skeletal (sir tamonan)

• The skeletal system has four components: 


  bones, cartilage, tendons, and ligaments
• Bones are organs composed of 


  nerve tissue and vascular tissue
• The matrix of cartilage contains collagen fibers for strength and proteoglycans to trap water
• Bone Cells:

  • Osteoblasts - produce bone matrix / become osteocytes / from osteochondral progenitor cells
  • Osteocytes - located in lacunae / connected to one another through canaliculi
  • Osteoclasts - break down bone / from stem cells in red bone marrow
• Bone can be classified according to the amount of bone matrix relative to the amount of space present within the bone:

  • Cancellous bone has many spaces filled with red or yellow bone marrow
  • Compact bone is dense with few spaces
• Individual bones are classified according to their shape:

  • Long bones are longer than they are wide and include most bones of the upper and lower limbs
  • Short bones are about as wide as they are long and include bones of the wrist and ankle
  • Flat bones are relatively thin, flattened, and usually curved, including certain bones of the skull, ribs, sternum, and scapulae
  • Irregular bones do not fit into the other categories and include vertebrae, pelvic girdle, and facial bones
• Bone membranes:

  • Periosteum is a double layer of protective membrane covering the outer surface of bone
  • Endosteum is a delicate membrane covering internal surfaces of bone
• Bone development begins at week 8 of embryo development:

  • Intramembranous ossification: bone develops from a fibrous membrane
  • Endochondral ossification: bone forms by replacing hyaline cartilage
• Bone fractures are classified by the position of the bone ends after fracture, the completeness of the break, the orientation of the bone to the long axis, and whether or not the bone ends penetrate the skin
• • Excess material is removed, and compact bone is laid down to reconstruct shaft walls
• Bone repair process:

  1. Hematoma formation

  • Torn blood vessels hemorrhage, leading to the formation of a mass of clotted blood (hematoma) at the fracture site

  2. Callus formation

  • Granulation tissue forms, capillaries grow into the tissue, and phagocytic cells begin cleaning debris
  • Osteoblasts and fibroblasts migrate to the fracture, secrete collagen fibers, and begin forming woven bone

  3. Callus ossification

  • The fibers and cartilage of the calluses are ossified to produce woven, cancellous bone

  4. Bone remodeling
• functions of bones

  s - support

  p - protection

  m - movement

  s - storage (calcium and phosphorus)

  b - blood cell production (hematopoiesis)
• chondroblasts produce cartilage and become


  chondrocytes
• lacunae


  where chondrocytes are found
• cartilage grows by

  appositional and interstitial growth
• Bone tissue is classified as either

  woven - remodeled to form lamellar bone / collagen fibers oriented in many different directions

  lamellar - mature bone arranged in thin layers (lamellae) / collagen fibers oriented parallel to one another
• cancellous bones


  
  

  has many spaces / honeycomb of traneculae
• compact bones


  dense w few spaces
• long bones


  longer than they are wide / mostly of the limbs
• short bones 


  as wide as they are long / carpals and ankle
• flat bones


  thin, flattened, curved / skull, ribs, sternum, scapula
• irregular bones

  do not fit into the LSF category / vertebrae, pelvic girdle, facial bones