In: Anatomy and Physiology
While working the night shift in the ER, you see a patient who has sustained a collapsed lung. The patient is struggling to breath. Which muscles would you see the patient using to inhale?
a. The accessory muscles for inhalation are the scalenes and abdominal muscles.
b. The accessory muscles for inhalation are the internal intercostals, scalenes, and pectoralis minor.
c. The accessory muscles for inhalation are the external intercostals, sternocleidomastoid, scalenes, and pectoralis minor.
d. The accessory muscles for inhalation are the internal intercostals and abdominal muscles.
CORRECT ANSWER: c. The accessory muscles for inhalation are the external intercostals, sternocleidomastoid, scalenes and pectoralis minor
EXPLANATION:
Inspiration is an active process in which air enters into the lungs by the contraction of diaphragm and external intercostal muscles. Diaphragm flattens and external intercostal muscles increases the antero- posterior dimension of thoracic cavity so that air enters into the lungs. This is normal quiet inspiration.
Forced inhalation or inspiration:
Forced inhalation takes place whenever there is difficulty in breathing. During this breathing accessory muscles of inhalation are activated. These muscle include external intercostal muscles, sternocleidomastoid, scalenes and pectoralis minor. Sternocleidomastoid elevates the sternum and scalenes elevates the ribs to increase the lung volume of thoracic cavity. This muscles contract simultaneously to produce forced inhalation or active inspiration.