The pineal gland, (pineal body ; epiphysis) is a small reddish-gray body, about 8 mm. in length which lies in the depression between the superior colliculi. It is attached to the roof of the third ventricle near its junction with the mid-brain. It develops as an outgrowth from the third ventricle of the brain.
It produces melatonin, a serotoninderived hormone, which affects the modulation of sleep patterns in both seasonal and circadian rhythms.