Structure and Composition
The pineal body consists in humans of a lobular parenchyma of pinealocytes surrounded by connective tissue spaces. The gland's surface is covered by a pial capsule.
The pineal gland consists mainly of pinealocytes, but four other cell types have been identified. As it is quite cellular (in relation to the cortex and white matter) it may be mistaken for a neoplasm.
| Cell type | Description |
|---|---|
| Pinealocytes | The pinealocytes consist of a cell body with 4–6 processes emerging. They produce and secrete melatonin. The pinealocytes can be stained by special silver impregnation methods. Their cytoplasm is lightly basophilic. With special stains, pinealocytes exhibit lengthy, branched cytoplasmic processes which extend to the connective septa and its blood vessels. |
| Interstitial cells | Interstitial cells are located between the pinealocytes. They have elongated nuclei and a cytoplasm which is stained darker than that of the pinealocytes. |
| Perivascular phagocyte | Many capillaries are present in the gland, and perivascular phagocytes are located close to these blood vessels. The perivascular phagocytes are antigen presenting cells. |
| pineal neurons | In higher vertebrates neurons are located in the pineal gland. However, these are not present in rodents. |
| peptidergic neuron-like cells | In some species, neuronal-like peptidergic cells are present. These cells might have a paracrine regulatory function. |
The pineal gland receives a sympathetic innervation from the superior cervical ganglion. However, a parasympathetic innervation from the sphenopalatine and otic ganglia is also present. Further, some nerve fibers penetrate into the pineal gland via the pineal stalk (central innervation). Finally, neurons in the trigeminal ganglion innervate the gland with nerve fibers containing the neuropeptide, PACAP. Human follicles contain a variable quantity of gritty material, called corpora arenacea (or "acervuli," or "brain sand"). Chemical analysis shows that they are composed of calcium phosphate, calcium carbonate, magnesium phosphate, and ammonium phosphate. In 2002, deposits of the calcite form of calcium carbonate were described. Calcium, phosphorus deposits in the pineal gland have been linked with aging.
Read more about this topic: Pineal Gland
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