Endocrine system Endocrine system The endocrine system is a chemical messenger system consisting of hormones, the group of glands of an organism that secrete those hormones directly into the circulatory system to regulate the function of distant target organs, and the feedback loops which modulate hormone release so that homeostasis is maintained. In humans, the major endocrine glands are the thyroid gland and the adrenal glands. In vertebrates, the hypothalamus is the neural control center for all endocrine systems. The study of the endocrine system and its disorders is known as endocrinology. Endocrinology is a branch of internal medicine. Special features of
Labial glands Labial glands The labial glands are minor salivary glands situated between the mucous membrane and the orbicularis oris around the orifice of the mouth. They are circular in form, and about the size of small peas; their ducts open by minute orifices upon the mucous membrane. Like the parotid and buccal glands, the labial glands are innervated by parasympathetic fibres that arise in the inferior salivatory nucleus, travel with the glossopharyngeal nerve and lesser petrosal nerve to the otic ganglion, where they synapse and then continue to the labial glands. Sympathetic innervation is mediated by postganglionary fibres which arise in