Bones and Soft Tissue Histology
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Questions and Answers

What is the most common type of osteomyelitis?

  • Chronic osteomyelitis
  • Tuberculous osteomyelitis
  • Mycobacterial osteomyelitis
  • Pyogenic osteomyelitis (correct)
  • In which age group are benign bone-forming tumors like osteoid osteoma and osteoblastoma most common?

  • Children under 5 years old
  • Adults between 30-40 years old
  • Adolescents between 10-20 years old (correct)
  • Elderly above 60 years old
  • What is the characteristic feature of Ewing sarcoma on radiographic findings?

  • Sclerotic lesion with well-defined borders
  • Lytic lesion with sclerotic margins
  • Lytic lesion with infiltrative margins that may involve soft tissue (correct)
  • Mixed lytic and sclerotic lesion with periosteal reaction
  • What is the name of the syndrome associated with enchondromas and secondary chondrosarcomas?

    <p>Maffucci syndrome</p> Signup and view all the answers

    Which of the following is a characteristic feature of osteomyelitis?

    <p>All of the above</p> Signup and view all the answers

    What is the name of the benign tumor of hyaline cartilage that occurs in bones of endochrondral origin?

    <p>Chondroma</p> Signup and view all the answers

    What is the location of osteomyelitis in neonates?

    <p>Metaphyses and/or epiphyses</p> Signup and view all the answers

    What is the name of the malignant matrix-producing tumor of bone that commonly occurs in the axial skeleton?

    <p>Chondrosarcoma</p> Signup and view all the answers

    Which of the following describes Osteomalacia?

    <p>Abnormal mineralization of bone due to Vitamin D deficiency</p> Signup and view all the answers

    What is a key characteristic of Paget Disease?

    <p>Mosaic pattern of lamellar bone with cement lines</p> Signup and view all the answers

    What is the most common cause of Osteonecrosis?

    <p>Steriod usage and trauma</p> Signup and view all the answers

    Which of the following is a common symptom of Osteomyelitis?

    <p>Localized bone pain and inflammation</p> Signup and view all the answers

    In Paget Disease, which population is primarily affected?

    <p>Elderly adults</p> Signup and view all the answers

    What type of fracture is most likely associated with Osteonecrosis?

    <p>Pathologic fracture</p> Signup and view all the answers

    What clinical manifestation characterizes Rickets in children?

    <p>Soft, deformed bones</p> Signup and view all the answers

    What is the characteristic sign of Pyogenic Osteomyelitis?

    <p>Bacterial infection leading to necrosis</p> Signup and view all the answers

    How does hyperparathyroidism affect bone health?

    <p>Activates osteoclasts leading to increased bone resorption</p> Signup and view all the answers

    Study Notes

    Bones

    • Basic histology:
      • Matrix: extracellular component of bone composed of osteoid (Type 1 Collagen, GAGs, proteins, Osteopontin/Osteocalcin) and minerals (Calcium hydroxyapatite)
      • Cellular components: osteoblasts, osteoclasts, and osteocytes
    • Developmental disorders:
      • Dysostoses: localized disruption of migration and condensation of mesenchyme, caused by mutations in homeobox genes, cytokines, and cytokine receptors
      • Dysplasia: fibroblast growth factor 3 (FGF3) mutations leading to achondroplasia and thanatophoric dysplasia

    Skeletal Dysplasias

    • Achondroplasia:
      • Most common skeletal dysplasia and major cause of dwarfism
      • Autosomal dominant: gain-of-function mutations in FGF3 → inhibition of endochondral growth
      • Non-lethal
    • Thanatophoric dysplasia:
      • Most common lethal form of dwarfism
      • Mutations lead to more ↑ FGF3 signaling → more severe manifestations than achondroplasia
      • Usual cause of death: respiratory insufficiency (underdeveloped chest cavity)

    Metabolic Pathways

    • Osteogenesis imperfecta "brittle bone disease":
      • Most common inherited disorder of connective tissue
      • Autosomal dominant: fundamental abnormality of extreme skeletal fragility due to too little bone
      • Four major types: Type 2 is the most lethal
    • Osteopetrosis "marble bone disease":
      • Autosomal recessive: impaired osteoclast function → excessive bone formation
      • Deposited bone is woven
      • Albers-Schönberg disease: mild autosomal dominant form

    Metabolic Bone Disease

    • Osteopenia and osteoporosis:
      • Osteopenia: decreased bone mass
      • Osteoporosis: severe osteopenia, increasing the risk of fractures
      • Bone resorption exceeds formation
      • Most common forms: senile and postmenopausal
      • Hallmark: histologically normal bone, but ↓ in quantity
    • Rickets and osteomalacia:
      • Manifestations of Vitamin D deficiency
      • Abnormal mineralization of bone
      • Decreased mineral content of bone

    Hyperparathyroidism

    • Biologic effects of PTH: ↑ Ca2+ levels
    • Bone: osteoclast activation → bone resorption
    • Kidneys:
      • ↑ Ca2+ tubular reabsorption
      • ↑ PO43- excretion (PTH = Phosphate trashing hormone)
      • ↑ Vitamin D synthesis → ↑ Intestinal Ca2+ absorption and ↑ Bone Ca2+ mobilization

    Renal Osteodystrophy

    • Skeletal changes in chronic renal failure (including dialysis)
    • Osteopenia/osteoporosis
    • Osteomalacia
    • Secondary hyperparathyroidism
    • Growth retardation
    • Pathophysiology:
      • Renal tubular acidosis → Systemic acidosis → ↑ Bone demineralization and osteomalacia
      • Poor Ca2+ reabsorption + Poor PO43- excretion → ↑ PTH → ↑ Bone resorption
      • ↓ Vitamin D synthesis and dysregulation of Ca2+-PO43- homeostasis between kidney and bone

    Paget Disease (Osteitis Deformans)

    • Increased, but disordered and structurally unsound bone mass
    • Mosaic pattern of lamellar bone with cement lines “jigsaw puzzle”
    • Clinical aspects:
      • Primarily a disease of the elderly
      • Most common bones: axial skeleton, proximal femur
      • Clinically, bone pain (from microfractures or nerve compression)
      • Complications:
        • High-output failure: Pagetic bone as AV shunt
        • Most dreaded complication: osteosarcoma and fibrosarcoma

    Fracture Healing and Osteonecrosis

    • Fracture healing:
    • Osteonecrosis:
      • Most common causes: trauma, steroids
      • Morphology:
        • Medulla more commonly affected
        • Subchondral infarcts
        • Necrotic bone: empty lacunae surrounded by necrotic adipocytes
        • Saponification: Ca2+ + