Pineal gland
Glandula pinealis
Endocrine & glandsGlandsHead
- What it is
- A tiny pine-cone-shaped gland in the exact midline of the brain, tucked behind the third ventricle above the midbrain. It receives light information from the eyes by a roundabout nerve route via the neck.
- Function
- Secretes melatonin during darkness, setting the body's day–night (circadian) rhythm and, in childhood, restraining puberty.
- Size
- 5–8 mm long, ~5 mm wide, 100–150 mg
- Clinical note
- It calcifies with age ("brain sand"), so it shows up on skull X-rays and CT scans as a midline marker — a shifted pineal was once a classic sign of a mass pushing the brain sideways.