Q.37 Hormones are released in
Hormones are released directly into the blood by endocrine glands, making option (2) correct.
Question Breakdown
Endocrine glands (ductless) secrete hormones as chemical messengers that travel via bloodstream to target organs, unlike exocrine glands (with ducts). This defines endocrine function across systems like pituitary, thyroid, adrenals.
Option Analysis
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(1) Lumen of endocrine gland: Incorrect; lumen refers to duct-containing exocrine glands (e.g., salivary)—endocrine glands lack ducts.
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(2) Blood: Correct; hormones enter capillaries surrounding endocrine cells, achieving systemic distribution for regulation.
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(3) Outside the endocrine gland: Incorrect; too vague—exocrine secretions go outside via ducts, but hormones diffuse internally to blood.
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(4) Blood cells: Incorrect; hormones aren’t stored/released from blood cells (e.g., RBCs)—they circulate dissolved or bound to carriers.
Hormones released in endocrine gland bloodstream defines endocrine system function, crucial for GATE Life Sciences physiology MCQs. Ductless glands like thyroid (thyroxine) and pancreas (insulin) secrete directly into capillaries for distant target action.
Endocrine Secretion Mechanism
Hormones synthesized in endocrine cells diffuse across basement membrane into fenestrated capillaries, binding plasma proteins for transport. Negative feedback regulates release.
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Stimuli: Hormonal (e.g., TRH → TSH), neural, humoral.
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Circulation: Half-lives vary (minutes for ACTH, days for thyroid).
Comparison Table
| Gland Type | Secretion Site | Examples | Ducts? |
|---|---|---|---|
| Endocrine | Blood | Pituitary, adrenals | No |
| Exocrine | External lumen/ducts | Salivary, sweat | Yes |
Exam Strategy
GATE distinguishes endocrine (blood) vs. exocrine (lumen). Trap: “Outside gland” confuses with exocrine. Key: “Hormones = blood-borne messengers.” Master for hormone pathways questions.
