II. Bone Types

  1. Cortical Bone (80%)
    1. Outer supporting structure (Dense)
    2. Sites
      1. Radius
      2. Skull
      3. Long bones
    3. Peak density: age 30 to 40 years
  2. Trabecular Bone (20%)
    1. Inner supporting structure (Spongy)
    2. Sites
      1. Hip
      2. Spine
      3. Femur

III. Physiology

  1. Microfractures occur via everyday wear and tear
    1. Healed by ongoing bone remodeling
  2. Bone Remodeling
    1. Bone remodeling occurs in 120 day cycles
      1. Resorption by Osteoclasts over first 20 days
      2. Bone formation by Osteoblasts over last 100 days
    2. Osteoblasts
      1. Fill in bony cavity with bone matrix
      2. Triggers for activity
        1. Parathyroid Hormone
        2. Thyroxine
        3. Growth factors
          1. Interleukins (1, 6, 11)
          2. Insulin-Like Growth Factors
          3. Transforming Growth factor-B
      3. Releases Cytokines to attract Osteoclasts
    3. Osteoclasts
      1. Release proteases
        1. Dissolves bone mineral matrix
        2. Dissolves Collagen
      2. Clears away damaged bone
      3. Releases matrix-bound growth factors
        1. Chemoattractant for Osteoblasts
  3. Chemicals involved in bone formation
    1. Calcitonin
      1. Inhibits bone resorption
      2. Inhibits intestinal Calcium, Phosphorus absorption
      3. Inhibits renal Calcium excretion
      4. Inhibits calcitriol production in Kidney
    2. Calcitriol
      1. Increases intestinal Calcium absorption
      2. Increases intestinal Phosphorus absorption
      3. Increases intestinal Magnesium absorption
      4. Decreases Parathyroid Hormone secretion
    3. Parathyroid Hormone
      1. Mobilizes Calcium and Phosphorus from bone
      2. Increases Calcitriol

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Related Studies

Ontology: Osteoblasts (C0029418)

Definition (NCI) Cells which secrete an extracellular matrix into which hydroxyapaetite crystals are deposited to form bone.
Definition (MSH) Bone-forming cells which secrete an EXTRACELLULAR MATRIX. HYDROXYAPATITE crystals are then deposited into the matrix to form bone.
Definition (CSP) bone forming cells which secrete an extracellular matrix, hydroxyapatite crystals are then deposited into the matrix to form bone.
Concepts Cell (T025)
MSH D010006
SnomedCT 48156001
LNC LP96511-8
English Osteoblasts, osteoblast, osteoblasts, cells osteoblasts, cells osteoblast, Osteoblast, Osteoblast (cell)
French Ostéoblaste, Ostéoblastes
Swedish Osteoblaster
Czech osteoblasty
Finnish Osteoblastit
Latvian Osteoblasti
Polish Komórki kościotwórcze, Osteoblasty
Norwegian Osteoblaster
Spanish osteoblasto (célula), osteoblasto, Osteoblastos
German Osteoblasten
Italian Osteoblasti
Dutch Osteoblast, Osteoblasten
Portuguese Osteoblastos

Ontology: Osteoclasts (C0029431)

Definition (NCI) A large multinuclear cell associated with the absorption and removal of bone. (MeSH)
Definition (CSP) large multinuclear cell associated with the absorption and removal of bone.
Definition (MSH) A large multinuclear cell associated with the BONE RESORPTION. An odontoclast, also called cementoclast, is cytomorphologically the same as an osteoclast and is involved in CEMENTUM resorption.
Concepts Cell (T025)
MSH D010010
SnomedCT 27770000
English Osteoclasts, osteoclast, osteoclasts, Osteoclast, Osteoclast (cell)
French Ostéoclaste, Ostéoclastes
Swedish Osteoklaster
Czech osteoklasty
Finnish Osteoklastit
Japanese 溶骨細胞, 破歯細胞, 破骨細胞, 破骨器
Italian Osteoclasto, Osteoclasti
Polish Komórki kościogubne, Osteoklasty
Norwegian Osteoklast, Osteoklaster
Spanish osteoclasto (célula), osteoclasto, Osteoclastos
German Osteoklasten
Dutch Osteoclast, Osteoclasten
Portuguese Osteoclastos