8.12:
Introduction to Connective Tissues
In the human embryo, the mesoderm—one of the three germinal layers, is the source of all connective tissues.
Connective tissues perform diverse functions, from connecting and supporting other tissues to transporting solutes, including nutrients and gases.
All connective tissues have two components— the non-living extracellular matrix, composed of a gel-like ground substance and protein fibers, and the cells.
In contrast to epithelial tissues, the extracellular matrix forms the bulk of connective tissues.
Additionally, while epithelial tissues are avascular, most connective tissues, except the cartilage, are highly vascular.
Connective tissues, such as in the dermis, also contain sensory receptors to detect stimuli such as pain, pressure, and temperature.
Depending on the properties of the matrix and the cell types present, connective tissues can have different physical characteristics. For instance, bone is a hard connective tissue, while blood is fluid.
8.12:
Introduction to Connective Tissues
Connective tissues are one of the four main tissue types in humans that are extensively present in the body. They are characterized by cells embedded in an extracellular matrix (ECM) composed of a ground substance and three main types of protein fibers— collagen, elastic, and reticular fibers. The ground substance of connective tissues can range from a watery and jelly-like consistency to mineralized and hard. The wide variety of cells in the connective tissues include fibroblasts, osteocytes, adipocytes, macrophages, and many more.
As the name suggests, the primary function of connective tissue is to link different tissue types in the body. It mainly acts as a cementing and packaging material that forms the structural framework of the body. Further, some connective tissues facilitate nutrient storage and transport in the body.
Diseases of Connective Tissues
There are over two hundred diseases associated with connective tissues in different organ systems. A few examples of these diseases are listed below:
- • Rheumatoid arthritis is an autoimmune disease that affects the connective tissue in the synovial membrane of joints, leading to inflamed and deformed joints.
- • Systemic scleroderma is another autoimmune disorder characterized by the thickening and hardening of the connective tissue in the skin and blood vessels.
- • Osteogenesis imperfecta is a genetic disorder present from birth, resulting in brittle bones.
- • Dermatomyositis is an inflammatory disease associated with connective tissues that results in gradual skin changes and muscle weakness. It may have unknown genetic causes that trigger an autoimmune response. Environmental factors like viral infections, sun exposure, smoking, and certain medications could aggravate symptoms.