetic nervous system (SNS) play in airway resistance?

It relaxes bronchiole smooth muscle. Signup and view all the answers

Which factor primarily increases airway resistance in obstructive pulmonary diseases?

Thickening of airway walls Signup and view all the answers

What effect does lung volume have on airway resistance?

Increased lung volume can reduce airway resistance. Signup and view all the answers

Which of the following statements about alveoli is true regarding their tendency to collapse?

Interdependence of alveoli prevents collapse. Signup and view all the answers

What is the relationship between collapsing pressure and alveolar radius?

Inversely proportional Signup and view all the answers

Which factor contributes to decreasing the work of breathing in alveoli?

Alveolar surfactant Signup and view all the answers

What is the main composition of alveolar surfactant?

Phospholipids, lipids, and proteins Signup and view all the answers

Which alveolus has a better surface area to volume ratio for gas exchange?

Small alveolus Signup and view all the answers

How does increasing surfactant concentration affect surface tension in alveoli?

Decreases surface tension Signup and view all the answers

What maintains the interdependence of alveoli?

Adjacent alveoli supporting each other Signup and view all the answers

What complication may occur in premature infants due to surfactant deficiency?

Impaired gas exchange Signup and view all the answers

Which of the following factors is NOT a function of alveolar surfactant?

Increases work of breathing Signup and view all the answers

What effect does surface tension have on collapsing pressure in alveoli?

Inversely related Signup and view all the answers

What is the formula that represents the collapsing pressure in an alveolus?

P = 2T/r Signup and view all the answers

What is the relationship between lung size and thoracic cavity size during normal lung function?

Lung size is less than thoracic cavity size. Signup and view all the answers

What favors lung collapse according to the mechanics of breathing?

Elastic recoil from collagen and elastic fibers in the lung. Signup and view all the answers

What is the intrapleural pressure typically compared to atmospheric pressure?

It is less than atmospheric pressure. Signup and view all the answers

What happens to lung volume during inspiration?

It increases as intra-alveolar pressure drops below atmospheric pressure. Signup and view all the answers

In relation to the thoracic wall, what effect do elastic forces have?

They favor thorax expansion. Signup and view all the answers

What does the transmural pressure gradient represent?

It is the pressure difference responsible for lung expansion during thorax expansion. Signup and view all the answers

What is the outcome at the end of expiration?

Intra-alveolar pressure is equal to atmospheric pressure. Signup and view all the answers

What role do collagen and elastic fibers play in the lungs?

They provide structural integrity against collapse. Signup and view all the answers

During expiration, which of the following is true about intra-alveolar pressure?

It exceeds atmospheric pressure. Signup and view all the answers

What can be measured by a spirometer?

Inspiratory reserve volume (IRV) Signup and view all the answers

What is the total lung capacity (TLC) composed of?

Inspiratory reserve volume + Tidal volume + Expiratory reserve volume + Residual volume Signup and view all the answers

Which of the following is NOT a lung capacity?

Inspiratory reserve volume Signup and view all the answers

Which muscles are primarily involved in inspiration?

Diaphragm and external intercostal muscles Signup and view all the answers

What describes the relationship between lung compliance and lung volume?

Higher compliance allows for easy inflation Signup and view all the answers

What is the primary effect of surface tension in the alveoli?

Increases the work of breathing Signup and view all the answers

What occurs during a pneumothorax?

Air enters the pleural cavity, causing lung collapse Signup and view all the answers

What distinguishes obstructive lung diseases from restrictive lung diseases?

Obstructive diseases decrease airflow while restrictive diseases restrict lung volume Signup and view all the answers

Which factor is likely to increase airway resistance?

Swelling or mucus in the airways Signup and view all the answers

What does the term 'residual volume' refer to?

Air remaining in the lungs after maximum exhalation Signup and view all the answers

Study Notes

Intrapleural Pressure

Intrapleural pressure is always less than intra-alveolar pressure.
This causes the lung to be stretched, even during expiration.
If intrapleural pressure equilibrates with atmospheric pressure, a pneumothorax occurs.

