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Bone PhysiologyAka: Osteoblast, Osteoclast, Cortical Bone, Trabecular Bone

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  1. See Also
    1. Bone Densitometry
    2. Bone Turnover Biochemical Marker
    3. Osteoporosis
    4. Paget's Disease of Bone
  2. 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
  3. 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
  4. References
    1. Rosen (1998) Postgrad Med 104(4):101

Osteoblasts (C0029418)

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.
Definition (NCI)Cells which secrete an extracellular matrix into which hydroxyapaetite crystals are deposited to form bone.
ConceptsCell (T025)
MSHD010006
EnglishOsteoblast, Osteoblasts
Spanishosteoblasto
Parent ConceptsCell of bone (C0222677), Connective Tissue Cells (C0009781)
SourcesAOD, CSP, MSH, NCI, SCTSPA, SNOMEDCT, UWDA
Derived from the NIH UMLS (Unified Medical Language System)


Osteoclasts (C0029431)

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.
Definition (CSP)large multinuclear cell associated with the absorption and removal of bone.
Definition (NCI)A large multinuclear cell associated with the absorption and removal of bone. (MeSH)
ConceptsCell (T025)
MSHD010010
EnglishOsteoclast, Osteoclasts
Spanishosteoclasto
Parent ConceptsCell of bone (C0222677), Connective Tissue Cells (C0009781), macrophage (C0024432), Phagocytes (C0031307), Mononuclear phagocyte system (C1267793)
SourcesAOD, CSP, MSH, NCI, SCTSPA, SNOMEDCT, UWDA
Derived from the NIH UMLS (Unified Medical Language System)



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