noun
sinoatrial node
Medical term for the heart's natural pacemaker, located in the right atrium.
洞房結節は心臓の拍動を開始する組織です。
The sinoatrial node is the tissue that initiates the heartbeat.
Compound of 洞房 (dōbō, 'sinus') and 結節 (kessetsu, 'node'). The exact historical derivation is uncertain; the spelling is conventionally associated with the medical meaning.