Or pineal gland a cone-shaped outgrowth of the vertebrate brain. In some lower vertebrates, it develops a rudimentary lens and retina, which show it to be derived from an eye, or pair of eyes, situated on the top of the head in ancestral vertebrates. In fishes that can change color to match their background, the pineal perceives the light level and controls the color change. In birds, the pineal detects changes in daylight and stimulates breeding behavior as spring approaches. Mammals also have a pineal gland, but it is located deeper within the brain. It secretes a hormone, melatonin, thought to influence rhythms of activity. In humans, it is a small piece of tissue attached by a stalk to the rear wall of the third ventricle of the brain.
Koštana jabučica, okrajci dugih kostiju; mala endokrina žlezda koja se nalazi u zadnjem delu srednje komore mozga, važna za razvitak telesnih i spolnih osobina čoveka, naročito po tome što reguliše i koči prerano razvijanje spolnih obeležja. (grč.)