RESIDENT CELLS OF THE CONNECTIVE TISSUE
MAST CELL
The mast cells are large, round or oval-shaped and often found close to blood vessels.
They participate in inflammatory and allergic reactions by secreting several molecules, such as histamine and heparin, that are accumulated in cytoplasmic vacuoles also called granules.
Their nucleus is usually centrally positioned and many granules can be seen in the cytoplasm.
The granules are usually not well stained by hematoxylin and eosin and for this reason the mast cells are not easily recognized in sections stained with these stains. On the other hand, they stain very well with metachromatic dyes, such as toluidine blue and also by stains for elastic tissue, such as Weigert’s stain.
Metachromatic dyes are so called because they stain cellular structures in a color slightly different from their original color. Mast cell granules, for example, stain purple instead of blue by toluidine blue.
The image is of a whole-mount preparation of a small piece of a mesentery that was stained to demonstrate elastic fibers. The mast cell nucleus is not stained, but its cytoplasm is filled with granules.
The thin fibrils are elastic fibers of the extracellular matrix.
They participate in inflammatory and allergic reactions by secreting several molecules, such as histamine and heparin, that are accumulated in cytoplasmic vacuoles also called granules.
Their nucleus is usually centrally positioned and many granules can be seen in the cytoplasm.
The granules are usually not well stained by hematoxylin and eosin and for this reason the mast cells are not easily recognized in sections stained with these stains. On the other hand, they stain very well with metachromatic dyes, such as toluidine blue and also by stains for elastic tissue, such as Weigert’s stain.
Metachromatic dyes are so called because they stain cellular structures in a color slightly different from their original color. Mast cell granules, for example, stain purple instead of blue by toluidine blue.
The image is of a whole-mount preparation of a small piece of a mesentery that was stained to demonstrate elastic fibers. The mast cell nucleus is not stained, but its cytoplasm is filled with granules.
The thin fibrils are elastic fibers of the extracellular matrix.
Whole mount of mesentery. Staining: Weigert. Large magnification.