Classification of general connective tissue

According to Gray’s Anatomy (Williams 1995, page 88-90), the general connective tissues can be classified, in relation to their cell types and their extracellular matrix, into irregular and regular connective tissue.

The irregular tissue can be further divided into:
• Loose tissue. Loose connective tissue is ubiquitous. It forms the subcutaneous tissue of eyelids and external reproductive organs, the submucous coat in the digestive tract and the subserous tissue. It is found between muscles, vessels, nerves and interior organs. Interweaving in all directions, thin collagen and elastin fibres form the basis of this tissue. The casual-straggled arrangement of the fibres into the loose connective tissue determines elasticity and tensile stamina.
• Dense tissue. This tissue constitutes the sheaths of organs, which need protection from mechanical stresses. The extracellular matrix encloses thick bundles of collagen fibres setting in three dimensions and providing substantial strength. It is found in structures such as the reticular layer of the dermis, the sheaths of muscle and nerves and the adventitia of large blood vessels, the capsules of different glands, the coverings of diverse organs, the sclera of the eye, the periostea and the perichondria.
• Adipose tissue. This tissue looks like loose connective tissue, but it contains many more fat cells. It gathers in certain regions such as subcutaneous tissue, and around the kidneys, in the mesenteries and omenta, in the female breast, in the orbit behind the eyeball, in the marrow of bones, deep to the plantar skin of the foot, and as localized pads in many joints.

The regular connective tissue is predominantly consists of collagen fibres with some elastin fibres, which are located between them, except some ligament such as ligamenta flava, which are rich in elastic fibres. Regular connective tissue comprises tissue with regularly oriented fibres such as fasciae, aponeuroses, ligaments and tendons. The fibres in those structures are oriented towards stress forces. They keep their helical form, which enhances their mechanical features.

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