The proportion of the different types of fibers in the “ground substance” gives the connective tissue its variable characteristics.
These include protein-based fibers, whose most important function is to provide support to body structures. There are many forms of connective tissue. The protein fibers (fibres) come in three forms; collagen, elastin and reticular fibers* - the proportions of which vary depending on the function of the tissue in which they are found. Each, however, provides support and strength along with flexibility. The molecules that form the protein fibers and ground substance are secreted by specialized connective tissue cells. (*pertaining to the reticulin: A scleroprotein present in the connective fibers of reticular or lymph tissue).
Loose connective tissue includes adipose tissue, which is specialized for fat storage. One type of dense connective tissue, known as dense regular connective tissue, forms tendons and cartilage. Another, elastic connective tissue is specialized for stretching and is found in the lungs, some artery walls and the vocal chords.
The skeleton keeps the organs, blood vessels and nerves in place and, to a certain extent, affords some protection. The connective tissue supports and binds them together. It also supplies the ligaments and tendons for the joints and muscles, the tethering for the larger organs, the softness for protection and rigidity in the form of cartilage. Loose connective tissue is found through-out the organism and has a fundamental role in the nutrition of all tissues because it allows blood vessels to pass through it. Dense connective tissue is very strong and makes up tendons and ligaments. There are also other specialized types of connective tissue with specific properties, such as adipose tissue, cartilaginous tissue, bone tissue, blood tissue, and lymphoid tissue. Connective tissue is found holding the cells together within organs. The proportion of different types of fiber in the “ground substance” gives connective tissue its variable characteristics.
Areolar tissue is formed throughout the body in loose sheets around blood vessels, nerves and tendons; as a soft pliable substance it helps to fill the spaces between larger organs. The tissue is made of a mixture of collagen, elastic and reticulin fibres.This can be seen in the liver substance and in the artery wall itself; here the circular muscle is held in place by a protective sheath of loose areolar tissue. Under the skin and face it contains a large amount of mobile, elastic fibres, in contrast to the palms of the hands and soles of the feet, which are tough and contain more collagen fibres.
Collagen
Collagen is an important structural protein in the body. It is made up of chains of amino acids, with glycine, proline and hydroxyproline being the most common. Collagen is often organized in long parallel bundles of fibers, forming connective tissue, which has a very high tensile strength (for example tendons and ligaments). Collagen may also be formed into sheets (such as mesenteries of the abdominal cavity).
Fat Cells
Fat cells have three functions: Storage; insulation; protection over certain areas, such as the buttocks, and around various organs, such as the kidneys and heart and in the liver. Some of the areas of the body consist mainly of fat storage cells. Fat cells develop in infancy and then their total number remains constant for the rest of life.
Cartilage is a special form of connective tissue and supplies the fabric for the formation of bone. Cartilage is a tough, semi-transparent, elastic, flexible connective tissue consisting of cartilage cells (chondrocytes and chondroblasts) scattered through a glycoprotein material and strengthened by collagen fibers. The exterior part of cartilage is covered by dense fibrous membrane called the perichondrium. Adult cartilage does not contain blood vessels or nerves but is filled with small holes to allow nutrition to seep into it. Cartilage has several functions. It covers the surface joints, allowing bones to slide over one another, thus reducing friction and preventing damage; it also acts as a shock absorber. It forms part of the structure of the skeleton in the ribs, where it joins them to the breastbone (sternum). Cartilage is found in the tip of the nose, in the external ear, in the walls of the windpipe (trachea) and the voice box (larynx) where it provides support and maintains shape.
Cartilage comes in different forms, depending on its different physical properties.
