Having no ducts or passages, especially used to describe glands that release hormones directly into the bloodstream instead of through tubes.
From 'duct' (from Latin ductus, meaning 'led' or 'conducted') plus the suffix '-less' meaning 'without.' The term emerged in medical terminology in the 19th century to distinguish endocrine glands from exocrine glands.
Your thyroid and pituitary glands are ductless—they're sneaky because they dump hormones directly into your blood rather than using tubes like salivary glands do. It's like the difference between a water pipe and a sprinkler system!
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