Physiology Learning objectives:
1. State the functions of respiration.
2. Identify the components of the respiratory membrane.
3. Define the laws that govern the movement of gas through a tissue.
4. Distinguish between external and internal respiration.
5. Explain the factors that influence the binding of oxygen to hemoglobin.
6. Compare the transport of carbon dioxide by the blood with that of oxygen.
7. Explain the control of respiration and the factors that influence the rate of
respiration.
Introduction:
Active cells require a constant supply of oxygen in order to produce energy to carry
out cellular processes and release carbon dioxide as a waste product. The body
must replenish this supply of oxygen and remove the build-up of carbon dioxide, as
it is toxic to cells in high concentrations.
The respiratory membrane provides a large surface area and a thin, permeable, and
moist surface where the gaseous exchange of oxygen and carbon dioxide can take
place. At this site, carbon dioxide is released from the blood into the alveoli and out
of the body with each exhalation. Oxygen is obtained from air in the alveoli with
each inhalation and diffuses into the blood, where it is carried to cells of the body.
The respiratory membrane is composed of the cells that form the alveolar wall and
those that form the capillary wall. It forms a barrier between the air in the lungs
and the blood in the capillaries. The membrane is very thin, measuring only 0.5 μm
across, to facilitate the rapid diffusion of oxygen and carbon dioxide across it.
Our respiratory rate, or the number of breaths we take per minute, and the depth at
which we respire with each breath is controlled by the respiratory center, located in
the brainstem.
, It ensures that our respiratory effort matches the metabolic demands of our body.