

緊張して、心臓がどきどきしています。
祖父は心臓の病気で入院しています。
毎日運動すると、心臓は強くなりますか?
"しんぞう(心臓)" is in the lesson "Body" (Level 27), along with 8 other useful words. LinDuo has 180 topic lessons like this one, 2,379 words in total. Every word has an illustration, a transcription and pronunciation in a female and a male voice. Just 10–15 minutes a day is enough to learn them all. Free, and works offline.