The respiratory organs of a man is a lung. Some accessory respiratory organs are
1. Nose
2. Pharynx
3. Trachea.
1. Nose: It’s outermost opening, having a pair of external nares (nostrils) followed by a ridge, the nose. Air enters through nostrils. The nostrils contain hair which helps in filtering out the dirt of air. Other foreign particles i.e. germs may lodge on the moist mucous membrane of the nasal passage. The nasal passage leads internally through the internal nares into the pharynx.
2. Pharynx: From the nasal passage air enters the throat through the pharynx. Pharynx contains the openings of windpipe (trachea) called glottis and of food passage (oesophagus) called gullet. Between these two openings, there is a cartilaginous flap, the epiglottis which normally covers the gullet, except when something is swallowed; when it covers the glottis, so that chewed food only enters in the food pipe.
3. Trachea: The trachea is a pipe like structure, which is as long as the neck of the man. Trachea is covered by a semi-circular ring like cartilage on its sides and front. At its upper part is Larynx, the sound box. In the region of the chest, trachea bifurcates into bronchii. Each bronchus enters into the lung of the same side and there, it further divides into many branches-the bronchioles and fine capillaries each entering into air-sacs.
Main respiratory organ:
Lungs:
Lungs are two in number. These are enclosed in chest box. Each lung has a double wall of pleural membrane. The outer pleural membrane is in contact with muscles of ribs. Each lung is a spongy bag-like structure.
The inner pleural membrane is raised into a large number of sacs, the air sacs which increase the area for exchange of gases. These air sacs, are richly supplied with blood vessels.
Each air sac looks like a cluster of a number of grapes and consists of a number of balloon-like swelling, called alveoli. These alveoli are thin, moist membranes and one cell thick layers. They are in close contact with the extensive capillary network. They act as a functional unit of lungs, in which the exchange of gases takes place.
