What Changes Occur In Inter-costal Muscles And Diaphragm During Inspiration And Expiration?

6 Answers

Anonymous Profile
Anonymous answered
1) Expansion of the intrapleural space and an increase in negative pressure
2) This negative pressure generates airflow because of the pressure difference between the atmosphere and alveolus
3) Air enters, inflating the lung through either the nose or the mouth into the pharynx (throat) and trachea before entering the alveoli
4) Chest expand and diaphragm flattened


1) Pressure difference in lung and atmosphere which is pressure is higher in lung, cause air to move out of bronchioles, to airways and outside
2) Chest become smaller and diaphragm in dome shape.

The cycles repeat.
patrick mc mullan Profile
During inspiration the intercostal muscles assist the rib cage in expanding while the diaphragm lowers. On exhalation the diaphragm relaxes to allow it to return to its resting position.Paralysis of the muscles of respiration would lead to death.
Shumaela Rana Profile
Shumaela Rana answered
The act of inhaling is inspiration and the act of exhaling is known as expiration. Breathing is spread over two phases; inspiration and expiration. During inspiration, the dome shaped diaphragm contracts flattening somewhat and thereby lowering the floor of the thoracic cavity. The external intercostal muscles contract raising the rib cage. A combined action of these two events expands the thoracic cavity, which in turn expands the lungs.

As a result of it the air pressure with in the lungs increases. Thus air from the environment outside of the body is pulled into the lungs to equalize the pressure of both sides. In expiration the external intercostal muscles relax and the internal intercostal muscles contract as a result of which ribcage drops. The diaphragm relaxes and assumes dome like shape. The combined action of these two events reduces the volume of the thoracic cavity.

The volume of lungs in turn decreases which results in an increase in the air pressure in the lungs. The air is thus forced out of the lungs. At the lungs, carbon dioxide within the blood of capillaries surrounding the alveoli and oxygen on the air of the alveoli are exchanged. The exchange of gases works by the process of diffusion.

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