[ ˌɛndəʊ'kα:dɪəm ]
■ noun the thin, smooth membrane which lines the chambers of the heart and forms the surface of the valves.
Origin
C19: mod. L., from endo- + Gk kardia 'heart'.
ENDOCARDIUM
Meaning of ENDOCARDIUM in English
Concise Oxford English vocab. Сжатый оксфордский словарь английского языка. 2004