Respiratory System - Respiratory Organs
Description:
A pair of small, thin walled tubular structure formed by the division of trachea is called primary bronchi. Right bronchus is wider and shorter than left bronchus. Each bronchus undergoes repeated divisions to form secondary and tertiary bronchi. Initial bronchioles are supported by incomplete cartilaginous rings.
Each bronchiole gives rise to a number of structures called alveoli. They are very thin, irregular-walled and vascularized bag-like structure. The alveoli or air sacs serve as the site for respiration.
Lungs
Lungs are composed of bronchi, bronchioles and alveoli.
They are situated in the thoracic chamber.
Human beings have two lungs which are covered by a double layered pleura. Pleural fluid is present in between the two layers.
Outer pleural membrane is in contact with the thoracic lining.
Inner pleural membrane is in contact with the lung surface.
The presence of pleural fluid reduces friction between the two layers and also reduces friction on the lung surface.
Thoracic Chamber
- The thoracic chamber is an air-tight chamber.
- Thoracic chamber is formed dorsally by vertebral column, ventrally by the sternum, laterally by the ribs and lower side by the dome-shaped diaphragm.
- Change in the volume of thoracic cavity will be reflected in the lungs cavity.
Respiratory system has two major parts −
Conducting region − Point starting from external nostrils up to terminal bronchioles. This part transports atmospheric air into the alveoli, clears foreign particles from the air, humidifies and maintains the air temperature similar to that of body temperature.
Respiratory or exchange region − Alveoli and their ducts. This is the site for actual diffusion of oxygen and carbon dioxide between blood and atmospheric air.
The process of respiration involves the following steps −
- Breathing or pulmonary venation by which atmospheric air is drawn in and carbon dioxide rich air is released out.
- Diffusion of gases across the membrane.
- Transport of gas by the blood.
- Diffusion of oxygen and carbon dioxide between blood and tissue.
- Utilisation of oxygen by the cells for catabolic reactions and resultant release of carbon dioxide.