Human Body - The Respiratory System

Respiration is a biochemical process where food (glucose) is oxidized to release energy in the form of ATP. The general equation is $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy}$.

Breathing is the physical process of inhaling air rich in $O_2$ and exhaling air rich in $CO_2$.

The human respiratory tract consists of the nostrils, nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, and alveoli.

The trachea or windpipe is held open by 'C' shaped cartilaginous rings to prevent it from collapsing.

Alveoli are tiny balloon-like structures where the actual exchange of gases ($O_2$ and $CO_2$) takes place through the process of diffusion.

The diaphragm is a large, dome-shaped muscular sheet that separates the thoracic cavity from the abdominal cavity.

During inhalation, the diaphragm contracts and moves downwards, and the ribs move upwards and outwards, increasing the volume of the chest cavity and lowering the air pressure inside.

During exhalation, the diaphragm relaxes and moves upwards, and the ribs move downwards and inwards, decreasing the volume and increasing the air pressure to push air out.