Question

__________ is secreted from the posterior pituitary gland and is must for the ejection (milk let-down) of milk.

• A. Somatotropin
• B. Parathyroid
• C. Adrenals
• D. Oxytocin

Hint:

Remember the two key hormones in lactation and their glands: {Prolactin} (from the {anterior} pituitary) is for milk {synthesis}, while {Oxytocin} (from the {posterior} pituitary) is for milk {ejection}.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The question asks to identify the hormone responsible for the milk ejection reflex (also known as milk let-down) and its gland of secretion. This is a fundamental concept in lactation physiology.
Step 2: Detailed Explanation:
Let's examine the options:
(A) Somatotropin: Also known as Growth Hormone (GH), it is secreted by the anterior pituitary gland and is primarily involved in growth and metabolism. While it plays a role in maintaining lactation (galactopoiesis), it does not cause milk let-down.
(B) Parathyroid: This refers to the parathyroid hormone (PTH), which is secreted by the parathyroid glands. Its main function is to regulate calcium and phosphate levels in the blood. It is not involved in milk ejection.
(C) Adrenals: The adrenal glands secrete hormones like adrenaline and cortisol. These are stress hormones and can actually inhibit the milk let-down reflex.
(D) Oxytocin: This hormone is produced in the hypothalamus and stored and released from the posterior pituitary gland. Stimuli like suckling or the sight/sound of the calf trigger its release. Oxytocin acts on the myoepithelial cells surrounding the alveoli in the mammary gland, causing them to contract and eject the milk into the ducts. This process is called the milk let-down reflex.
Step 3: Final Answer:
Oxytocin is the hormone secreted from the posterior pituitary gland that is essential for the ejection of milk.