Of the four tissue types we have in our bodies, connective tissue is the most abundant. The other three are nervous, muscle and epithelial tissue.

Connective tissue develops from an embryonic type of tissue that is made up of undifferentiated cells known as mesoderm, and its main purpose is to give and maintain the structure of our organs.

It functions both mechanically and metabolically; it binds, supports and anchors cells and tissues, and it also makes up storage of factors that are the ones that regulate cell growth and differentiation.

It also serves as an ideal medium for the distribution of nutrients and waste products that goes between the cells and blood.

Structure and components

Connective tissue contains three components: cells, fibers and ground substance. A striking difference between connective tissue and other types of tissue found in the body is that the larger portion of it is made up of the extracellular matrix (ECM), instead of cells.

This extracellular matrix consists of a combination of several protein fibers, known as collagen, reticular and elastic, and ground substance.

The ground substance found in connective tissue is basically a network of macromolecules in a hydrophilic complex (glycosaminoglycans and proteoglycans) and glycoproteins that are the ones that help stabilize the extracellular matrix.

There are three major types of connective tissue: reticular, loose, and dense. Each of these types of connective tissue is different in the way cells are arranged, how many cells, fibers and ground substance are contained in them.

Reticular Connective Tissue

This type of connective tissue is a specialized form of tissue that is mostly made up of reticular fibers of type III collagen. The reticular cells; specialized fibroblasts are the ones that produce this type of collagen.

These fibers are also highly glycosylated and they form very delicate networks that actually support cells that are found in the reticular tissue.

This also provides a framework that is perfect for hematopoietic organs and lymphoid organs, such as the spleen, bone marrow or lymph nodes.

Loose Connective Tissue

Also known as areolar connective tissue, this is a common type of tissue that you will find surrounding structures that are often under low pressure or friction.

Epithelial tissue, small blood vessels, space between muscle, lymphatic vessels and nerve fibers are some of those structures. The components of connective tissue in this type of tissue are more or less equally divided.

It has a large number of macrophages and fibroblasts, but it also has elastic and reticular fibers, as well as collagen. It is flexible, not very resistant to stress, and well-vascularized.

Dense Connective Tissue

While it has the same components as loose connective tissue, it has fewer cells and more collagen fibers than ground substance. Depending on how these collagen fibers are placed, dense connective tissue can be regular or irregular tissue.

Dense regular connective tissue has its collagen fibers arranged in a definite pattern, having them aligned to the linear orientation of the fibroblasts. Dense irregular connective tissue has no defined pattern or orientation.

It is a resistant tissue, and it provides protection, but it is not very flexible, poorly vascularized and its repair rate is quite slow. For example tendons and ligaments.