Lung Compliance

Lung compliance refers to a change in lung volume for a given pressure change.
High compliance means the lung is easy to expand.
Factors decreasing lung compliance include a deficiency of surfactant, high lung volumes, and pulmonary congestion.
Factors increasing lung compliance include lower lung volumes and advancing age.
The deflation limb differs from the inflation limb because surface tension is higher during inflation than deflation.

Lung Volumes and Compliance

Lung compliance is increased at low lung volumes and decreased at high lung volumes
This relationship can be visualized on a pressure-volume curve: the slope of the curve represents compliance.

Lung Compliance and Lung Disease

Pulmonary disorders are divided into obstructive and restrictive diseases.
Restrictive diseases involve increased fibrous tissue, reducing lung compliance.
An example of a restrictive disease is pulmonary fibrosis, sometimes caused by asbestos exposure.

Mechanics of Breathing

The elastic forces of the thoracic wall favor thorax expansion, while the elastic forces of the lungs favor lung collapse.
The difference in pressure between the alveoli and the pleural cavity, called the transmural pressure gradient, causes the lungs to expand when the thorax expands.
The breathing cycle at rest involves inspiration and expiration.

Lung Volumes

Lung volumes are measured by a spirometer.
Tidal volume (VT) is the volume of air inhaled or exhaled during normal breathing (~ 500 ml)
Inspiratory reserve volume (IRV) is the extra volume of air that can be inhaled after a normal inspiration (~ 3000 ml)
Expiratory reserve volume (ERV) is the extra volume of air that can be exhaled after a normal exhalation (~1200 ml)
Residual volume (RV) is the air remaining in the lungs after a maximal exhalation (~1200 ml)
RV cannot be measured by spirometry because it cannot be exhaled.

Lung Capacities

Lung capacities are combinations of two or more lung volumes.
Total lung capacity (TLC) is the maximum volume of air the lungs can hold.
Vital capacity (VC) is the maximum volume of air that can be exhaled after a maximal inhalation.
Functional residual capacity (FRC) is the volume of air remaining in the lungs after a normal passive expiration; it is the resting volume of the lung.

Alveolar Stability

The collapsing pressure on an alveolus is directly related to surface tension and inversely related to alveolar radius.
A smaller alveolus has higher collapsing pressure than a large alveolus.
A small alveolus has a better surface area to volume ratio for gas exchange.

Alveolar Surfactant

Alveolar surfactant is a complex mixture of phospholipids, lipids, and proteins produced by type II alveolar epithelial cells.
It reduces surface tension in alveoli, reducing the work of breathing and increasing compliance.
It can be deficient in premature infants.

Interdependence of Alveoli

Adjacent alveoli support each other.
If one alveolus starts to collapse, it pulls on surrounding alveoli, which recoil and pull the collapsing alveolus open.

Airway Resistance

Airway resistance is determined by the Poiseuille equation, which states that resistance is inversely proportional to the fourth power of the radius.
The primary determinant of airway resistance is the radius.
In healthy individuals, the radius is large enough to keep resistance low.

Factors Affecting Airway Resistance

The autonomic nervous system (ANS) influences airway radius.
The parasympathetic nervous system constricts bronchial smooth muscle, while the sympathetic nervous system relaxes it.
Lung volume also influences airway resistance: airway resistance is lower at higher lung volumes.

Airway Resistance in Pulmonary Disease

Obstructive lung diseases, such as asthma, chronic bronchitis, and emphysema, increase airway resistance due to:
- Thickening of airway walls
- Excessive secretions in the airway lumen

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Description

Test your knowledge on intrapleural pressure and lung compliance. Explore factors that influence lung volumes and the implications for lung diseases. Understand how these concepts relate to pressure-volume relationships in the respiratory system.