The pineal gland is an unpaired organ located immediately behind the thalamus. It is part of diencephalon and lies dorsally to it and is attched to it via the habenulae and a short peduncle. It's size varies between species and individuals. It is inervated by the '''postganglionic sympathet
The pineal gland secretes [[Endocrine System - Melatonin - Anatomy & Physiology|melatonin]] in response to day length.
The pineal gland secretes [[Endocrine System - Melatonin - Anatomy & Physiology|melatonin]] in response to day length.