A small cone-shaped gland situated below the corpus callosum in the brain, which produces melatonin and is believed to be associated with the circadian rhythm.
A pea-sized mass of tissue attached by a stalk to the posterior wall of the third ventricle of the brain, deep between the cerebral hemispheres at the back of the skull. It may play a part in initiating the development of the gonads but this is uncertain; in other mammals it secretes the hormonelike substance melatonin. The gland becomes calcified as age progresses, providing a useful landmark in X-rays of the skull.