Can anyone confirm if the diaphram is smooth muscle?

[historian3x]

I was flipping through my A&P book, couldn't get a direct answer on it. Could someone confirm it?

 

Thanks

[tomgwyther]

The diaphram is not a smooth muscle, it is skeletal although it is often mistaken for being a smooth muscle.

I found this on chantuer.net, amongst many other similar explanations.

 

"The diaphragm has ONLY skeletal muscle, not smooth muscle - none. It will not contract spontaneously as cardiac muscle. It MUST have an impulse delivered to contract. That impulse can originate in the higher brain centers as when we voluntarily inhale and exhale or in the lower brain as when low oxygen levels or high levels of acid or carbon dioxide are present in the cerebrospinal fluid or blood. "

[historian3x]

Thank you

[cbrons]

Nope, definitely skeletal muscle. Pretty big one too... intimately involved in respiration (inspiration to be exact). Innervated by the phrenic nerve, which arises from spinal nerves C3, C4, and C5 (also innervates the parietal paricardium (covering of the heart) and the pleura on the mediastinal side (side of the pleural cavity of the lungs facing the compartment of the thorax where the heart is situated). Incidentally chronic and severe hiccups can be treated surgically by crushing or sectioning this very same nerve).