Connective and supporting tissues

Supporting (skeletal) connective tissues

These include cartilage and osseous tissues that are highly specialized connective tissue types with a distinctive arrangement of intercellular substance (matrix) and cellular types. The tissues provide mechanical support and protection, build a framework for other tissues

Cartilage tissue

• contains cells of chondroblastic line (precursor cells, chondroblasts, and chondrocytes) and a lot of intercellular substance (matrix with an elevated water content and a large amount of proteoglycans, collagen type II, and elastic fibers)
• has no blood vessels of its own and exhibits a low metabolic activity; its nutrition is provided by vessels of neighboring connective tissues
• exhibits such properties as a strength and elastic stretch deformation (reversible deformation)
• is classified into hyaline, elastic and fibrous cartilage tissue depending on the matrix structure

Cartilage tissues are the principal portions of hyaline, elastic and fibrous cartilages, which also involve an outer layer called perichondrium (besides articulating cartilage)

Hyaline cartilage

• is the most common cartilage type. It constitutes the skeleton rudiments in a fetus. The cartilage is also found in anterior parts of ribs, airways (nose, larynx, trachea, and large bronchi), and articulating cartilages
• is strong and elastic due to a high content of collagen fibers (mainly collagen type II, which constitutes up to 40% of dry residue) immersed into a dense hydrated matrix
• reproduction of cells of metaphyses (cartilage growth plates) provides for elongation of tubular bones

Costal hyaline cartilage

Hyaline cartilage of joints

Elastic cartilage

• is included in cartilage structures of airways (nose, larynx, medium-sized bronchi) and auricles
• contains a large number of elastic fibers in addition to collagen type II; this is to ensure cartilage flexibility and elastic deformation potential

Elastic cartilage

Fibrous cartilage

• is found in intervertebral discs, symphyses, sites for attachment of ligaments and tendons in bones
• thick fibers prevail (90%) in the matrix. They consist of collagen type I and are oriented along the mechanical force vectors. Collagen type II fibers that are typical of other cartilage tissues are not abundant (10%)

Fibrocartilage of intervertebral disc