Etymed
diaphragm
Definition
The dome-shaped musculotendinous partition that separates the thoracic cavity from the abdominal cavity and serves as the primary muscle of respiration. Although classified functionally as a respiratory muscle, it is structurally a skeletal (striated) muscle, innervated by the phrenic nerve (C3-C5).
Clinical context
Phrenic nerve injury (C3-C5) paralyzes a hemidiaphragm, which appears abnormally elevated on chest X-ray. Because the diaphragm shares C3-C5 innervation, subdiaphragmatic irritation (blood, abscess, gas) refers pain to the ipsilateral shoulder.
Mnemonic
DIA = 'divide across' - the diaphragm is the muscular wall that divides the chest from the belly.