Society and Health: Respiratory Mechanics

These flashcards cover key concepts related to respiratory mechanics, including muscle function, pressure dynamics, and the role of surfactant.

What is the most important muscle involved in inhalation?

The diaphragm.

What is the neural supply to the diaphragm?

Phrenic nerves (C3-C5).

How much does the diaphragm excursion during resting breathing?

Approximately 1 cm.

Describe the role of external intercostal muscles in respiration.

They connect adjacent ribs and, upon contraction, ribs move up and forwards, increasing the chest cavity's dimensions.

What muscles are primarily involved in expiration during quiet breathing?

Expiration is passive due to elastic recoil of lungs and chest wall.

What happens to lung compliance with pulmonary fibrosis?

Compliance is reduced.

What is surfactant, and what is its primary function in the lungs?

A mixture of lipids and proteins that lowers surface tension in the lungs.

What is the effect of interdependence in alveoli during breathing?

Contributes to alveolar stability by preventing collapse of adjacent alveoli.

What determines transpulmonary pressure?

The difference in pressure between inside the lung (Palv) and intrapleural pressure (Pip).

What is the significance of hysteresis in the pressure-volume curve of lungs?

The curve is nonlinear; inflation and deflation curves differ, meaning volume is greater during deflation at the same pressure.

How is airway resistance calculated for laminar flow?

Using Poiseuille’s equation: R = 8ηl/πr^4.

What happens to airway resistance as the radius of airways decreases?

Airway resistance increases significantly.

What is the primary reason for increased work of breathing due to high airway resistance?

A greater pressure gradient is needed to achieve a given airflow rate.

What is the role of surfactant proteins in the lungs?

They help maintain low surface tension and stabilize alveoli.

How does lung volume affect airway resistance?

Lower lung volumes can lead to increased resistance.

What happens to alveolar pressure during expiration?

Alveolar pressure becomes positive.

What factor primarily influences tissue resistance?

Friction between tissues during lung expansion and contraction.

What can occur under conditions lacking surfactant?

The lungs become stiff and areas may collapse.

Describe the effect of pleural pressure during inspiration.

Pleural pressure becomes more negative, allowing lungs to expand.

What is the effect of increased age on lung compliance?

Compliance increases with aging.

What is the pressure in the pleural space relative to atmospheric pressure?

It is always subatmospheric (negative).