August 11 by Ray Sahelian, M.
Pre-Lab Reading Introduction Connective tissue is a term used to describe the tissue of mesodermal origin that that forms a matrix beneath the epithelial layer and is a connecting or supporting framework for most of the organs of the body. This lab will focus on the so-called connective tissue proper and cartilage; the next lab will focus on bone.
Overview of Connective Tissue In contrast to epithelia, connective tissue is sparsely populated by cells and contains an extensive extracellular matrix consisting of protein fibers, glycoproteins, and proteoglycans.
The function of this type of tissue is to provide structural and mechanical support for other tissues, and to mediate the exchange of nutrients and waste between the circulation and other tissues.
These tissues have two principal components, an extracellular matrix and a variety of support cells. These two components will be the focus of this lab.
Most frequently, the different types of connective tissues are specified by their content of three distinguishing types of extracellular fibers: Ground Substance The ground substance is an aqueous gel of glycoproteins and proteoglycans that occupies the space between cellular and fibrillar elements of the connective tissue.
It is characterized by a gel-like viscous consistency and is polyanionic. The characteristics of the ground substance determine the permeability of the connective tissue layer to solutes and proteins. Collagenous connective tissue is divided into two types, based upon the ratio of collagen fibers to ground substance: Loose areolar connective tissue is the most abundant form of collagenous connective tissue.
It occurs in small, elongated bundles separated by regions that contain ground substance. Dense connective tissue is enriched in collagen fibers with little ground substance. If the closely packed bundles of fibers are located in one direction, it is called regular; if oriented in multiple directions, it is referred to as irregular.
An example of regular dense connective tissue is that of tendons; an example of irregular dense connective tissue is that of the dermis.
Unlike the thick and coarse collagenous fibers, reticular fibers form a thin reticular network. Such networks are widespread among different tissues and form supporting frameworks in the liver, lymphoid organs, capillary endothelia, and muscle fibers.
Elastic Fibers Elastic fibers contain the protein elastin, which co-polymerizes with the protein fibrillin.
These fibers are often organized into lamellar sheets, as in the walls of arteries. Dense, regular, elastic tissue characterizes ligaments. Elastic fibers are stretchable because they are normally disorganized — stretching these fibers makes them take on an organized structure.
Cells of the Connective Tissue Proper Although the connective tissue has a lower density of cells than the other tissues you will study this year, the cells of these tissues are extremely important.
Fibroblasts are by far the most common native cell type of connective tissue. The fibroblast synthesizes the collagen and ground substance of the extracellular matrix. These cells make a large amount of protein that they secrete to build the connective tissue layer.
Some fibroblasts have a contractile function; these are called myofibroblasts. Chondrocytes and osteocytes form the extracellular matrix of cartilage and bone. More details and chondrocytes can be found later in this laboratory; osteocytes will be covered in the Laboratory on Bone.
The macrophage is the connective tissue representative of the reticuloendothelial, or mononuclear phagocyte, system.Dense connective tissue contains more collagen fibers than does loose connective tissue.
As a consequence, it displays greater resistance to stretching. There are three major categories of dense connective tissue: regular, irregular, and elastic. Connective tissue disease refers to a group of disorders involving the protein-rich tissue that supports organs and other parts of the body.
Examples of . The connective tissues include a variety of cells, non-living cell products, and blood. A classification and a concise discussion of the various connective tissues follows. Connective tissue disease: Connective tissue disease, any of the diseases that affect human connective tissue.
Diseases of the connective tissue can be divided into (1) a group of relatively uncommon genetic disorders that affect the primary structure of connective tissue and (2) a number of acquired maladies in which the. Connective tissue proper includes loose connective tissue and dense connective tissue.
Both tissues have a variety of cell types and protein fibers suspended in a viscous ground substance. Dense connective tissue is reinforced by bundles of fibers that provide tensile strength, elasticity, and protection.
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.