The posterior pituitary (or neurohypophysis) is the posterior lobe of the pituitary gland, which is part of the endocrine system releases vasopressin and oxytocin. These products are stored in vesicles at the end of neurosecretory axons in the neurohypophysis and secreted by a calcium-dependent process of exocytosis. Oxytocin mediates contraction of the smooth muscle of the uterus and mammary gland.
Thus, the correct answer is option B.