Department of Anatomy, Faculty of Medicine, University of Jeddah, Jeddah, Saudi Arabia.
Department of Histology and Cytology, Faculty of Veterinary Medicine, Zagazig University, Zagazig, Egypt.
Open Vet J. 2023 Feb;13(2):206-217. doi: 10.5455/OVJ.2023.v13.i2.9. Epub 2023 Feb 16.
The epiphysis cerebri (pineal gland) is a small-sized, photo neuroendocrine organ in the brain of most vertebrates. Their effect is through secretion of melatonin, a serotonin-derived hormone which is stimulated by darkness and inhibited by light and modulates the circadian rhythm; light and dark cycle like a biological clock, sleep patterns (sleep-wake cycle), and sexual development.
This study aimed to identify and differentiate the different cell types filling the pineal gland parenchyma of mature male sheep.
Pineal glands were collected and sliced parasagitally then processed histologically for light and electron microscopic examinations.
Two main cell types; pinealocytes and astrocytes were recognized within the gland parenchyma. Pinealocytes were the chief parenchymatus cells that occupied the largest volume of the gland and were classified according to the nuclear pictures (activity status) into two subtypes; pinealocytes I (pale subtype, active) and II (dark subtype, inactive). Astrocyte neuroglial cells had cytoplasmic processes which form a huge supportive framework between the pinealocytes and clarified two types; type I were elongated cells with elongated snake shaped nucleus and type II were smaller in size, with oval nuclei. Another marginal cell type was identified as a neuron-like cell which appeared larger in size than others and distributed sporadically, has eccentric oval nucleus with prominent nucleoli and single, long cytoplasmic process that branched at its terminal forming T-shaped process looks like pseudo unipolar neuron. Moreover, aggregations of pigment granules were markedly observed in the intercellular spaces and also near the blood capillaries. With transmission electron microscope (TEM) a special characteristic feature of pinealocytes; synaptic ribbons were recognized that appeared as bands of electron-dense material with several synaptic spherules; vesicles adjacent to its surface helping in the multivesicular release.
The gland parenchyma revealed two main cell types; pinealocytes and astrocytes. Each one was subdivided into two subtypes; I and II. The first one was classified according to their nuclear pictures (activity status) and the second one was according to their shape, size, and cytoplasmic processes. Other cell types were also identified as neuronal and pigmented-like cells in the pineal matrix.
脑垂体（松果体）是大多数脊椎动物大脑中的一个小型光神经内分泌器官。其作用是通过分泌褪黑素来实现，褪黑素是一种由 5-羟色胺衍生而来的激素，受黑暗刺激，受光照抑制，并调节昼夜节律；光暗周期就像生物钟一样，调节睡眠模式（睡眠-觉醒周期）和性发育。
本研究旨在识别和区分成熟雄性绵羊松果体实质中填充的不同细胞类型。
采集松果体并沿矢状位切片，然后进行组织学处理，进行光镜和电镜检查。
在腺实质内识别出两种主要的细胞类型；松果体细胞和星形胶质细胞。松果体细胞是主要的实质细胞，占据腺体的最大体积，并根据核图（活性状态）分为两种亚型；I 型（浅色亚型，活跃）和 II 型（深色亚型，不活跃）。星形胶质细胞神经胶质细胞有细胞质突起，在松果体细胞之间形成巨大的支持框架，并澄清了两种类型；I 型是长形细胞，具有长蛇形核，II 型较小，核呈椭圆形。另一种边缘细胞类型被鉴定为神经元样细胞，其大小大于其他细胞，分布散在，具有偏心的椭圆形核，突出的核仁，单个长的细胞质突起在末端分支形成 T 形突起，看起来像伪单极神经元。此外，在细胞间隙和靠近毛细血管处明显观察到色素颗粒的聚集。用透射电子显微镜（TEM）识别松果体细胞的一个特殊特征；突触带，它表现为电子致密物质带，带有几个突触小球；与表面相邻的小泡，有助于多泡释放。
腺实质显示出两种主要的细胞类型；松果体细胞和星形胶质细胞。每一种都细分为两种亚型；I 和 II。第一种是根据核图（活性状态）分类的，第二种是根据形状、大小和细胞质突起分类的。在松果体基质中还鉴定出其他细胞类型，如神经元样细胞和色素样细胞。
