Connective Tissue

Tissue Composition

• Epithelial tissue consists mainly of cells.

Connective Tissue

• Interstitial fluid in connective tissue provides nutrients and oxygen to cells and removes waste products.
• The extracellular matrix (ECM) components include collagen fibers, elastic fibers, reticular fibers, and ground substance.
• The major component of most types of connective tissue is collagen.
• Adipose tissue is a type of connective tissue that stores energy in the form of fat.
• Nervous tissue is NOT one of the four basic tissues.

Extracellular Matrix (ECM)

• The major components of the ECM are collagen fibers, elastic fibers, reticular fibers, and ground substance.
• Collagen fibers provide strength and structure to connective tissue.
• Elastic fibers are composed of elastin and provide flexibility to connective tissue.
• Reticular fibers are composed of type III collagen and provide a supporting framework for cells.

Connective Tissue Types

• Loose connective tissue is fundamentally different from connective tissue in terms of composition.
• Connective tissue proper and specialized connective tissue provide support, connect, and surround various body structures.
• Cell types found in connective tissue include fibroblasts, adipocytes, chondrocytes, osteocytes, and hematopoietic cells.
• Delicate structures like blood vessels are surrounded by loose connective tissue.
• Connective tissue develops from mesenchyme, the precursor tissue.

Collagen Types

• Type I collagen is responsible for resistance to tension in the skin, tendon, bone, dentin, and cementum.
• Type II collagen is responsible for resistance to pressure in cartilage.
• Type III collagen, also called reticulin, is found in the skin, muscle, blood vessels, and hematopoietic organs.
• The main function of reticular fibers (type III collagen) is to provide a supporting framework for cells.
• Reticular fibers are stainable with silver stains.

Elastic Fibers

• Elastic fibers are composed of elastin and provide flexibility to connective tissue.
• Elastic fibers are most suitable for tissues that require elasticity, such as lung and skin.

Ground Substance

• The main function of the ground substance in connective tissue is to attract and hold water, creating a hydrated environment.
• Hyaluronic acid is a type of glycosaminoglycan that doesn't need a core protein.
• Proteoglycans consist of glycosaminoglycans and core proteins.
• Fibronectin is a glycoprotein present throughout connective tissue and mediates normal cell adhesion and migration.

Connective Tissue Subtypes

• Loose connective tissue provides delicate support around blood vessels.
• Reticular connective tissue forms a framework for cells in lymph nodes and spleen.
• Dense regular connective tissue provides strength and resists stretching forces in all directions.
• The main function of loose connective tissue is to provide support and connect various body structures.
• Dense regular connective tissue is commonly found in tendons and ligaments.
• Loose connective tissue has lots of cells, lots of ground substance, and a few thin collagen fibers.
• The main function of dense connective tissue is to provide strength and support to the body.
• Dense irregular connective tissue has fewer cells, less ground substance, and thick bundles of collagen fibers.