An expectant mother tells the nurse that she is concerned about breastfeeding and asks the nurse how her body knows that it is time to produce milk. The nurse's best response regarding stimulus for milk production is that delivery of the fetus:

Correct Answer: A

Rationale: Delivery of the fetus triggers events increasing prolactin levels placental expulsion drops progesterone/estrogen, relieving anterior pituitary inhibition, boosting prolactin for milk synthesis. Oxytocin, also rising, aids ejection, not production. Estrogen drops post-delivery, not rapidly increasing high levels suppress lactation. Prolactin's surge, driven by hormonal shifts and suckling, distinguishes it, key to lactogenesis, unlike ejection or estrogen dynamics.

Correct Answer: C

Rationale: Iodide enters thyroid follicle cells via active transport, using the sodium-iodide symporter (NIS), against its gradient, powered by sodium's electrochemical gradient. Simple diffusion lacks a carrier, facilitated diffusion doesn't use energy, and osmosis moves water. Active transport's energy dependence distinguishes it, essential for thyroid hormone synthesis, concentrating iodide for T3/T4 production.

Correct Answer: C

Rationale: Gonads (ovaries, testes) produce steroid hormones estrogens, progesterone, testosterone from cholesterol, acting intracellularly to regulate reproduction. Amine hormones (e.g., thyroid) derive from tyrosine, peptides (e.g., insulin) from amino acids, and catecholamines (e.g., epinephrine) from adrenal medulla. Steroid's lipid-based nature distinguishes gonadal output, critical for sexual development, contrasting with other chemical classes.

Correct Answer: A

Rationale: The anterior pituitary arises from oral ectoderm, specifically Rathke's pouch, during embryogenesis, forming hormone-secreting cells. Neural ectoderm forms the nervous system (including posterior pituitary), mesoderm muscles/bones, and endoderm digestive organs. Oral ectoderm origin distinguishes anterior pituitary development, key to its endocrine role, contrasting with neural or internal layer derivatives.

Correct Answer: D

Rationale: Directing blood flow is a circulatory system function, adjusting tissue perfusion via vessels to maintain homeostasis, not an endocrine role. The endocrine system regulates immunity (e.g., cortisol affects immune cells), reproduction (e.g., FSH, LH drive gonadal function), and heart rate/blood pressure (e.g., epinephrine increases both), using hormones like adrenaline or aldosterone. Water balance, another endocrine task (e.g., ADH), was replaced here to fit four options, but blood flow direction relies on vascular dynamics, not glandular secretion. This distinction highlights endocrine's chemical signaling versus circulatory mechanics, key to system roles.