Chapter 6: Skeletal System

• Components of Skeletal System

  Bones

  Cartilages

  Tendons

  Ligaments
• Functions of Skeletal System

  1.Body support

  2. Organ protect

  3. Body movement

  4. Mineral storage

  5. Blood cell production
• Bone, cartilage, tendons, and ligaments of the skeletal system are all connective tissues.
• The matrix always contains collagen, ground substance, and other organic molecules, as well as water and minerals.
• Collagen


  is a fibrous protein that provides flexibility but resists pulling or compression.
• Matrix ground substance contains proteoglycans which are water trapping proteins that help cartilage to be smooth and resilient.
• Bone Matrix


  is about 35% organic and 65% inorganic material by weight. The organic material is primarily collagen and proteoglycans.
• hydroxyapatite


  the inorganic material in bone matrix
• Collagen fibers lend flexible strength to the bone
• The mineral component gives bone compression (weight bearing) strength.
• Osteoblasts


  are responsible for the formation of bone and the repair and remodeling of bone.
• What do osteoblasts produce?

  collagen and proteoglycans
• Ossification


  formation of new bone by osteoblasts
• Osteocytes


  are cells that maintain bone matrix and form from osteoblast after bone matrix has surrounded it.
• Osteocytes account for 90–95% of bone cells and are very long-lived
• Lacunae

  Osteocyte cell bodies are housed within the bone matrix
• Canaliculi


  Their cell extensions are housed in narrow, long spaces
• Osteoclasts


  bone-destroying cells
• Reabsorption (Osteoclasts)


  contribute to bone repair and remodeling by removing existing bone
• Bone breakdown is important for mobilizing crucial Ca2+. As bone is broken down, the Ca2+ goes into the blood.
• Lamellar Bone


  Mature bone
• Lamellae


  organized lamellar bone into thin, concentric sheets or layers
• Spongy bone consists of interconnecting rods or plates of bone called trabeculae
• Spaces in trabeculae are filled with bone marrow and blood vessels
• Compact bone


  cortical bone, is the solid, outer layer surrounding each bone
• The functional unit of compact bone is an osteon. It is composed of concentric rings of matrix surrounding a central canal
• Canaliculi


  connect osteocytes to one another, transport nutrients and remove waste
• Lamellae


  are concentric rings of bone matrix which surround the central canal
• Diaphysis


  the center portion of the bone
• Medullary cavity


  hollow center of the long bone
• Epiphyses


  contain mostly spongy bone, with an outer layer of compact bone; ends of a long bone
• Articular cartilage


  end of a long bone is covered with hyaline cartilage
• Epiphyseal plate is located between the epiphysis and the diaphysis. Growth in bone length occurs at the epiphyseal plate.
• Epiphyseal line


  When bone stops growing in length, the epiphyseal plate becomes ossified
• Bone Marrow


  Cavities in spongy bone and the medullary cavity in the diaphysis are filled with soft tissue
• Red Marrow


  is the location of blood forming cells
• Yellow marrow is mostly fat
• The outer surface of a bone is covered by a connective tissue membrane called periosteum
• The endosteum is a single cell layer of connective tissue that lines the internal surfaces of all cavities within bones; includes osteoblasts and osteoclasts
• Intramembranous ossification


  starts within embryonic connective tissue membranes; occurs when osteoblasts begin to produce bone within connective tissue; occurs primarily in the bones of the skull;