Page 166 - Atlas of Histology with Functional Correlations

CHAPTER 5 Connective Tissue

Connective tissue originates from embryonic mesenchyme cells that
differentiate during development into cell types that include cartilage, bone, and
blood. Because mesenchyme cells can differentiate into different cells, they can
also serve as stem cells. With the exceptions of blood and lymph, the connective

tissue consists of different cell types and extracellular material called matrix.
The extracellular matrix consists of protein collagen, reticular, and elastic
fibers and the ground substance within which are embedded the different
protein fibers. The ground substance has a gellike characteristic that contains a

mixture of glycoproteins and carbohydrates with a high water-binding affinity
(hydration). As a result, the highly hydrated state of the ground substance allows
for efficient exchange of nutrients, oxygen, and metabolic waste between the
cells and the blood vessels. The connective tissue also binds, anchors, and

supports various cells, tissues, and organs of the body. In addition, the
connective tissue matrix contains numerous cell types that provide essential
protection and defense against bacterial invasion and foreign bodies. The
connective tissue is classified as either loose connective tissue or dense

connective tissue, depending on the amount, type, arrangement, and abundance
of cells, fibers, and ground substance.

CLASSIFICATION OF CONNECTIVE

TISSUE

Loose Connective Tissue

Loose connective tissue is more prevalent in the body than dense connective

tissue. It is characterized by a loose, irregular arrangement of connective tissue
fibers and abundant ground substance. Various connective tissue cells and fibers
are found in the matrix. Collagen fibers, fibroblasts, fibrocytes, adipose cells,
mast cells, plasma cells, and macrophages predominate in the loose connective
tissue, with fibroblasts being the most common cell types. Figure 5.1 shows the

various types of cells and fibers that are usually found in loose connective tissue.

165