Anatomy of the diaphragm; Briefly describe the anatomy of the diaphragm

INTRODUCTION: the diaphragm is a dome shaped musculotendinous  partition between the thoracic and abdominal cavities. It forms the floor of the thoracic cavity and the roof of the abdominal cavity. The diaphragm is the principal muscle of respiration.
STRUCTURE: the diaphragm is composed of two portions; a peripheral muscular part and a central aponeurotic part (central tendon)
muscular part: the fibres forming this part converge radially to the central tendon. It is divided into 3 parts: the sternal part, the costal part and the lumbar part.
the central portion: this portion fuses with the inferior surface of the fibrous pericardium. It has no bony attachment.
ARTERIAL SUPPLY.
1. Superior surface:
superior phrenic arteries: from the thoracic aorta
musculophrenic artery: from the internal thoracic artery
pericadiophenic artery: from the internal thoracic artery.
2. Inferior surface:
– inferior phrenic arteries: from the abdominal aorta
– lower 5 intercostal, and subcostal arteries supply the margin
VENOUS DRAINAGE:
1. Superior surface.
pericardiophrenic vein: drains into the internal thoracic vein
musculophrenic vein: drains into the internal thoracic vein
2. inferior surface:
This is drained by the inferior phrenic vein. The right inferior phrenic vein drains into the inferior vena cava while the left drains into the left suprarenal vein
LYMPH DRAINAGE:
Superior surface: lymph drains from here into the parasternal and posterior mediastinal lymph nodes
Inferior surface: lymph from here drains into the superior lumbar lymph nodes.
NERVE SUPPLY:
The entire motor supply is from the phrenic nerve (C3 to C5). The phrenic nerve also provide sensory supply (pain and proprioception) to the diaphragm. The peripheral parts receive their sensory supply from the inferior six or seven intercostal and the subcostal nerve.
ACTION: it is the chief muscle of inspiration. It’s also needed in abdominal straining.
DIAPHRAGMATIC OPENING:
1. Aortic opening: (T12) transmit the abdominal aorta, the thoracic duct and the azygos vein
2. Esophageal opening: (T10) transmits the esophagus, branches of the left gastric vein and the two vagi
3. Inferior vena caval  opening: (T8) transmits the inferior vena cava and the right phrenic nerve.
CLINICAL CORRELATES:
1. Diaphragmatic rupture and herniation can result from a sudden increase in either intrathoracic or intrabdominal pressure
2. Section of the phrenic nerve in the neck results in complete paralysis and eventual atrophy of the corresponding half of the diaphragm

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