All of you know about respiratory function of respiratory system but Do you know about non- respiratory functions of respiratory system..? Let’s come with us to know more about non-respiratory functions of respiratory system. First of all, we’ll starts with a basics of lung structure to get better understand further.
Alveolar Lining Epithelium:
Alveolar Lining Epithelium is exceedingly thin, simple squamous type and consists of two types of cells:
- Type 1 cells are primary lining cells.
- Type 2 cells (granular pneumocytes) secret surfactant.
In addition alveolar also contains:
- Pulmonary alveolar macrophages (PAM), actively phagocytic cells.
- Lymphocytes
- Plasma cells: very active cells; form and secret immunoglobulins.
The Respiratory Membrane:
The air in the alveoli is separated from the blood in the pulmonary capillaries by a “wall” called alveolar capillary membrane or respiratory membrane. It has a thickness in the range of 0.3 to 1 um (average 0.5 um). Due to it’s thinners, the gaseous exchange between the alveoli and blood capillaries is completed within fraction of a second.
Pleura:
The lungs are enveloped by ‘pleura’ which has two layers , parietal and visceral.
- Parietal Pleura: It is adherent to the parities that is , inner side of the chest wall and the thoracie side of the diaphragm.
- Visceral Pleura: It is adherent to the underlying viscus that is, the lung itself.
- Potential space between two layers: Pleural cavity filled with serous lubricating fluid called Pleural fluid.
- Pleural fluid: Adhesive: keep Pleural together, synchronized movement.
Hence, the lungs slide easily on the chest wall but resist by being pulled away from it.
The respiratory system is made up of:
- Nose
- Mouth
- Throat (pharynx)
- Voice box (larynx)
- Windpipe (trachea)
- Airways (bronchi)
- Lungs
Primary function of the respiratory system are:
- To bring oxygen into the body and take carbon dioxide (a waste product of energy production) out of the body.
- Through breathing, inhalation and exhalation, the respiratory system facilitates the exchange of gases between the air and the blood and between the blood and the body’s cells. The respiratory system also helps us to smell and create sound.
The following are the five key functions of the respiratory system:
- Remove CO2 from the body.
- Participate in gathering olfactory information.
- Transport gases from lungs to body cells.
- Regulate blood pH .
- Production of CO2 at the cellular level.
Non Respiratory Functions of Respiratory System:
Acid-Base Balance:
In the body, increases in carbon dioxide lead to increases in hydrogen ion concentration (and vice versa) because of the following reaction:
CO2 + H2O = H2CO3= H+ + HCO3–
The respiratory system can therefore participate in acid-base balance by removing CO2 from the body.
Acting as a Reservoir of Blood:
The pulmonary vascular system is a low pressure system, which occupies a large volume of blood. In the hypovolemic state, the pulmonary vessels constrict, releasing the blood into the systemic circulation in order to increase the effective circulating volume.
Filtration of Blood at the Pulmonary Capillaries:
The venous blood entering the right side of the heart is passed through the pulmonary capillaries before reaching the left side of the heart to be distributed throughout the body. While blood flow in pulmonary capillaries, the large particles such as emboli, air bubbles, cell debris and fat globules get trapped in the pulmonary vessels & that’s how it prevents such particles to entering the systemic circulation and obstructing an end artery supplying a vital organ such as the brain.
Removal of Inhaled Foreign Particles and Infectious Organisms:
The nasal mucosa is lined by a ciliated epithelium with the cilia beating towards the pharynx so that the foreign particles can be swallowed. The nasal cavity also have harbors hair covered with mucus which acts like a filter. The upper respiratory tract has a moist surface which is covered by mucus so that large particles get adhered and are therefore prevented from reaching the lower respiratory tract. The nasal cavity is supplied by sensory nerve endings of the trigeminal nerve which are sensitive to irritants. If an irritant is inhaled, the sneezing reflex is activated and the particles are eliminated. And that’s how the removal of inhaled particles & infectious organisms takes place.
Phonation:
It is the production of sounds by the movement of air through the vocal cords. Speech, singing, and other sounds are produced by the actions of the central nervous system controllers on the muscles of respiration, causing air to flow through the vocal cords and the mouth.
Main function of the respiratory system in general and the lung in particular i.e. Gas exchange.
Non respiratory function of Respiratory System includes:
A) Lung Defense Mechanisms:
Functions of Respiratory passage:
- Humidity and cool or warm the inspired air so that even the very hot or very cold air approaches body temperature by the time it reaches the alveoli.
- Bronchial secretions contained secretary immunoglobins ( IgA) that help resist infection and maintain the integrity of the mucosa.
- Prevent foreign body from reaching the alveoli:
- Particles > 10 um diameter: strained out by hairs in the nostrils.
- Particles 2- 10 um diameter: fall on the walls of the bronchi, there they initiate coughing and are moved away from the lungs by the ciliary escalator action.
- Particles <2 um diameter: generally reach the alveoli, where they are ingested by the Pulmonary alveolar macrophages (PAM’s dust cells).
B) Functions of Pulmonary Circulation:
- Reservoir for left ventricle (LV)
- Pulmonary Circulation as a filter. The particle main include blood clots, fat cells, cancer cells and gas bubbles.
- Fluid exchange and Drug Absorption:
- Low pulmonary hydrostatic pressure tends to pull fluid from alveoli into pulmonary capillaries and keeps the alveolar surface free from liquids.
- Drugs that rapidly passes through the alveolar capillary barrier by diffusion, rapidly enter the systematic circulation. Therefore, these are administrated by inhalation e.g. (a) Anaesthetic Gases, (b) Aerosal and other Broncho-dilators.
C) Metabolic and endocrine functions of the lungs:
- Substance synthesized and used in the lungs: surfactant.
- Substances synthesized or stored and released into the blood: Prostaglandins and histamine.
- Substances removed from the blood: many vasoactive substances such as Prostaglandins and Bradykinin are inactive, altered or removed from the blood as they pass through the lungs.
- Substances activated in the lungs ( specially pulmonary circulation) e.g.
Angiotensin I Decapeptide by converting enzyme to Angiotensin II Octapeptide