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How does the mammalian diaphragm help with breathing?
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Vertebrate
The major groups of vertebrates include fishes, amphibians, reptiles, birds, and mammals.
The diaphragm is a dome-shaped, muscular structure that serves as the primary muscle of respiration in mammals, separating the thoracic and abdominal cavities.1
It facilitates breathing through the following mechanics:
- Inspiration: When the diaphragm contracts, it increases the internal height of the thoracic cavity. This action lowers the internal pressure within the chest, which causes air to be drawn into the lungs. During this process, muscle contraction works alongside the outward elastic force of the chest to stretch the lungs.12
- Expiration: During ordinary breathing, expiration is a passive process. It occurs when the diaphragm relaxes, allowing the natural elasticity of the lung tissue and the thoracic cage to return the system to its equilibrium position, thereby expelling air.12
- Forceful Expiration: The diaphragm can also assist in more active or forceful expiration when the abdominal muscles contract, which increases abdominal pressure and pushes the diaphragm upward.2