Anatomy and Physiology of Respiratory System
Physiology of Respiration
The respiratory primarily supplies oxygen to the body and disposes of carbon dioxide through exhalation. Four events chronologically occur, for respiration to take place.
- Pulmonary ventilation – this process is commonly termed as breathing. With pulmonary ventilation, air must move out into and out of the lungs so that the alveoli of the lungs are continuously drained and filled with air.
- External respiration – this is the exchange of gases or the loading of oxygen and the unloading of carbon dioxide between the pulmonary blood and alveoli.
- Respiratory gas transport – this is the process where the oxygen and carbon dioxide is transported to the and from the lungs and tissue cells of the body through the bloodstream.
- Internal respiration – in internal respiration the exchange of gases is taking place between the blood and tissue cells.
Mechanics of Breathing
Breathing, also called pulmonary ventilation is a mechanical process that completely depends on the volume changes occurring in the thoracic cavity. Thus, a when volume changes pressure also changes, and this would lead to the flow of gases equalizing with the pressure.
Inspiration – also called inhalation. This is the act of allowing air to enter the body. Air is flowing into the lungs with this process. Inspiratory muscles are involved with inspiration which includes:
- The diaphragm
- External intercostals
These muscles contract when air is flowing in and thoracic cavity increases. When the diaphragm contracts it slides inferiorly and is depressed. As a result the thoracic cavity increases. The contraction of the external intercostal muscles lifts the rib cage and thrusts the sternum forward. This increases the anteroposterior and lateral dimensions of the thorax.
Expiration – also called expiration. It the process of breathing out air as it leaves the lungs. This process causes the gases to flow out to equalize the pressure inside and outside the lungs. Under normal circumstances, the process of expiration is effortless.