Answer
One simple three-fold division of connective tissue is (1) fibrous connective tissues, (2) supportive connective tissues and (3) fluid connective tissues.
Fibrous connective tissues comprises loose fibrous connective tissues and dense fibrous connective tissue. The supportive connective tissue class includes cartilage and bone. The fluid connective tissue group is composed of blood and lymph.
All connective tissue are composed of cells and matrix.
The cells are mainly fibroblasts or modified fibroblasts ; other cells include macrophages/monocytes, mast cells, plasma cells leukocytes and adipocytes.
The matrix is the extracellular/intercellular substance; it is composed of ground substances and fibers but may vary in physical presentation from liquid ( in lymph and blood) to hard mineralized solid in bone.
The organic part of the ground substance is composed of glycosaminoglycan, proteoglycans and proteins..
Fibers of the matrix are usually divided into three classes --collagen, fibers, reticular fibers and reticular fibers: collagen fibers are made of type I collagen and are the largest and strongest. Reticular fibers are thinner and usually form networks that fill up space and support organs ( spleen, liver, pancreas) . Elastic fibers have special properties that enable them to recoil after being stretched,; this kind of tissue is important in lungs, urinary bladder and skin.
Work Step by Step
Loose fibrous connective tissue has a viscous or jelly-like ground substance. The fibers in this type tissue are mainly collagen and elastic fibers. Loose connective tissue is well-vascularized and its extracellular fluid is an important means of supplying nutrients to and removing wastes from the skin. Loose connective tissue is also found in the organs of the digestive tract, the respiratory tract, and the reproductive system.
In dense fibrous connective tissue the collagen fibers are packed closely together and the fibroblasts exist in irregular spaces between large Type I collagen fibers. This is the type of connective tissue in tendons and ligaments.
Cartilage and bone are classified as supportive connective tissue; there are three types of cartilage --fibrocartilage, hyaline cartilage and and elastic cartilage:
Fibrocartilage has strong collagen fibers in the matrix; this type is the cartilage of the intervertebral discs
and the knee joint. It is able to withstand great pressure.
Elastic cartilage has both collagen and elastic fibers ( more elastic than collage) ; it is found in the pinna of the ear, the epiglottis and the larynx.
Hyaline cartilage has fine collagen fibers and a ground substance that is clear or translucent. It is found at the ventral ends of ribs, at the ends of long bones, and in the rings of the trachea and bronchi. It is the cartilage of early embryos.
Bone is connective tissue with a rigid mineralized matrix. Osteoblasts form the protein part of the ground substance which becomes heavily mineralized with inorganic salts ( mainly calcium and phosphate --hydroxyapatite) which are deposited around collagen fibers.
In the fluid connective tissues--blood and lymph-- cells are suspended in liquid ground substances. These tissues are devoid of fibers but have dissolved substances such as proteins and salts. The cells of blood are leukocytes, plasma cells, erythrocytes and thrombocytes ( cell fragments). Plasma is about 90% water. The plasma proteins include albumins, globulins (gamma-globulins) and fibrinogen. Inorganic salts of calcium, potassium and sodium are dissolve in the fluid ground substance of blood and lymph.
Lymph is has a higher aqueous content than blood and serves an immune function ; it also returns fluid to the blood system to maintain cardiac output and blood pressure.
Lymph has mainly white blood cells .
