Q.State the role of oxytocin in parturition.
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Let’s begin with something you already know. When a baby is ready to be born, the mother’s body doesn’t just “decide” one day — it follows a precise, hormone-driven sequence. Think of it like a carefully timed relay race: one hormone passes the baton to the next, and each step triggers the next until labour begins.
The everyday intuition
Imagine you are waiting for a train. The station master doesn’t just blow the whistle randomly. First, the train arrives at the platform, then the guard checks the signal, then the whistle blows, and only then does the train move. Parturition — the process of giving birth — works the same way. The baby’s body sends the first signal, the mother’s body receives it, and a chain of hormonal commands follows. No signal, no movement.
What parturition means
Parturition is the medical term for childbirth — the expulsion of the fully developed baby from the mother’s uterus. In NCERT Class 12 Biology (Chapter: Human Reproduction), it is described as the process that begins with the onset of labour and ends with the delivery of the baby and the placenta.
The key point: parturition is not a sudden event. It is the climax of a hormonal cascade that starts weeks earlier.
The hormonal relay: step by step
The entire process is controlled by a feedback loop between the baby’s brain, the mother’s hypothalamus, and her uterus. Here is the sequence as NCERT presents it:
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The baby’s brain starts it. As the foetus grows, its hypothalamus matures and releases corticotropin-releasing hormone (CRH). This hormone travels to the foetal pituitary gland.
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Foetal pituitary secretes ACTH. ACTH (adrenocorticotropic hormone) stimulates the foetal adrenal glands to produce cortisol.
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Cortisol from the foetus acts on the placenta. The placenta, which connects mother and baby, responds by producing oestrogen in increasing amounts. At the same time, progesterone levels fall.
The shift from high progesterone to high oestrogen is the critical switch. Progesterone keeps the uterus relaxed (quiet). Oestrogen makes the uterine muscle sensitive to contraction signals. Without this shift, labour cannot begin.
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Oestrogen stimulates the uterus to produce oxytocin receptors. The mother’s posterior pituitary gland also releases oxytocin — the hormone that causes strong, rhythmic contractions of the uterine muscles.
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Oxytocin creates a positive feedback loop. Each contraction pushes the baby’s head against the cervix. This stretching of the cervix sends nerve signals back to the mother’s brain, which releases more oxytocin. More oxytocin → stronger contractions → more stretching → even more oxytocin. This cycle continues until the baby is delivered.
Why this matters
- It explains why labour cannot be induced artificially without medical intervention — the baby’s own hormones must first signal readiness.
- It also explains why stress or illness in the mother can delay labour: if the foetal cortisol signal is weak, the oestrogen shift may not happen on time.
- In some cases, doctors use synthetic oxytocin (Pitocin) to start or strengthen labour — this mimics the natural hormone.
A quick summary of the key hormones
| Hormone | Source | Role in parturition |
|---|---|---|
| CRH | Foetal hypothalamus | Starts the cascade |
| ACTH | Foetal pituitary | Stimulates foetal adrenal glands |
Oxytocin triggers and intensifies vigorous uterine contractions during childbirth through a positive feedback loop, driving the fetal-ejection reflex and delivery.
From the CBSE/NCERT Human Reproduction chapter, parturition (childbirth) is a neuroendocrine process:
- Signals from the fully developed foetus and the placenta trigger the fetal-ejection reflex.
- This stimulates release of oxytocin from the maternal posterior pituitary.
- Oxytocin acts on the uterine smooth muscle (myometrium), causing strong contractions. …
Showing the 12 most recent of 21 on this concept.
- CBSE 2026Set 57/3/11 markMCQQ.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
›Reveal solutionSolution
The foetal ejection reflex triggers the release of oxytocin from the maternal pituitary gland, which then drives uterine contractions during childbirth.
The foetal ejection reflex is a beautifully coordinated physiological event that marks the final stage of pregnancy. When the baby's head presses against the cervix and vaginal walls, sensory nerve impulses travel from the cervix to the hypothalamus in the mother's brain. This neural signal is the trigger — it tells the posterior pituitary gland to release oxytocin into the mother's bloodstream.
Oxytocin is the key hormone here. It acts directly on the smooth muscles of the uterus, making them contract more strongly. These contractions push the baby further down, which stretches the cervix even more, which in turn signals the release of even more oxytocin. This is a classic positive feedback loop — the more the uterus contracts, the more oxytocin is released, and the stronger the contractions become. The cycle continues until the baby is delivered.
ImportantThe oxytocin that drives this process comes from the mother's posterior pituitary gland, not from the foetus. The foetal pituitary is not involved in this reflex. …
- CBSE 2026Set V11 markQ.The initial few days of milk produced after parturition is ___________.
›Reveal solutionSolution
The first milk secreted after childbirth is colostrum.
The milk produced by the mammary glands during the initial few days after parturition (childbirth) is called colostrum. It is yellowish, and is rich in antibodies (especially IgA) that provide essential passive immuni …
- CBSE 2026Set ANNUAL1 markMCQQ.Which hormone is involved to induce parturition?(a) Prolactin(b) Adrenaline(c) Oxytocin(d) Progesterone
›Reveal solutionSolution
Parturition (delivery) is induced by a neuro-endocrine reflex in which the posterior pituitary hormone oxytocin causes powerful uterine contractions.
