0.2 Histology module 4a and 4b: connective tissue

As may be obvious from its name, one of the major functions of connective tissue is to connect tissues and organs. Unlike epithelial tissue, which is composed of cells closely packed with little or no space in between, connective tissue cells are spread out in a matrix    . The matrix plays a major role in the functioning of this tissue. The major component of the matrix is protein fibers . The rest of the matrix is usually a fluid, but it can also be mineralized and solid, as in bones. Connective tissues come in a vast variety of forms, yet they typically have in common three characteristic components: cells , matrix and protein fibers. The amount and structure of each component correlates with the function of the tissue, from the rigid ground substance in bones supporting the body to the inclusion of specialized cells; for example, a cell that destroy molecules that can make you sick.

Functions of connective tissues

Connective tissues perform many functions in the body, but most importantly, they support and connect other tissues; from the connective tissue covering that surrounds muscle cells, to the tendons that attach muscles to bones, and to the skeleton that supports the positions of the body. Protection is another major function of connective tissue, in the form of capsules and bones that protect delicate organs and, of course, the skeletal system. Specialized cells in connective tissue defend the body from microorganisms that enter the body. Transport of fluid, nutrients, waste, and hormones is ensured by specialized fluid connective tissues, such as blood and lymph. Adipose cells store surplus energy in the form of fat and contribute to the thermal insulation of the body.

The functions of connective tissue

• . Encloses and separates . Connective tissue covers each muscle separating it from the other muscles around it.
• Connects tissues . Straps of connective tissue connect muscle to bone
• Supports and moves . Bone and cartilage add strength and support to the nose and joints.
• Stores . Adipose stores fat. Bone stores minerals.
• Cushions and insulates . Adipose tissue cushions your kidneys and eyeballs, it also serves as insulate your body against heat loss.
• Transports . Blood transports many substance throughout the entire body.
• Protects . Bone protects the brain and heart.

Classification of connective tissues

The three broad categories of connective tissue are classified according to the characteristics of their matrix and the types of fibers found within the matrix ( [link] ). Connective tissue proper includes loose or areolar connective tissue and dense connective tissue    . Both tissues have a variety of cell types and protein fibers suspended in a thick liquid matrix. Dense connective tissue is reinforced by bundles of fibers that provide strength, elasticity, and protection. In loose connective tissue, the fibers are loosely organized, leaving large spaces in between. Supportive connective tissue —bone and cartilage—provide structure and strength to the body and protect soft tissues. A few distinct cell types and densely packed fibers in a matrix characterize these tissues. In bone, the matrix is rigid and described as calcified because of the deposited calcium salts. In fluid connective tissue    , in other words, lymph and blood, various specialized cells circulate in a watery fluid containing salts, nutrients, and dissolved proteins.