Ch 7 Mechanics Part 1 Flashcards
What is the primary function of the diaphragm during inspiration?
The diaphragm contracts, increasing the vertical dimension of the chest cavity and aiding in lung expansion.
The diaphragm is supplied by the phrenic nerves from cervical segments 3, 4, and 5.
What occurs during paradoxical movement of the diaphragm?
When one side of the diaphragm is paralyzed, it moves up rather than down during inspiration.
This can be observed using fluoroscopy.
Which muscles are primarily involved in active expiration?
The abdominal muscles, including the rectus abdominis, internal and external oblique muscles, and transversus abdominis.
These muscles raise intra-abdominal pressure and push the diaphragm upward.
What is the pressure-volume curve of the lung?
It is a plot showing the relationship between the pressure around the lung and its volume, demonstrating hysteresis between inflation and deflation.
Hysteresis means the inflation and deflation curves are different.
Define compliance in the context of lung mechanics.
Compliance is the slope of the pressure-volume curve, defined as ΔV/ΔP, indicating the volume change per unit pressure change.
Normal lung compliance is about 200 ml·cm water−1.
What factors can reduce lung compliance?
- Increase of fibrous tissue (pulmonary fibrosis)
- Alveolar edema
- Long periods of unventilated lung
- Increased pulmonary venous pressure
Reduced compliance may also be caused by atelectasis.
What is the role of surfactant in the lungs?
Surfactant lowers the surface tension of the alveolar lining fluid, contributing to lung compliance and stability.
It is primarily composed of phospholipids, particularly dipalmitoyl phosphatidylcholine (DPPC).
True or False: Expiration is always an active process.
False
Expiration is passive during quiet breathing but becomes active during exercise.
What is the main effect of surface tension on lung mechanics?
Surface tension contributes significantly to the static recoil force of the lung and affects compliance.
High surface tension can lead to decreased lung compliance.
Fill in the blank: The pressure inside the airways and alveoli is equal to _______ when the alveolar pressure is atmospheric.
transpulmonary pressure
What happens to airway resistance during forced expiration?
Dynamic compression of airways occurs, increasing resistance.
This can lead to uneven ventilation and decreased airflow.
What are the accessory muscles of inspiration?
- Scalene muscles
- Sternomastoids
- Alae nasi
These muscles are not significantly active during quiet breathing but are engaged during exercise.
What is the primary site of airway resistance in the lung?
The small airways.
Factors like airway closure can affect resistance.
Describe the hysteresis phenomenon in lung inflation and deflation.
The lung volume at any given pressure during deflation is larger than during inflation, indicating different curves for the two processes.
This behavior complicates the interpretation of lung mechanics.
What is the significance of the elastic tissue in the lung?
It contributes to the lung’s elastic recoil and its ability to return to resting volume after distension.
This tissue includes elastin and collagen fibers.
What is the relationship between lung size and compliance?
Larger lungs exhibit greater compliance compared to smaller lungs, leading to different specific compliance values.
This is important for understanding variations across species.
What happens to lung compliance with aging?
Compliance may increase in pulmonary emphysema and with normal aging due to changes in elastic tissue.
This can affect lung function and respiratory health.
What is the role of intercostal muscles during breathing?
They assist in expanding the thoracic cavity during inspiration and aid in active expiration by pulling the ribs downward and inward.
The external intercostals have the opposite action to the internal intercostals.
What is the primary function of surfactant in the alveoli?
Reduces the surface tension of the alveolar lining layer.
Surfactant is crucial for maintaining proper lung function and preventing alveolar collapse.
Which cells produce pulmonary surfactant?
Type II alveolar epithelial cells.
These cells are essential for the synthesis and secretion of surfactant.
What key component is found in pulmonary surfactant?
Dipalmitoyl phosphatidylcholine (DPPC).
DPPC plays a significant role in reducing surface tension.
What are the consequences of surfactant absence?
Reduced lung compliance, alveolar atelectasis, and tendency to pulmonary edema.
These conditions are characteristic of infant respiratory distress syndrome.
How does surfactant affect lung compliance?
Increases compliance and reduces the work of expanding the lung with each breath.
Low surface tension helps the lungs to expand more easily.
What physiological advantage does surfactant provide regarding alveolar stability?
Promotes stability of the alveoli and reduces the tendency for small alveoli to collapse into larger ones.
This counteracts the natural tendency for smaller bubbles to collapse into larger ones due to pressure differences.
What role does surfactant play in keeping the alveoli dry?
Prevents the transudation of fluid from capillaries into the alveoli.
By reducing surface tension forces, surfactant helps maintain proper fluid balance.
True or False: Surfactant increases the surface tension of the alveolar lining layer.
False.
Surfactant significantly decreases surface tension.
Fill in the blank: The pressure generated by a given surface force in a bubble is inversely proportional to its _______.
Radius.
This principle explains why smaller bubbles have higher internal pressures.
What mechanism contributes to the stability of alveoli in the lung?
Interdependence of alveoli.
Surrounding alveoli provide support to one another, helping to maintain structure.
What happens to surface tension when lung washings are introduced into saline?
Surface tension changes greatly with surface area, showing hysteresis and falling to extremely low values when the area is small.
This behavior is crucial for understanding lung function and alveolar stability.
