| Definition: |
This cell type produces and secretes melatonin and forms the pineal parenchyma. Extending from each cell body, which has a spherical, oval or lobulated mucleus, are one or more tortuous basophilic processes, containing parallel microtubules known as synaptic ribbons. These processes end in expanded terminal buds near capillaries or less, frequently, ependymal cells of the pineal recess. The terminal buds contain granular endoplasmic reticulum, mitochondria and electron-dense cored vesicles, which store monoamines and polypeptide hormones, release of which appears to require sympathetic innervation. |