Anatomy and Physiology: Tissues
Connective tissues have the following distinct characteristics:
- Connective tissues have variations in their blood supply. Some connective tissues are poor blood supply such as the tendons and ligaments while the other have no blood supply at all (avascular) such as the cartilage. However, most connective tissues have a good blood supply (vascular).
- All structures of a connective tissue heal very slowly.
- It is composed of an extracellular matrix that enables the connective tissue form a soft packing tissue around other organs allowing the tissues to bear weight and to withstand stretching and other abuses such as abrasion that no other tissue could have endured. This makes connective tissue different from other tissues in the body.
Types of connective tissue:
- Bone – this is the most rigid connective tissue in the body which is also called osseous tissue. It is composed of lacunae which are bone cells that are sitting in cavities. The lacunae are then surrounded by layers of a very hard matrix that is comprised of calcium salts plus the large amount of collagen fibers. The bone has an outstanding ability to protect and support other body organs because of its rocklike hardness.
- Cartilage – next to the bone, cartilage is less hard but is more flexible. Though found in only few areas of the body the most widespread is the hyaline cartilage which contains a large amount of collagen fibers. The cartilage is the one that forms the supporting structures of the larynx. Aside from that it is the one responsible for attaching the ribs to the breastbone and covers the ends of the bones where they form the joints. The fibrocartilage is the cushion-like discs that are located in between the vertebrae. Another type of cartilage is the elastic cartilage that supports the external ear and is located in areas where elasticity is desired.
- Dense Connective tissue – this connective tissue forms the tendons and the ligaments. It is also called dense fibrous tissue where its main matrix is the collagen fibers. In the collagen fibers are the fibroblasts that produce the building elements of the fibers. Tendons are responsible for attaching muscles to the bone whilst ligaments are responsible for connecting bones to bone joints. Aside from tendons and ligaments, dense connective tissue makes up the dermis which is the lower layer of the skin.
- Loose connective tissue – these are softer tissues containing more cells and fewer fiber. Areolar tissue is under this type which is the most widespread tissue of its kind. Adipose tissues also called fat is an areolar tissue where fat cells are predominating. Reticular connective tissues resemble fibroblasts which form the stroma that supports many free blood cells in the lymphoid organs in the body such as the lymph nodes, spleen and the bone marrow.