Page 134 - PPL-engelsk 2025

Human Performance

Amphibians, such as frogs, have primitive lungs but can also absorb oxygen

through their skin.

Reptiles, birds, and mammals (including humans) cannot absorb oxygen

through their skin but have highly specialized lungs.

2.3.1 The lungs

The figure below

illustrates the structure

of the lungs.

Air enters the lungs

through the nose and

mouth, passing through
the throat and trachea.

The trachea is stiff due to cartilage rings, which keep the airway open. These

rings can be felt at the front of the neck.

The trachea divides into two main branches, called primary bronchi, leading to
each lung. These bronchi further divide into smaller bronchi, which branch out

into even smaller tubes called bronchioles.

2.3.1.1 Alveoli

At the ends of the bronchioles are small sacs called alveoli. This is where oxygen

is absorbed, and carbon dioxide is released.

The alveolis are in close contact with pulmonary capillaries, meaning the

distance between air in the alveoli and blood in the capillaries is very short—
approximately 0.2 μm.

Capillaries form a network around the alveoli. This close contact ensures that

hemoglobin in the blood can easily absorb oxygen and release carbon dioxide.

Flight Theory PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 134