Collagen has an unusual amino acid composition and sequence: Glycine is found at almost every third residue. Collagen contains two uncommon derivative amino acids not directly inserted during translation.
Adult Connective Tissue Connective Tissue Proper The loose or areolar connective tissue is made up of many cell types and intercellular materials matrixwhich also comprise other connective tissues but in varying proportions. It is widely distributed in the body and is found most readily beneath the skin and superficial fascia fatty connective tissueseparating muscles, in all potential spaces, and beneath the epithelial lining in the lamina propria of the digestive system.
This web-like tissue binds cells and organs together but permits these cells and organs to move, as necessary, in relation to each other. Because it is composed of a large amount of amorphous ground substance whose consistency varies from liquid to gelit allows wandering cells to move around freely and other structures, such as blood vessels and nerve, to pass through it.
This connective tissue is important, because of its cellular content, for defense against infection and the repair of damaged tissues.
Important cells found in the loose connective tissue include the following: Fibroblasts, which synthesize collagenous connective tissue fibers that are flexible but of great tensile strength; macrophages or histiocytes and monocytes, which ingest, digest, or "store" microscopic particles such as debris of dead cells; certain microorganisms; and other non-biodegradable matter.
Capable of ameboid movement, these cells wander throughout the connective tissue and congregate in regions requiring their specialized function. Mast cells synthesize and release substances of physiological importance e. Heparin is a powerful anticoagulant of blood, whereas histamine increases the permeability of blood capillaries.
Circulating eosinophils increase in number in parasitic infections and in hypersensitivity reactions, such as in hay fever and asthma. Factors within the specific granules of eosinophils are thought to function as anti-larval agents in helminthic infections; additional factors can be directed against histamine and other inflammatory agents.
Lymphocytes and plasma cells also populate loose connective tissue and play a vital role in the defense mechanism by producing antibodies, the immunoglobulins of the blood.
Eosinophils, lymphocytes, and plasma cells are particularly abundant in the lamina propria of the digestive system Plates 29 and and other potentially vulnerable areas of the body.
In the digestive system and elsewhere, the individual is separated from pathogenic organisms of the external environment by only a delicate single cell layer.
This cell layer is essential for absorption, excretion, and gaseous exchange; it is therefore vital to maintain defensive cells just below the vulnerable surface. Fat cells may occur singly or in small or large numbers. When fat cells predominate, the tissue is called adipose tissue.
One of the special connective tissues, adipose tissue, serves as a reservoir of energy and as a soft packing in potential spaces e.
It also envelopes glands that undergo cyclic or functional variation in size and activity e. The more important intercellular components of the loose connective tissue include three kinds of fibers collagenous, previously mentioned, and elastic and reticular and amorphous ground substance.
Collagenous and reticular fibers belong to the same class of protein, collagen, whereas elastic fibers are formed of elastin. There are many kinds of collagen, and it is the most abundant protein of the human body about 30 percent of the dry weight.
Ground substance is composed primarily of two classes of compounds: The term glycosaminoglycan is replacing the older, but widely used, term mucopolysaccharide to denote a linear polysaccharide with characteristic repeating disaccharide units.
The repeating units are usually a uronic acid and a hexosamine. The uronic acid may be glucuronic or iduronic acid, and the hexosamine may be glucosamine or galactosamine.
The structural glycoproteins play an important role in cell interaction and in migration and adhesion of cells. Fibronectin, laminin, and chondronectin are three structural glycoproteins; these cannot, however, be distinguished by routine histological techniques.
It might be useful to remember, as you review your microscope slides and the photomicrographs in this book, that collagenous fibers are acidophilic and therefore stain red with eosin, stain blue with Mallory's trichrome, and stain green with Masson's trichrome.
Elastic fibers may or may not stain well with eosin Plate 34 or Masson's stain, and they may or may not stain red or yellow with Mallory's stain; however, old elastic fibers will stain better than younger elastic fibers.
Reticular fibers are argyrophilic and therefore stain with silver stains such as Wilder's method Plate Ground substance or basement membrane is stained by aldehyde fuchsin Plate 20periodic acid-Schiff stain Plateand toluidine blue Plate Dense connective tissue contains fewer cells, but, when they are present, they are similar in type to those found in loose connective tissue.
Collagenous Type 1 fibers predominate in this type of connective tissue. Dense connective tissue appears in two forms: The irregular type is found in the dermis of the skin, deep fascia surrounding and defining muscles, capsules of organs, and nerve sheaths.
Dense regular connective tissue is found mainly in ligaments and tendons Plates 31 and 32which provide flexible but inelastic unions between bones and between bones and skeletal muscle. At low magnification, a tendon may be confused with striated muscle, because the fibers are axially arranged and the alignment of fibroblast nuclei resembles that found in striated muscle.
At higher magnifications, however, the structural differences are easily recognized and a proper identification is readily accomplished.
Other examples of dense regular connective tissue include most ligaments Plate 33aponeuroses, and the cornea of the eye Plate Connective tissues with special characteristics of structure and function include elastic, reticular, and pigmented types.Collagen / ˈ k ɒ l ə dʒ ɪ n / is the main structural protein in the extracellular space in the various connective tissues in animal bodies.
As the main component of connective tissue, it is the most abundant protein in mammals, making 25% to 35% of the whole-body protein content.
Collagen consists of amino acids wound together to form triple-helices to form of elongated fibrils. Standard Process - Manganese B12 - Supports Normal Tissue Repair Process and Connective Tissue, Provides Antioxidant Vitamin C, Vitamin B12, Iron, Zinc, Copper, Manganese, Gluten Free - 90 Tablets.
Dense irregular connective tissue provides strength in multiple directions by its dense bundles of fibers arranged in all directions. Special connective tissue consists of reticular connective tissue, adipose tissue, cartilage, and makes up about 25% of the total protein content of the mammalian body.
Types. Connective tissue can be broadly subdivided into connective tissue proper, and special connective tissue.
Connective tissue proper consists of loose connective tissue and dense connective tissue (which is further subdivided into dense regular and dense irregular connective tissues.) Loose and dense connective tissue are distinguished by the ratio of ground substance to fibrous tissue.
extracellular matrix, which surrounds connective tissue cells, consists of a variety of different protein fibers and a ground substance. The type of fibers and components of the ground substance varies depending on the tissue type.
Dense connective tissue can be categorized into dense regular, dense irregular, and elastic connective tissues. Dense regular: Tendons and ligaments are examples of dense regular connective tissue. Dense irregular: Much of the dermis layer of the skin is composed of dense irregular connective tissue.