Final answer:
The two hormones released by the posterior pituitary are oxytocin and vasopressin (antidiuretic hormone, ADH). They are produced in the hypothalamus and their release is regulated by it through blood osmolarity and bodily triggers like childbirth or suckling.
Step-by-step explanation:
The posterior pituitary gland releases two critical hormones: oxytocin and vasopressin (also known as antidiuretic hormone, or ADH). The hypothalamus controls the release of these hormones, which are produced by hypothalamic neurons. These hormones are then transported down the nerve cell axons to the posterior pituitary.
The hypothalamus contains osmoreceptors that detect changes in blood osmolarity (concentration of solutes). When osmolarity is high (suggesting dehydration), the hypothalamus signals the posterior pituitary to release vasopressin. This hormone helps to conserve water by reducing urine output and directing the kidneys to reabsorb more water. Conversely, when the hypothalamus detects a low blood osmolarity or blood pressure, it may inhibit the release of vasopressin.
Oxytocin is primarily involved in childbirth and lactation. Its release is triggered by nerve impulses associated with childbirth and by the suckling of an infant at the breast, which sends a signal back to the hypothalamus. The hypothalamus, in turn, triggers the posterior pituitary to release oxytocin, which facilitates labor and milk ejection.