CHAPTER 6: SKELETAL SYSTEM

• Components of Skeletal System: Bones

  Cartilages, Tendons, Ligaments
• Functions of Skeletal System: Support

  Protect, Movement, Storagel, Blood cell production
• Bone, cartilage, tendons, and ligaments of the skeletal system are all connective tissues.
• characteristics of bones, ligaments, cartilage and tendons are largely determined by the composition of their extracellular matrix.
• Collagen is a tough, ropelike protein.
• The matrix always contains collagen, ground substance, and other organic molecules, as well as water and minerals.
• Proteoglycans are large molecules consisting of many polysaccharides attaching to and encircling core proteins.
• The proteoglycans form large aggregates and attract water.
• The extracellular matrix of tendons and ligaments contains large amounts of collagen fibers, making these structures very tough, like ropes or cables.
• The extracellular matrix of cartilage contains collagen and proteoglycans.
• Collagen makes cartilage tough, whereas the water-filled proteoglycans make it smooth and resilient.
• As a result, cartilage is relatively rigid, but it springs back to its original shape after being bent or slightly compressed.
• Cartilage or Bone is an excellent shock absorber.
• The extracellular matrix of bone contains collagen and minerals, including calcium and phosphate.
• The ropelike collagen fibers lend flexible strength to the bone.
• The mineral component gives bone compression (weight-bearing) strength.
• Most of the mineral in bone is in the form of calcium phosphate crystals called hydroxyapatite.
• There are four bone shape classifications: long, short, flat, and irregular.
• Long bones are longer than they are wide; examples are upper and lower limb bones.
• Short bones are approximately as wide as they are long; examples are the bones of the wrist and ankle.
• Flat bones have a relatively thin, flattened shape; examples are bones of the skull and sternum.
• Irregular bones include the vertebrae and facial bones, which have shapes that do not fit readily into the other three categories.
• Diaphysis is Shaft compact bone tissue (on outside)
• Epiphysis ends spongy bone tissue
• Articular cartilage covers epiphyses and

  reduces friction
• Epiphyseal plate is the site of growth

  between diaphysis and epiphysis.
• Medullary cavity is the center of diaphysis red or yellow marrow
• Periosteum is the membrane around

  bone’s outer surface
• Endosteum is the membrane that

  lines medullary cavity
• Bones contain cavities, such as the large medullary cavity in the diaphysis, as well as smaller cavities in the epiphyses of long bones and in the interior of other bones.
• These spaces are filled with soft tissue called marrow.
• Red marrow is the location of blood forming cells.
• Yellow marrow is mostly fat.
• In newborns most bones have blood making red bone marrow.
• In adults red marrow in the diaphysis is replaced by yellow bone marrow.
• In adults most red bone marrow is in the flat bones and the long bones of the femur and humerus.
• Location of compact bone tissue is in the outer part of diaphysis (long bones) and thinner surfaces of other bones
• Osteon is the structural unit of compact bone
• Osteon includes lamella, lacunae, canaliculus, central canal, osteocytes
• Lamella is the rings of bone matrix