Question

Oxytocin and Vasopressin are secreted by:

• A. Anterior pituitary
• B. Posterior pituitary
• C. Hypothalamus
• D. Adrenal gland

Hint:

Remember that the posterior pituitary (neurohypophysis) does not synthesize any hormones of its own.
It only stores and secretes hormones that are synthesized by the hypothalamus.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question is based on the human endocrine system, specifically the site of secretion of neurohypophyseal hormones.
It requires identifying which gland is responsible for releasing oxytocin and vasopressin into the systemic circulation.

Step 2: Key Formula or Approach:
This is a concept-based biology question.
The approach involves distinguishing between the site of hormone synthesis and the site of hormone secretion.

Step 3: Detailed Explanation:

• Oxytocin and vasopressin (or antidiuretic hormone, ADH) are nonapeptides synthesized in the hypothalamus.

• Specifically, oxytocin is synthesized in the neurons of the paraventricular nucleus, while vasopressin is synthesized in the supraoptic nucleus.

• Following synthesis, these hormones are packaged into secretory granules and transported axonally down the hypothalamo-hypophyseal tract.

• They terminate and are stored in the posterior pituitary gland (neurohypophysis) in specialized axon terminals called Herring bodies.

• Upon stimulation by appropriate electrical signals, these hormones are released via exocytosis into the capillary plexus of the posterior pituitary.

• Thus, while the hypothalamus is the site of synthesis, the posterior pituitary is the anatomical site of storage and secretion into the bloodstream.


Step 4: Final Answer:
Since the question asks which organ secretes these hormones, the correct option is the posterior pituitary.