Sweat glands are responsible for secreting sweat to regulate body temperature.
Tips
usage
泌 is almost always bound rather than standalone. The most common combinations are 分泌 (to secrete) and 内分泌 (endocrine). A separate reading bì appears only in the place name 泌阳 (a county in Henan).
Left three-drops water radical, side form of 水, puts 泌 in the liquid family with 河 (river), 流 (flow), 滴 (drop). The original sense was water trickling through a narrow opening, later borrowed by medicine for 'to secrete'.
Right 必 supplies the sound, bì drifting to mì through regular labial alternation. Same phonetic family: 秘 (secret), 密 (dense), 蜜 (honey). It contributes no transparent meaning here.
