Unit 5.1 - Ventilation: Inhalation and Exhalation

Lungs

Contains branches of airways with air sacs (alveoli) attached at their distal ends.

Each airway divides into 2 airways 23 times.

Conducting Zone

Airways from 0-16.

Absence of alveolus.

Respiratory Zone

Airways 17-23.

Gas exchange occurs between atmospheric air and circulating blood.

2 main types of alveolar cells:

Type I - forms the alveolar walls, single layer, for gas exchange.

Type II - secrete alveolar fluid, secretion surfactant, repair.

Intrapleural Space

Creates an direct artificial linkage between the lungs and the thoracic cage.

A tightly sealed cavity

“Virtual” Pleural Space

Located betweed the parietal and visceral pleura.I

Intrapleural Pressure

Pressure within pleural cavity.

Usually negative but can be positive during force exhalation.

Any change will be reflected in alveolar volume.

Ventilation

By producing a change in lung volume (change in pressure) air can move in and out of the lungs.

Lungs have tendency to collapse (surface tension), balanced with outward elastic recoil of the chest wall; creates intrapleural pressure.

During inhalation, thoracic cavity volume increases → decreases intrapleural pressure → increases lung volume.

Passive (quiet) expiration requires no energy.