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

Step 1: List the four embryonic contributors to the diaphragm. The diaphragm forms from the septum transversum, the paired pleuroperitoneal membranes, the dorsal mesentery of the oesophagus, and muscle from the cervical myotomes of somites C3 to C5.
Step 2: Match each part. The septum transversum becomes the central tendon. The pleuroperitoneal membranes close the pericardioperitoneal canals and form the dorsolateral part. The dorsal mesentery of the oesophagus forms the crura. The cervical myotomes provide the muscular part along with the phrenic nerve.
Step 3: Check the odd option. The dorsal mesocardium is a fold of mesoderm that suspends the developing heart tube; its breakdown forms the transverse pericardial sinus. It has no role in diaphragm formation.
Step 4: Conclusion. The diaphragm develops from all the listed structures except the dorsal mesocardium.
Hence the correct answer is option B.