Connective tissue

Connective tissue is any type of biological tissue with an extensive extracellular matrix and often serves to support, bind together, and protect organs. There are four basic types:

• Bone contains specialized cells called osteocytes embedded in a mineralized extracellular matrix, and functions for general support.
• Blood functions in transport. Its extracellular matrix is the blood plasma, which transports dissolved nutrients, hormones, and carbon dioxide in the form of bicarbonate. The main cellular component is red blood cells.
• Cartilage makes up virtually the entire skeleton in the osteichthyes. In most other vertebrates, it is found primarily in joints, where it provides cushioning. The extracellular matrix of cartilage is composed primarily of collagen.
• Connective tissue proper
  • Dense connective tissue or Fibrous connective tissue forms ligaments and tendons. Its densely packed collagen fibers have great tensile strength.
  • Loose connective tissue or Areolar connective tissue holds organs and epithelia in place, and has a variety of proteinaceous fibers, including collagen and elastin. It is also important in inflammation.
  • Reticular connective tissue is a network of reticular fibers (fine collagen) that form a soft skeleton to support the lymphoid organs (lymph nodes, bone marrow, and spleen.)
  • Adipose tissue contains adipocytes, used for cushioning, insulation, lubrication (primarily in the pericardium) and energy storage.

Disorders of connective tissue

Various connective tissue conditions have been described, these can be both inherited and environmental.

• Marfan syndrome - a genetic disease causing abnormal fibrillin.
• Scurvy - caused by a dietary deficiency in vitamin C, leading to abnormal collagen.
• Ehlers-Danlos syndrome - a genetic disease causing progressive deterioration of collagens, with different EDS types affecting different sites in the body, such as joints, heart valves, organ walls, arterial walls, etc.
• Osteogenesis imperfecta (brittle bone disease) - caused by insufficient production of good quality collagen to produce healthy, strong bones.

See aalso: zootomy