Connective tissues of the body are defined as the materials which connect other tissue types together. This can be as simple as the basement membrane associated with epithelial types, or as complex as the long bones of the body. Generally, the types of connective tissues are divided into six main groups:
In each case, one should study both the cell types present and the characteristics of the extra-cellular matrix materials. Generally, it is the composition of the extra-cellular matrix which determines the classification of the connective tissue type.
Loose connective tissue (LCT) is literally found everywhere in the body, as filling between apposed body parts. It is also called areolar tissue. It consists of both fibrous extracellular molecules and a number of different cell types. In whole mount spreads of areolar tissue the extracellular fibers are very evident. Collagen, a tough, supporting fiber, appears as wide pink stained bundles, where as elastin fibers appear as thin black line (Areolar Tissue). Within these spreads the predominant cell type, the fibroblast, is also observed. In sections, LCT contains obvious collagen bundles, fibroblasts, and capillaries with their associated pericytes (Loose Connective Tissue). The "open"areas in this micrograph are filled with the amorphous matrix molecules, glycosaminoglycans and proteoglycans. LCT matrix molecules also exist within organs providing support for the resident cells. These fibers, reticular fibers, are arranged in a mesh-like arrangement through organs (Reticular Fibers). Elastin fibers are also found in many organs, and with special stains are visible in a "ribbon candy" morphology (Elastin Fibers).
Adipose or fat tissue is the padding of the body. It is organized into groups of cells called lobules which are separated by collagenous and reticular connective tissue septa (Adipose Tissue). In the formation of a fat cell the cell produces numerous lipid containing vesicles which fuse into one large intracellular lipid droplet. The cell (Adipocyte) becomes so full of lipid that the nucleus and other cellular organelles become compressed into a small crescent of cytoplasm . Unless fixed by a special fixative (osmium tetroxide), lipids are lost from the tissue during dehydration. Therefore, in a routine preparation, the cells appear empty, giving them a ringlike appearance (Adipocyte). Fixation with osmium tetroxide preserves the lipids and strains them black (Adipose Tissue w/ Osmium).
See if you can identify the following tissues, cells, and/or matrix materials:
Scope 1 Scope 2 Scope 3 Answers
