This micrograph reveals an extremely cellular loose connective tissue (LCT), also called lamina propria, which is located between the intestinal glands of the colon. The simple columnar mucous secreting epithelial cells seen here represent the glandular tissue. The Mallory stain colors cell nuclei red and collagen blue. Note how the cells are surrounded by a framework of the blue stained collagen fibers. Also shown in this micrograph is a band of smooth muscle, the muscularis mucosa (MM) of the colon and below that, seen in part, is dense irregular connective tissue (DICT) that forms the submucosa of the colon. Typically, the collagen fibers (C) that lie just below the epithelial cells (Ep) at the luminal surface are more concentrated and thus appear prominently in the micrograph.
Loose connective tissue, colon, monkey, threads that form a stroma surrounding the cells. The majority of cells that Mallory, ×700. are present here consists of lymphocytes and plasma cells (P). Other cells that are present within the stromal framework consist of fibroblasts, Shown at higher magnification is the boxed area in the adjasmooth muscle cells, macrophages, and occasional mast cells.
cent figure. The base of the epithelial cells is seen on each side of the micrograph. The collagen fibers (C) appear as thin
KEY CF, collagen fibers DICT, dense irregular connective tissue Ep, epithelial cells GE, glandular epithelium LCT, loose connective tissue MM, muscularis mucosa P, plasma cells
PLATE 5 Dense Regular Connective Tissue, Tendons,and Ligaments 194 Dense regular connective tissue is distinctive in that its fibers are very densely packed and are organized in parallel array into fascicles. The collagen fibrils that make up the fibers are also arranged in an ordered parallel array. Tendons, which attach muscle to bone, and ligaments, which attach bone to bone, are examples of this type of tissue. Ligaments are similar to tendons in most respects, but their fibers and the or-ganization of the fascicles tend to be less ordered. In tendons as well as ligaments, the fascicles are separated from one another by dense irregular connective tissue, the endotendineum, through which travel vessels and nerves. Also, a fascicle may be partially divided by connective tissue septa that extend from the endo-tendineum and contain the smallest vessels and nerves. Some of the fascicles may be grouped into larger functional units by a thicker, sur-rounding connective tissue, the peritendineum. Finally, the fascicles and groups of fascicles are surrounded by dense irregular connective tissue, the epitendineum. The fibroblasts, also called tendinocytes in tendons, are elongated cells that possess exceedingly thin, sheet-like cytoplasmic processes that reside between and embrace adjacent fibers. The margins of the cytoplasmic processes contact those of neighboring tendon cells, thus forming a syncytium-like cytoplasmic network. The most regular dense connective tissue is that of the stroma of the cornea of the eye (see Chapter 24). In this tissue, the collagen fibrils are arranged in parallel in lamellae that are separated by large, flattened fibroblasts. Adjacent lamellae are arranged at approximately right an-gles to one another, thus forming an orthogonal array. The extreme regularity of fibril size and fibril spacing in each lamella, in conjunction with the orthogonal array of the lamellae, is believed to be the basis of corneal transparency.
PLATE 5 • DENSE REGULAR CONNECTIVE TISSUE, TENDONS, AND LIGAMENTS
Dense regular connective tissue, tendon, longitudinal section, human, H&E ×100.