Chapter 7 Flashcards
Is inspiration passive or active?
- Active always
Is Expiration Passive or Active?
- Passive during rest
- Active during exercise
What is the most important muscle for inspiration? What is it innervated by?
Muscle
- Diaphragm
Innervation
- Phrenic Nerves that originate from cervical segments 3,4,5
What plays a key role in active expiration?
- contraction of the abdominal muscles
What are the Primary Muscles of Inspiration? What are they innervated by?
- Diaphragm: Phrenic, C3-C5
- Scalenes: C2-C7
What are the Accessory Muscles of Inspiration and Muscles of Expiration? What are they innervated by?
- Sternomastoid: Accessory Nerve & C2-C3
- Intercostal: T1-T11
- Abdominal Muscles (especially Transversus Abdominus): T7-L1
What is the shape of the Pressure-Volume curve of the lung? why is it that shape?
- Linear: because the lung gets stiffer at higher volumes
What is Hysteresis?
the amount of energy/work needed to surpass the airways resistance during inspiration, and expiration.
What is Compliance of the lung?
The slope of Change in Volume/ Change in Pressure
What is responsible for the compliance behaviour of the lung?
- Structural proteins: Collagen and Elastin
- Surface Tension
What can cause a reduction in compliance?
- Pulmonary Fibrosis
- Alveolar Edema
- Increased Venous Pressure
What causes an increase in Compliance?
- Emphysema
- Normal Aging
What balances the tendency of the lung to recoil to its deflated volume?
- The tendency of the chest cage to bow out
What is a similarity about the lungs and the thoracic cage?
- they are both elastic
What is the intra-pleural pressure compared to atomospheric pressure? Why?
Sub-atmoshperic: Because the tendency of the lung to recoil to its deflated volume is balanced by the tendency of the chest cage to bow out
What determines the Pressure-Volume Curve?
- Elastic properties of both the lung and chest wall determine the combined volume
What happens at FRC? (functional reserve capacity)
- The inward pull of the lung is balanced by the outward spring of the chest wall
At what volumes does the Lung retract?
- All volumes above minimal volume
At what volumes does the chest wall expand?
- Volumes up to 75% of vital capacity
What does Pulmonary Surfactant do?
- Reduces the surface tension of the alveolar lining layer
What is Pulmonary Surfactant Produced by?
- Type II alveolar Epithelial cells
What does Pulmonary Surfactant Contain?
- DPPC
What results from the absence of Pulmonary Surfactant?
- Reduced Lung compliance
- Alveolar Atelectasis (complete or partial collapse)
- Pulmonary Edema
What are some regional differences in lung Ventilation?
- Weight of the upright lung causes a higher (less negative) intrapleural pressure around the base compared with apex
- Because pressure-volume curve is non-linear, alveoli at the base expand more than do those at the apex
- If a small inspiration is made from residual volume (RV), the extreme base of the lung is unventilated