L1: Pulmonary Vent

What is the respiratory cycle?

-includes inspiration and expiration, which involve changes in pressures in the lungs and pleural space

Why is the pressure in the pleural space negative?

-thoracic cavity is larger than the lungs

-lungs want to collapse while the chest wall wants to expand

→ creating a relative negative pressure in pleural space

How does inspiration affect pressures in the lungs and pleural space?

During inspiration, the diaphragm contracts, increasing thoracic cavity size, making pleural pressure more negative & alveolar pressure negative → allowing air to flow in

-P within lungs is lower than outside so follows the P gradient

How does expiration affect pressures in the lungs and pleural space?

During expiration, pleural pressure becomes less negative, and alveolar pressure becomes positive, driving air out of the lungs

How does alveolar pressure change through a respiratory cycle?

Alveolar pressure is negative during inspiration, positive during expiration, and zero at the end of both inspiration and expiration.

What are lung volumes and capacities?

-tidal V: amt air moved in and out of the lungs during a single breath

-expiratory reserve V: the amt of air that can be forcibly exhaled from the lungs after a normal exhalation

-inspiratory reserve volume: the additional amount of air that can be forcibly inhaled after a normal, quiet breath, starting at the end of a normal inhalation

-residual volume: the amount of air remaining in the lungs after a maximal exhale

-vital capacity: max V of air that can be exhaled from the lungs after a full inhalation

total lung capacity: the maximum amount of air a person can hold in their lungs after a deep, maximal inhalation

What is the most important factor contributing to airway resistance?

Airway radius is the key factor affecting resistance, as smaller radii increase resistance significantly

How do obstructive lung diseases affect airway resistance?

Diseases like equine asthma increase airway resistance due to bronchoconstriction and mucus accumulation, reducing airflow.

What is minute ventilation?

-volume of air ventilated per minute

-calculated (breathing freq x TV)

What is alveolar ventilation?

-V of air reaching the alveoli per minute

-accounts for dead space.

What is compliance?

-ability of the lungs to stretch and expand, influenced by elastic fibers and surfactant.

What is elastance?

Elastance is the reciprocal of compliance, measuring the resistance of the lungs to expand.

What is surface tension in the lungs?

Surface tension is created by the air-water interface in the alveoli, which is reduced by surfactant to prevent alveolar collapse

What is the role of type II pneumocytes and surfactant?

-produce surfactant

• reduces surface tension in the alveoli and prevents collapse during expiration.

What is the work of breathing?

-energy required for tidal ventilation, overcoming elastance and airway resistance.

How do lung disorders affect the work of breathing?

Restrictive disorders increase the pressure needed to inflate lungs, while obstructive disorders increase resistance during expiration, both raising the work of breathing

How does the rate of breathing relate to the total work of breathing?

Animals may increase respiratory rate and decrease tidal volume to reduce effort when breathing becomes difficult.