noun, plural: connective tissues
The animal tissue that chiefly originates from the embryonic mesoderm, and comprised of specialized cells embedded in the matrix abundant in extracellular components (such as fibers and ground substance, which aid in the binding between, or providing structural support to, tissues or organs)
The animal body is comprised of different tissues. There are four fundamental types of animal tissues: muscle tissues, epithelial tissues, connective tissues, and nervous tissues.
The connective tissue is an animal tissue that is predominantly composed of extracellular components (such as fibers and intercellular substances). The types of fibers that form the connective tissues are collagenous fibers, elastic fibers, and reticular fibers. Some connective tissues, though, are not as fibrous, e.g. adipose tissues and blood. The cellular elements also vary from one connective tissue to another. The connective tissue cells are cellular elements of the connective tissue. They include fibroblasts, adipocytes, macrophages, mast cells, and leukocytes. The major functions of connective tissues are to connect, support, and surround tissues and organs.
In adult humans and other vertebrates, the connective tissues may be classified as either connective tissue proper or special connective tissue. Below is a list of subdivisions:
I. Connective tissue proper
A. Dense connective tissue – has more fibers than ground substance
1. Dense regular connective tissue – where (collagen) fibers are arranged in a parallel fashion, thus, appearing to be arranged in only one direction
2. Dense irregular connective tissue – where fibers are arranged in such a way that they are apparently arranged in multiple directions
B. Loose connective tissue – has more ground substance than fibers
II. Special connective tissues – includes reticular connective tissue, adipose tissue, cartilage, bone, and blood
Note: other references classify connective tissues differently. Thus, it is not uncommon to see certain connective tissue types classified differently. For instance, adipose tissue, a special connective tissue type, is classified as a loose connective tissue (under connective tissue proper).