The respiratory system
provides the body with a constant supply of oxygen from the air. As
we inhale and exhale, fresh air and stale air is drawn in and
expelled respectively from the lungs. Oxygen is taken in and carbon
dioxide is thrown out from the lungs.
The respiratory system consists of:
- Nose and Mouth
- Takes the air in while cleaning it of dust and bacteria.
- Pharynx
- Connects the nose and mouth to trachea.
- Larynx
- Makes the sounds of speech as passing air vibrates the vocal cords.
- Trachea
- Trachea is the wind-pipe.
- It divides into right and left main bronchi, one of which enters each lung.
- Lungs
- There are two of them; right and left. The right lung has three lobes and the left has two lobes. Inside the lungs the bronchi branch again and again to become smaller and smaller, ultimately to reach the size of a hair. These terminal bronchioles end at bubble shaped alveoli. Each of this alveoli are surrounded by capillaries. Exchange of air takes place at this stage.
There are 300 million alveoli in each lung.
Did you know?----
Air we inhale contains 21% oxygen whereas the air we exhale has only 16%.
Did you know?----
We breath in and out about 20,000 times each day.
Did you know?----
Alveoli have an internal surface area of 70sq. meters.
Did you know?----
Alveoli's internal surface area is about 35 times the surface area of the skin covering the body.
During inhalation, the lungs expand pushing the diaphragm down, and during exhalation, they contract. The breathing is controlled by the brain's inspiratory center. The impulse send by the center makes the intercostal muscles and the diaphragm to contract. Once the thorax expands, the inspiratory center stops to act, leading to the relaxation of the muscles and hence, exhalation takes place. The normal breathing rate can vary between 12 and 18 per minute, but any exertion, the breathing rate increases.