SPECIALIZED CON. TISSUE

• Adipose tissue is connective tissue where fat-storing cells or adipocytes predominate

  
• Adipose tissue normally represents 15%-20% of body weight in men, and >20% in women
• White adipocytes can store triglycerides derived from dietary fats, lipids synthesized in the liver, and free fatty acids and glycerol synthesized by the adipocyte
• Brown adipose tissue comprises up to 5% of a newborn's body weight but smaller amounts in adults
• Brown adipose tissue is rich in mitochondria and specialized for the generation of heat, playing a part in body temperature regulation (thermogenesis)
• Cartilage is a tough, resilient type of connective tissue that structurally supports certain soft tissues and provides cushioned, low-friction surfaces in joints
• There are three major forms of cartilage: hyaline cartilage, elastic cartilage, and fibrocartilage
• Hyaline cartilage is the most common type, rich in type II collagen and aggrecan complexes with bound water
• Elastic cartilage provides flexible support for the external ear, walls of the external auditory canals, and other structures, always surrounded by perichondrium
• Fibrocartilage contains varying combinations of hyaline cartilage and dense connective tissue, providing tough, strong support at tendon insertions and in intervertebral discs
• All forms of cartilage form from embryonic mesenchyme through chondrogenesis
• Bone provides solid support for the body, protection for vital organs, a site for hematopoiesis, and serves as a repository for calcium, phosphate, and other ions
• Cells of the bone include osteoblasts, osteocytes, and osteoclasts, which are important for the constant turnover and refashioning of bone
• Bone matrix consists of inorganic material like calcium hydroxyapatite and organic material like type I collagen, proteoglycans, and glycoproteins
• Periosteum is a layer of dense connective tissue on the outer surface of bone, bound to bone matrix by bundles of fibers
• Bone resorption is the process by which osteoclasts break down bone tissue by secreting acids and enzymes that dissolve the mineral matrix of the bone

  
• Endochondral ossification is the process by which bones grow in length

  
• Woven bone is nonlamellar and characterized by a random disposition of type I collagen fibers, usually temporary and replaced in adults by lamellar bone
• Lamellar bone, found in most adults, is organized as multiple layers of calcified matrix, with lamellae organized concentrically around small central canals containing blood vessels, nerves, and endosteum
• Intramembranous ossification occurs within membranes of condensed primitive mesenchymal tissue, while endochondral ossification takes place within hyaline cartilage, forming most bones of the body
• Bone growth involves both the continuous resorption of bone tissue formed earlier and the simultaneous laying down of new bone at a rate exceeding that of bone removal
• Joints are places where bones meet, allowing movement; synarthroses have limited or no movement, while diarthroses permit free movement