Structure and function of the thyroid gland
Thyroidusually it consists of two parts, connected by an isthmus. Thick fibroznaya capsule, covering the thyroid gland, introduced into it, forming connective septum (stroma glands), which are blood and lymph vessels and nerves. These partitions divide the thyroid lobes and segments on different sizes. The connective tissue septa is a small amount lymphoid cells.
The parenchyma of the thyroid glandIt consists of follicles, are closed bubbles, filled with colloid. The walls are lined with a single layer of follicle epithelium, which in some places is becoming multilane. The shape of epithelial cells, their volume and height depends on the functional activity of the thyroid gland. During normal operations gland epithelial cells of small size, cubical. At a high functional activity of thyroid follicle cell walls as releasing hormone assume a cylindrical shape. The weakening of activity of the gland is accompanied by accumulation of hormones in the cytoplasm of cells, in connection with which they are flattened.
Cages, lining the cavity of the follicle, referred to A cells (follicular cells, tirocitami). They make up the bulk of the cells of the thyroid gland and are involved in the synthesis of iodinated thyroid hormones - thyroxine and triiodothyronine.
Apart from these cells in the follicles secrete two kinds of cells - B-cell (cells Askanaz, cellGertle, onkotsity)and C-cell (okolofollikulyarnye). B-cells are located in the center of follicles, A-cells among or between follicles. They take part in the accumulation of biogenic monoamines (Serotonin). Parafollicular C-cells are located, synthesize the hormone calcitonin.
Hormones, produced in the thyroid gland, stimulate metabolism, It affects the nervous system, skeletal growth, in particular enchondral ossification, and, as antagonists parathyrin, reduces blood levels of calcium.
