Question

Diaphragm develops from all except:

• A. Septum transversum
• B. Dorsal mesocardium
• C. Pleuroperitoneal membrane
• D. Cervical myotomes

Hint:

Dorsal mesocardium forms the transverse pericardial sinus, not the diaphragm.

Answer 1

The Correct Option is B

Build the diaphragm piece by piece from its known sources and then spot the impostor in the list. The classic four components are the septum transversum, the two pleuroperitoneal membranes, the dorsal mesentery of the oesophagus, and migrating muscle from the cervical myotomes that drags the phrenic nerve down with it.

The septum transversum hardens into the central tendon, the pleuroperitoneal membranes seal off the dorsolateral gaps, and the cervical myotomes deliver the contractile muscle. The dorsal mesocardium, however, belongs to the story of the heart: it is the mesodermal sling that holds the heart tube and later perforates to create the transverse pericardial sinus. It contributes nothing to the diaphragm. So among the choices the dorsal mesocardium is the one that does not take part.
\[\boxed{\text{Dorsal mesocardium}}\]