In the broadest sense, respiration is the exchange of gases.
There are different types of respiration:
- External Respiration: Exchange of gases between an organism and its environment
- Cellular Respiration or Internal Respiration: the utilization of oxygen and production of carbon-di-oxide.
The essence of respiratory physiology is the regulation of gas exchange to meet the changing demands of the body. Since diffusion paths for respiratory gas exchange are short, a “respiratory system” does not exist in lower animals.
The respiratory system performs both respiratory and non-respiratory functions grouped thus:
- Primary functions – it maintains constant homoestasis: acid-base regulation and lung air.
- Metabolic functions:
It manufactures surfactant for local use.
Production and removal of Prostaglandins.
Removes norepinephrine and serotonin.
- Defense functions:
Prevents small thrombi from reaching the systemic circulation because it acts as a filter.
Prevents foreign bodies from getting into the body by secreting bronchial cilia, and by presence of hair in the nostrils.
- Other functions:
- May be able to buffer blood volume.
May play a role in clotting as a result of the presence of heparin in the large number of mast cells in the lung.
The air pumps (lungs), is devoid of valves and operates by creating subatmospheric pressure. The operation of the system is composed of the following:
- Pulmonary ventilation
- Pulmonary circulation
- Alveolar ventilation
- Diffusing capacity and diffusion of lungs
- Transportation of gases