At the end of pregnancy, signals from the fully-developed foetus and the placenta induce mild uterine contractions called the 'foetal ejection reflex'. This triggers release of oxytocin from the maternal posterior pituitary, which acts on the uterine (myometrial) muscle causing strong contractions, which in turn stimulate further oxytocin release (a positiv …
- CBSE 2026Set ANNUAL1 markQ.The milk produced during the initial few days of lactation is called ________.
›Reveal solutionSolution
The yellowish fluid secreted by the mammary glands during the first few days of lactation is called colostrum, and it is rich in antibodies (IgA) essential for building the newborn's immunity.
After parturition, the mammary glands of the mother start producing milk (lactation) under the stimulus of the hormone prolactin. The milk produced during the initial few days of lactation is called colostrum. Colostrum contains several antibodies (mainly Immunoglobulin A, IgA) that are absolutely essential for building the immune system (passive im …
- CBSE 2026Set ANNUAL1 markQ.Why is mother's milk considered very essential for the new-born infants?
›Reveal solutionSolution
Mother's milk (colostrum) supplies antibodies (IgA) for passive immunity plus complete nutrition, protecting the newborn.
The milk produced during the initial few days of lactation is called colostrum. It is yellowish and contains several antibodies, chiefly immunoglobulin A (IgA). Since the newborn's own immune system is not yet developed, these maternal antibodies provide passive immunity that protects the infant against infections.
…
- CBSE 2025Set X11 markQ.____________ acts on uterine muscle and cause stronger contractions during parturition.
›Reveal solutionSolution
Oxytocin causes strong uterine contractions during childbirth.
Oxytocin, released from the posterior pituitary, acts on the smooth muscles of the uterus and causes stronger contractions during parturition (childbirth). A vigorous positive feedback loop (foetal ejec …
- CBSE 2025Set A1 markQ.Answer in one word / sentence: What is Colostrum?
›Reveal solutionSolution
Colostrum is the first milk produced after childbirth, rich in maternal antibodies that protect the newborn.
During the initial days of lactation, the mammary glands secrete a special milk called colostrum. It is yellowish and thick, and importantly contains a high concentration of immunoglobulins (mainly IgA) along with other nutrients. These maternal antibodies passed to the infant through colostrum provide passive immunity, helping protect the newborn from infections until its own immune sys …
- CBSE 2025Set ANNUAL1 markQ.Define parturition.
›Reveal solutionSolution
Parturition is the hormonally triggered process of childbirth, marking the end of gestation.
Parturition refers to the process of delivery of the fully developed foetus (and, subsequently, the placenta) from the uterus, marking the end of a full-term pregnancy (about 9 months/40 weeks in humans). It is induced by complex neuroendocrine signals, involving mild uterine contractions (Ferguson's reflex) initiated by signals from the fully developed foetus and the placenta, which stimulate release of the hormone oxytocin from the mother's pituitary; oxytocin acts on the uterine mu …
- CBSE 2024Set A11 markQ.The hormone which helps in Parturition is ____________.
›Reveal solutionSolution
Oxytocin triggers the vigorous uterine contractions that cause parturition (childbirth).
Parturition is the process of delivery of the foetus. It is induced by a complex neuroendocrine mechanism: signals from the fully developed foetus and placenta trigger the release of oxytocin from the mat …
- CBSE 2024Set ANNUAL1 markQ.Why is colostrum very much essential for new born infants?
›Reveal solutionSolution
Colostrum provides the newborn with maternal antibodies and nutrients critical for building the infant's early immune defence.
Colostrum is the thick, yellowish milk secreted by the mammary glands during the first few days after parturition, before regular/mature milk production begins. It is especially rich in immunoglobulins, particularly IgA (secretory antibodies), which the infant's own immune system cannot yet produce in adequate amounts. These maternal antibodies pass into the infant's gut and confer passive immunity, protecting the newborn against various infections during the vulnerabl …
- CBSE 2024Set ANNUAL1 markMCQQ.The yellowish fluid colostrum secreted by mother during the initial days of lactation has antibodies(a) Ig E(b) Ig A(c) Ig M(d) Ig G
›Reveal solutionSolution
Colostrum's protective antibodies are predominantly IgA, giving the newborn passive mucosal immunity.
Colostrum, the thick yellowish fluid secreted by the mammary glands during the first few days after childbirth (before regular breast milk is produced), is especially rich in Immunoglobulin A (IgA) antibodies. IgA is well suited to protect mucosal surfaces (like the infant's gut lining), providing the newborn with essential passive immunity against various infections dur …
- CBSE 2023Set ANNUAL1 markQ.What is foetal ejection reflex?
›Reveal solutionSolution
A positive-feedback hormonal reflex, triggered near full term, that initiates labour and childbirth.
Towards the end of pregnancy (around nine months), signals originating from the fully developed foetus and the placenta bring about mild contractions of the uterus, referred to as the foetal ejection reflex. This reflex induces the release of the hormone oxytocin from the maternal pituitary gland. Oxytocin acts on the uterine (myometrial) smooth muscle, causing strong contractions of the uterus, which in turn stimulates still more oxytocin release — a self-reinforcing positive-feedback loop. This progressively intensifying cycle of contractions ultimately leads to expulsion of the f …
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