Final answer:
Blocking oxytocin receptors inhibits the ejection of milk into the lactiferous sinuses due to the lack of stimulation of myoepithelial cells that are required for the milk ejection ('let-down') reflex.
Step-by-step explanation:
When oxytocin receptors are blocked, the response related to milk ejection from the mammary glands is inhibited. Specifically, oxytocin is a hormone released from the posterior pituitary that stimulates the contraction of myoepithelial cells surrounding the alveoli in the mammary glands. These contractions are crucial for forcing milk from the alveoli into the ducts and eventually into the lactiferous sinuses for the baby to consume. If oxytocin's action is impeded, milk would not be ejected into the lactiferous sinuses, and therefore, the correct answer to the student's question is C) milk will not be ejected into the lactiferous sinuses.
Oxytocin's role is separate from the milk production process, which is primarily controlled by the hormone prolactin. Therefore, if oxytocin receptors are blocked, milk production may still occur but the let-down reflex that allows the milk to be delivered to the suckling infant would be disrupted.