ultimobranchial

The ultimobranchial body is a component of the endocrine system found in many vertebrates, including fish, amphibians, reptiles, and birds. It is derived from the posterior part of the last pharyngeal (gill) pouch. In mammals, the ultimobranchial body is typically incorporated into the thyroid gland during embryonic development and is not considered a distinct organ in adults. The primary function of the ultimobranchial body is the production and secretion of calcitonin, a hormone that plays a crucial role in calcium homeostasis. Calcitonin acts to lower blood calcium levels by inhibiting bone resorption (the breakdown of bone tissue) and reducing calcium reabsorption in the kidneys. This counteracts the effects of parathyroid hormone, which raises blood calcium. The hormone's importance is particularly evident in species with high calcium demands, such as egg-laying females. Research into the ultimobranchial body continues to elucidate its precise roles and mechanisms in different vertebrate groups, contributing to our understanding of endocrine regulation and mineral metabolism.