The respiratory system are responsible for taking in oxygen and using that oxygen the food is broken down to release energy and the waste material CO2 formed is eliminated out of the body and this process is called respiration.
The respiratory system consists of the following parts:
Nostrils :The nostrils are the openings of the nasal cavities and leads into the nasal cavity. The air gets warmed and moistened in this chamber.
Pharynx: The pharynx is a short vertical tube about 12 cm long. It leads in to two tubes, the one at the front is the wind pipe or trachea, and the one at the back is the food pipe or esophagus
Larynx: The larynx is often called the Adam's apple. The vocal cords in the larynx vibrate to produce sounds. Larynx opens in to the laryngopharynx by a slit like aperture, the glottis. It always remains open except during swallowing. The glottis bears a leaf like cartilaginous flap called the epiglottis at its anterior margin.
Trachea: It is a thin walled hollow tube. It is also called the wind pipe. it divides in to right and left primary bronchi. They are supported by cartilaginous rings to prevent collapsing when there is less air in it.
One major bronchus enters the right lung and the other the left lung. The primary bronchus divides in to secondary bronchus and secondary into tertiary bronchii.Tertiary bronchi which divide in to still smaller bronchioles. The small terminal bronchioles give off respiratory bronchioles which divide in to alveolar ducts. The alveolar ducts enter the alveolar sacs. The lungs are housed on either side the hearts in the pleural cavity of the thoracic cavity .They are protected by pleural membranes.
The walls of the air sacs are elastic and are supplied with capillaries from the pulmonary artery. Through these thin walls, air is exchanged between the capillaries and the air sacs.