Connective tissue

Connective tissue" is a fibrous tissue.^[1] It is one of the four traditional classes of tissues (the others being epithelial, muscle, and nervous tissue). Connective Tissue (CT) is found throughout the body.In fact the whole framework of the skeleton and the different specialized connective tissues from the crown of the head to the toes determine the form of the body and act as an entity. CT has 3 main components; cells, fibers, and extracellular matrix, all embedded in the body fluids. Fibroblasts are the cells responsible for the production of connective tissue. The interaction of the fibers, the extracellular matrix and the water together, form the pliable connective tissue as a whole. Connective tissue makes up a variety of physical structures including, tendons and the connective framework of fibers in muscles, capsules and ligaments around joints, cartilage, bone, adipose tissue, blood and lymphatic tissue. CT is classified into three subtypes; Embryonic CT, Proper CT, and Special CT. The Proper CT subtype include dense regular CT, dense irregular CT, and loose CT. The Special CT subtype includes cartilage, bone, adipose tissue, blood, hematopoietic tissue (tissue that makes blood cells) and lymphatic tissue. and the most abundant protein in mammals, making up about 25% of the total protein content.^[2]

Functions of connective tissue

• Storage of energy
• Protection of organs
• Providing structural framework for the body
• Connection of body tissues

Fiber types and characteristics of the connective tissue

Not to be confused with muscle fibers.

Characteristics of connective tissue:

• Cells are spread through an extracellular fluid.
• Ground Substance - A clear, colorless, and viscous fluid containing glycosaminoglycans and proteoglycans to fix the bodywater and the collagen fibers in the intercellular spaces. Ground substance slows the spread of pathogens.
• Fibers. Not all types of connective tissues are fibrous though. Examples are adipose tissue and blood. Adipose tissue gives "mechanical cushioning" to our body. Although there is no dense collagen network in adipose tissue, groups of adipose cells are kept together by collagen fibers and collagen sheets in order to keep fat tissue under compression in place (for example the sole of the foot). The matrix of blood is plasma.
• Both the ground substance and proteins(fibers) create the matrix for connective tissue.

Types of connective tissue

Tissue	Purpose	Components	Location
Collagenous fibers	-	Alpha polypeptide chains	tendon, ligament, skin, cornea, cartilage, bone, blood vessels, gut, and intervertebral disc.
Elastic fibers	-	elastic microfibrill & elastin	extracellular matrix
Reticular fibers	-	-	liver, bone marrow, lymphatic organs

Disorders of connective tissue

Main article: Connective tissue disease

Various connective tissue conditions have been identified; 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 - deficient type III collagen- 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.
• Loeys-Dietz syndrome - a genetic disease related to Marfan syndrome, with an emphasis on vascular deterioration.
• Pseudoxanthoma elasticum - an autosomal recessive hereditary disease, caused by calcification and fragmentation of elastic fibres, affecting the skin, the eyes and the cardiovascular system.
• Systemic lupus erythematosus - a chronic, multisystem, inflammatory disorder of probable autoimmune etiology, occurring predominantly in young women.
• Osteogenesis imperfecta (brittle bone disease) - caused by insufficient production of good quality collagen to produce healthy, strong bones.
• Fibrodysplasia ossificans progressiva - disease of the connective tissue, caused by a defective gene which turns connective tissue into bone.
• Spontaneous pneumothorax - collapsed lung, believed to be related to subtle abnormalities in connective tissue.
• Sarcoma - a neoplastic process originating within connective tissue.
• Hemangiopericytoma - a neoplastic process

Staining of connective tissue

For microscopic viewing the majority of the connective tissue staining techniques color tissue fibers in contrasting shades. Collagen may be differentially stained by any of the following techniques:

• Van Gieson's stain
• Masson's Trichrome stain
• Mallory's Aniline Blue stain
• Azocarmine stain
• Krajian's Aniline Blue stain
• Eosin

References

1. ^ "connective tissue" at Dorland's Medical Dictionary
2. ^ Di Lullo, G. A. (2002). "Mapping the Ligand-binding Sites and Disease-associated Mutations on the Most Abundant Protein in the Human, Type I Collagen". Journal of Biological Chemistry 277 (6): 4223–31. doi:10.1074/jbc.M110709200. PMID 11704682. http://www.jbc.org/cgi/content/abstract/277/6/4223. 

External links

• connective+tissue at eMedicine Dictionary
• Encyclopaedia Britannica, Connective Tissue
• Overview at kumc.edu
• UIUC Histology Subject 230
• Connective tissue atlas at uiowa.edu