This slide shows a thin section of loose connective tissue (sometimes called areolar tissue). This type of tissue is used extensively throughout the body for fastening down the skin, membranes, blood vessels and nerves as well as binding muscles and other tissues together. It often fills in the spaces between epithelial, muscle and nervous tissue, forming what is known as the stroma of an organ, while the term parenchyma refers to the functional components of an organ. The tissue consists of an extensive network of fibers secreted by cells called fibroblasts. The most numerous of these fibers are the thicker, lightly staining (pink) collagen fibers (1). Thinner, dark-staining elastic fibers (2) composed of the protein elastin can also be seen in the section. s is a slide of a thin section taken from the mammalian kidney showing the many tubular ducts that make up much of this organ. The walls of these ducts (pointed to by the red arrows) are comprised of simple cuboidal epithelial cells, which are usually six-sided in shape but may appear square from a side view.  Note also the thin wall of simple cuboidal epithelium (pointed to by the blue arrow) that forms the top edge of this section.