SKELE-MIDTERM

• 99% of body's calcium is stored in bones, 85% of body's phosphorus is stored in bones
• Formation of Bony Skeleton


  1. Before week 8: Embryonic skeleton made of fibrous membranes and hyaline cartilage

  2. After week 8: Bone tissue begins to replace the fibrous membranes and hyaline cartilage via Intramembranous Ossification or Endochondral Ossification
• Endochondral or Intrachondral Ossification


  Cartilaginous model (hyaline cartilage) replaced by bones - "Indirect transformation"
• Classification of Bones According to Origin

  • Intramembranous Ossification
  • Endochondral Ossification
• Classification of Bones According to Structure

  • Compact bone
  • Spongy bone

  
• Spongy bone


  Also known as cancellous or trabecular bone, has honeycomb appearance with cavities/air spaces, located mainly in the epiphyses of long bones and the interior of all other bones, consists of a branching network of trabeculae with bone marrow

  
• Long bones


  Much longer than they are wider, e.g. humerus, femur, clavicle, radius, ulna, metacarpals, metatarsals, phalanges

  
• Short bones


  Length is almost same as width, cuboidal, e.g. bones of the wrist, ankle, carpals, and tarsals

  
• Irregular bones


  Unclassified bones, e.g. vertebrae, pelvic bone

  
• Classification of Joints Based on Function (Degree of Movement)

  • Diarthroses (freely movable)
  • Amphiarthroses (slightly movable)
  • Synarthroses (immovable)
• Amphiarthroses


  Slightly movable, e.g. Vertebral Disc, Costosternal Joints, Pubic Symphysis
• Hinge joints


  Articulating surface: resembles door hinges, e.g. Elbow joint, knee joint, ankle joint
• Gomphoses


  Binds teeth to bony sockets in the maxillae and mandible, linked by periodontal ligament

  
• Fetal Skull


  Compared to adult, has disproportionately large cranium relative to the face, bones are smooth and unilaminar, most bones are ossified at birth but the process is incomplete, bones are mobile on each other

  
• Fontanelle


  Separates the bones of the vault that are not closely knit at the sutures. At these sites, the sutures form wide areas of fibrous tissue.

  
• Anterior fontanelle


  Most prominent; "soft spot"; lies between, the frontal bone and the two parietal bones behind; Diamond-shaped; By 18 mos. The surrounding bones have fused and the anterior fontanelle is no longer clinically palpable.
• Posterior fontanelle


  Bounded by the parietal bones anteriorly and the occipital bone posteriorly; Triangular shape; begins to close during the first few months after birth, and by the end of the 1st year, it is small and no longer clinically palpable.
• Middle cranial fossa


  • "Butterfly-shaped" with a central part composed of the sella turcica (saddle-like bony formation on the upper surface of the body of the sphenoid that houses the pituitary gland)
  • Contains the temporal lobes
  • WEAKEST – because it has many foramina
  • Fracture: otorrhea
• Posterior cranial fossa


  • Bones: Occipital and Temporal (O-T ka sa likod)
  • Contains the hindbrain: cerebellum, pons, medulla
  • LARGEST

  
• Endochondral Formation


  1. Development of the cartilage model

  2. Growth of the cartilage model

  3. Development of the primary ossification center

  4. Development of the medullary cavity

  5. Development of the secondary ossification centers

  6. Formation of articular cartilage and the epiphyseal (growth) plate

  
• Examples of irregular bones

  • Sphenoid
  • Ethmoid
  • Vertebral column
  • Pelvic bone
  • Sacrum
  • Coccyx

  
• There are 360 joints that connect the bones
• Examples of synarthroses (fibrous joints)

  • Sutures of the skull
  • Mental symphysis
  • Teeth in the socket
  • 1st Costosternal joint

  
• Examples of ellipsoid joints

  • Wrist joint
• Examples of gomphoses


  • Teeth joints
• Symphyses


  Bones united by fibrocartilage

  
• There are 8 bones in the cranium

  
• Bones in anterior cranial fossa

  • Frontal
  • Ethmoid
  • Sphenoid

  
• The posterior cranial fossa contains the hindbrain: cerebellum, pons, medulla