Oxytocin causes all of the following except?

Appeared in: ISRO- 2016

Explanation

Lactogenesis refers to the synthesis and secretion of milk from the breast alveoli, which is the process of milk production.
This process is primarily stimulated by the hormone Prolactin, which is secreted by the anterior pituitary gland.
Oxytocin, secreted from the posterior pituitary, does not initiate milk production; its role is to eject the milk that has already been produced.

Option A: This is a primary function of oxytocin. It stimulates the smooth muscle of the uterus (myometrium) to contract, which is essential for labor and postpartum recovery.
Option B: This is a key function of oxytocin. It triggers the 'let-down' reflex, which moves milk from the alveoli into the ducts so the baby can feed.
Option D: This is the specific cellular mechanism by which oxytocin causes milk ejection. It binds to receptors on myoepithelial cells, causing them to contract.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Hormonal regulation of lactation and uterine function as background academic context rather than a clinical decision trigger.
Synthetic oxytocin (Pitocin) is a commonly used medication in obstetrics to induce or augment labor and to manage postpartum hemorrhage by ensuring strong uterine contractions.
Nurses providing lactation support must understand the difference between lactogenesis (milk production) and milk ejection (let-down). A mother might be producing enough milk (prolactin is working), but if the oxytocin reflex is inhibited by stress, pain, or anxiety, the baby will have difficulty getting the milk.
What if the question asked which hormone is responsible for milk production? The answer would be Prolactin, which is stimulated by suckling and a decrease in postpartum estrogen and progesterone levels.

How to Approach the Question

First, identify the keyword 'except' in the question stem. This signals that you must find the option that is NOT a function of oxytocin.
Systematically evaluate each option against your knowledge of oxytocin's physiological roles.
Recall that oxytocin's two main functions relate to childbirth and breastfeeding: uterine contractions and milk ejection.
Option A, 'Contraction of uterine muscles,' is a known function. Eliminate it.
Option B, 'Milk ejection,' is also a known function (the let-down reflex). Eliminate it.
Option D, 'Myoepithelial cell contraction,' is the direct mechanism for milk ejection. This is also a function of oxytocin. Eliminate it.

Concept Tested & Keywords

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E6 Physiology Ganong 27e Vol 1 Part 2 p. 92-94

E6 Gynecology Williams p. 365-430

E6 Physiology Essentials Sembulingam 10e Part 2 p. 30-32

Practise the full ISRO- 2016

Attempt every question from this paper in a timed mock, then review the full solution for each one.