Hormones and Endocrine System

Prolactin stimulates the mammary glands to produce milk, whereas oxytocin stimulates the contraction of myoepithelial cells to cause milk ejection. Estrogen helps prepare the breasts for lactation during pregnancy but does not directly stimulate milk production or ejection.

The pituitary gland secretes hormones that regulate growth, homeostasis, and reproduction. It does not directly control or alter the genome of cells, which is the complete set of genetic material.

Follicle-stimulating hormone (FSH) is synthesized and secreted by the gonadotropic cells of the anterior pituitary gland. This distinguishes it from posterior pituitary hormones, which are synthesized in the hypothalamus.

Oxytocin is synthesized by neuronal cell bodies in the hypothalamus and transported down axons to the posterior pituitary gland. It is stored there and subsequently released into the bloodstream.

Mammary glands are exocrine glands because they secrete milk through ducts to the external environment. In contrast, the adrenal, thyroid, and pituitary glands are endocrine glands that secrete hormones directly into the bloodstream.

Endocrine glands are ductless glands that secrete chemical messengers called hormones directly into the bloodstream to act on distant target organs. Exocrine glands, by contrast, secrete substances into ducts or body cavities.