Inhalation (also known as inspiration) is the movement of air from the external environment, through the air ways, and into the alveoli.

Inhalation begins with the onset of contraction of the diaphragm, which results in expansion of the intrapleural space and an increase in negative pressure according to Boyle's Law. These negative pressure generates airflow because of the pressure difference between the atmosphere and alveolus. Air enters, inflating the lung through either the nose or the mouth into the pharynx (throat) and trachea before entering the alveoli.

Other muscles that can be involved in inhalation include^[1]:

• External intercostal muscles
• Scalene muscles
• Sternocleidomastoid muscle
• Trapezius muscle

[edit] Hyperaeration

Lungs and breathing activity Commonly confused terminology view • talk • edit

Dyspnea - Shortness of breath

Hyperventilation - increased breathing that causes CO2 loss

Hyperpnea - faster and/or deeper breathing

Tachypnea - increased breathing rate

Hyperaeration/Hyperinflation - increased lung volume

Hyperaeration or hyperinflation is where the lung volume is abnormally increased, with increased filling of the alveoli. This results in an increased radiolucency on X-ray, a reduction in lung markings and depression of the diaphragm. It may occur in partial obstruction of a large airway, as in e.g. congenital lobar emphysema, bronchial atresia and mucous plugs in asthma.^[2]

It causes one form of overexpansion of the lung. Overexpansion, however, can also be caused by increase in lung mass itself.

[edit] See also

Look up inhalation or sniffing in Wiktionary, the free dictionary.

• Inhalant - Psychoactive drugs consumed through inhalation
• Respiratory system
• Ventilation (physiology)
• Exhalation

[edit] References

1. ^ Physiology at MCG 4/4ch2/s4ch2_10
2. ^ Hyperinflation medcyclopaedia.com --> Hyperinflation] Retrieved on June 5, 2009

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