Topography and Appearance
The pineal body is an unpaired structure anatomically located in the region of the roof of the third ventricle of the brain.
In shape, the gland is triangular-oval. A characteristic structural feature is that the pineal gland is somewhat flattened in the anteroposterior direction. Its pointed end (apex) is directed strictly posteriorly.
Externally, the organ is covered by the pia mater. This anatomical fact has important practical significance: during brain dissection, this membrane is often removed along with the gland itself, requiring special care from the dissector.
Morphometric Parameters
The size of the pineal body in adults is relatively small, but it has clear normal limits.
Main parameters of the adult pineal gland:
- Longitudinal dimension: 1.0 to 1.2 cm.
- Transverse dimension: 5–8 mm.
- Thickness: 4–5 mm.
- Weight: only about 0.25 grams.
Histological Structure and Age-Related Changes
From the perspective of microscopic anatomy, the parenchyma of the pineal body is formed by two main cell types:
- Pinealocytes — the specific secretory cells of the gland.
- Neuroglial cells — perform supportive, structural, and trophic functions.
An interesting feature of the organ is its pronounced age-related changes. As the body ages, calcium salts begin to deposit in the pineal tissue. Over time, these mineral accumulations form the so-called brain sand (acervulus cerebri), which serves as a normal physiological marker of glandular aging.
Endocrine Function of the Pineal Gland
As a fully functional endocrine gland, the pineal body specializes in the production of the hormone melatonin.
The secretion of this substance ensures several critically important tasks in the body:
- Regulation of circadian and seasonal biological rhythms (sleep-wake cycles, adaptation to seasonal changes).
- Inhibition of the endocrine function of the pituitary gland.
- Suppression of gonadal activity, which is an important mechanism in the overall hormonal regulation system of the body.