The pineal body: cones, clocks and sand
What is it? A small gland that sits near the centre of our brain, in a groove between each hemisphere (side). In children it’s only about 8mm long and maybe 9mm wide, and it gets even smaller as we get older. It’s part of the body’s endocrine system, which means it produces hormones that travel to other, target, organs and thus regulate body processes. Where does the name come from? Pineal is from Latin word pinea , which means pine cone— it’s said to be shaped like one. What’s it got to do with sleep? It makes the hormone melatonin, but relatively little is understood about the effect that either this tiny gland, or melatonin, has on the body. Melatonin is secreted particularly during the night rather than the day. In some animals the pineal gland is directly sensitive to light, but in humans, cells in our eye transmit signals to the gland, telling it when it’s light and dark.
This rhythmical cycle of melatonin secretion is believed to regulate the body’s internal clock, telling us when to sleep and when to wake up.
For these reasons some researchers believe taking melatonin can help treat sleep problems such as jet lag and insomnia, especially in the elderly, as we seem to produce less melatonin as we get older. Why might you see your own pineal body? It sometimes has small deposits of calcium in it, and these can show up on skull X-rays. These little gritty particles are called ‘‘ brain sand’’.