The pineal gland (also called the pineal body, epiphysis cerebri, epiphysis, conarium or the 'third eye') is a small endocrine gland in the vertebrate brain. It produces the serotonin derivative melatonin, a hormone that affects the modulation of wake/sleep patterns and seasonal functions. Its shape resembles a tiny pine cone (hence its name), and it is located near the centre of the brain, between the two hemispheres, tucked in a groove where the two rounded thalamic bodies join. The pineal gland is reddish-gray and about the size of a grain of rice (58 mm) in humans, located just rostro-dorsal to the superior colliculus and behind and beneath the stria medullaris, between the laterally positioned thalamic bodies. It is part of the epithalamus. The pineal gland is a midline structure shaped like a pine cone, and is often seen in plain skull X-rays, as it is often calcified; calcification has been shown in one small study to correlate with the accumulation of fluoride.
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