Pinealotsüütide

Pinealotsüütide, also known as pinealocytes, are the primary parenchymal cells of the pineal gland. These cells are neuroendocrine in nature, meaning they receive neural input and respond by secreting hormones. Pinealocytes are responsible for the synthesis and secretion of melatonin, a hormone that plays a crucial role in regulating circadian rhythms, the body's natural sleep-wake cycles.

Morphologically, pinealocytes are roughly spherical or ovoid cells with large nuclei and prominent nucleoli. They possess abundant cytoplasm containing numerous organelles, including endoplasmic reticulum, Golgi apparatus, and mitochondria, indicative of their active secretory function. There are generally two types of pinealocytes identified: "light" cells and "dark" cells, distinguished by their cytoplasmic density and the amount of stored secretory granules. Light cells are considered more active in melatonin synthesis.

The activity of pinealocytes is regulated by light. Darkness stimulates their activity and melatonin production, while light inhibits it. This photoperiodic control is mediated through a complex pathway involving the retina, the suprachiasmatic nucleus of the hypothalamus, and sympathetic innervation to the pineal gland. Melatonin, once released into the bloodstream, influences various physiological processes, including sleep, mood, and immune function. Disruptions in pinealocyte function or melatonin production are implicated in sleep disorders and other health issues.