Expected headings
"Embryology"
"Physiology"
"The pineal gland produces melatonin (N-acetyl-5-methoxytryptamine), a derivative of serotonin (O-methylated and N-acetylated) 13, which affects the modulation of wake/sleep patterns and photoperiodic (seasonal) functions. It is also thought to have a reproductive function and has been associated with the onset of puberty 7. In truth, there are several "organs" responsible for the synthesis of melatonin; among these we recall: the retina, the Harder glands and the mucosa of the gastrointestinal tract. Megakaryocytes and platelets also contribute to its synthesis 14,15. Unlike much of the rest of the brain, the pineal gland is not isolated from the body by the blood-brain barrier."