Question

Foetal ejection reflex in human female triggers the release of which hormone?

• A. Oxytocin from foetal pituitary gland
• B. hCG from placenta
• C. Progesterone from corpus luteum
• D. Oxytocin from maternal pituitary gland

Hint:

Remember that labor and childbirth are controlled by a classic positive-feedback reflex loop. The signal starts from the foetus, but the heavy mechanical force (uterine contractions) is powered by oxytocin released directly from the maternal posterior pituitary gland.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question asks about the specific hormone whose release is triggered by the foetal ejection reflex in a human female, along with the precise anatomical site of its secretion.
The foetal ejection reflex is the neuroendocrine mechanism that initiates parturition (the process of childbirth).

Step 2: Key Formula or Approach:
The process of parturition is governed by a fully coordinated neuroendocrine reflex loop.
The signals for childbirth originate from the fully mature foetus and the placenta, which induce mild uterine contractions. This initial phase is formally defined as the foetal ejection reflex.

Step 3: Detailed Explanation:
When the foetus is completely developed, it, along with the placenta, generates signals that initiate mild, rhythmic contractions of the uterine myometrium.
These mild contractions stimulate the mechanical stretch receptors located in the cervix of the mother.
The activation of these receptors generates nerve impulses that travel via afferent pathways to the maternal hypothalamus.
In response, the maternal hypothalamus signals the posterior pituitary gland (neurohypophysis) to release the hormone oxytocin into the maternal bloodstream.
Oxytocin acts directly on the uterine smooth muscles, causing stronger and more vigorous uterine contractions. These enhanced contractions further stimulate the stretch receptors, leading to an increasing, positive-feedback loop that culminates in the expulsion of the baby.
While the foetal pituitary gland does secrete trace amounts of oxytocin during late pregnancy, it is the maternal pituitary gland that releases the massive surge of oxytocin required to drive the mechanical process of labour.
Therefore, options (A), (B), and (C) are incorrect because hCG maintains the corpus luteum, progesterone maintains pregnancy, and the essential oxytocin surge comes from the mother, not the foetus.

Step 4: Final Answer:
The foetal ejection reflex triggers the release of oxytocin from the maternal pituitary gland, which corresponds perfectly to option (D).