Development and Congenital Anomalies of the Respiratory Diaphragm

🔹 Gross Anatomy
- Primary muscle of respiration, separating thoracic & abdominal cavities.
- Parts: Central tendon (fibrous), muscular portions (sternal, costal, lumbar).
- Openings:
- T8 – Caval (IVC, right phrenic nerve).
- T10– Esophageal (esophagus, vagus nerves).
- T12 – Aortic (aorta, thoracic duct, azygos vein).
- Nerve Supply: Phrenic nerve (C3, C4, C5).
- Blood Supply: Pericardiacophrenic, musculophrenic, and inferior phrenic arteries.

🔹 Embryology
- Derived from 4 structures
1. Septum transversum → Central tendon.
2. Pleuroperitoneal membranes → Closes pericardioperitoneal canals.
3. Dorsal mesentery of esophagus → Forms crura.
4. Body wall mesoderm → Peripheral muscle.
- Development:
- Week 4– Septum transversum forms.
- Weeks 6–7 – Pleuroperitoneal folds fuse.
- Week 8 – Diaphragm descends to final position.

🔹 Clinical Correlations
- Congenital Diaphragmatic Hernia (CDH) (Bochdalek, Morgagni).
- Eventration of the Diaphragm (weak musculature, paradoxical movement).
- Phrenic Nerve Injury (Paralysis, paradoxical movement).
- Referred Pain (shoulder pain via C3–C5).

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