Question

Why is breathing external respiration?

Answer 1

Breathing is external respiration because:

1. The formal name for gas exchange is external respiration.
2. It encompasses the mass movement of air into and out of the lungs, as well as the diffusion of oxygen and carbon dioxide into the circulation.
3. While pressure changes in the lungs cause bulk airflow from the outside world, the mechanisms for exchanging alveolar gas are more complex.
4. The surface area of the alveolar membrane, partial pressure gradients of the gases, and the combination of perfusion and ventilation are the basic three components of external respiration.

Components of external respiration:

Surface Area:

1. The surface-area-to-volume ratio of alveoli is extremely high, allowing for efficient gas exchange.
2. Alveoli have a dense network of capillaries that provide several gas exchange sites.

Partial Pressure Gradients:

1. Partial pressure gradients (differences in partial pressure) allow oxygen to enter the bloodstream and carbon dioxide to exit.
2. Both of these processes are happening at the same time.

Ventilation:

1. Changes in the volume and pressure of the lungs trigger ventilation.
2. During normal breathing, the diaphragm, and external intercostal muscles contract, and the ribcage rises.
3. Air pressure falls when the volume of the lungs expands, and more air rushes in.
4. Exhalation causes muscles to relax.
5. Air is ejected as the lungs flex and the air pressure rises.