The process of giving out of air rich in carbon dioxide from the body is called exhalation. During exhalation, the diaphragm relaxes, and ribs are pulled due to contraction of rib muscles. As a result the chest cavity decreases, forcing the air [carbon dioxide] out of the lungs.

The taking in of air rich in oxygen into the body is called inhalation, and giving out of air rich in carbon dioxide is called exhalation. One inhalation and one exhalation constitute one breath.

The contraction and relaxation of the diaphragm facilitate inhalation and exhalation during breathing. It is a dome-shaped muscle that is present below the heart and lungs. It separates the abdominal cavity from the thoracic cavity.

The air from the nasal cavity reaches our lungs through windpipe. Lungs are present in the chest cavity or thoracic cavity. This cavity is enclosed by ribs on the sides. Ribs are 12 pairs of curved bones that connect to the vertebral column at the back and sternum in the front forming a cage which is called rib cage.

Different organisms breathe differently through specialized structures. Insects like cockroaches have tiny openings on the sides of their body which helps in breathing. These openings are called spiracles. It is through these openings that oxygen is taken in, and carbon dioxide is given out.

Exchange of oxygen and carbon dioxide takes place from specialized pores which are surrounded by guard cells. These pores present on the surface of leaves are called stomata. It helps in gaseous exchange during the process of photosynthesis, transpiration and respiration.