Musculi intercostales interni

Posterior
surface of sternum and costal cartilages, showing Transversus thoracis.
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Schultermuskulatur
von vorne: tiefe Schichten
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A central rib
of the left side. Inferior aspect.
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Internal
oblique muscle, left 
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Diagram of
the course and branches of a typical intercostal nerve.
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Thoracic
portion of the sympathetic trunk.
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Internal
intercostal muscles (shown in red).
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Internal
intercostal muscles (shown in red).
Wikipedia • CC BY-SA 2.1 jp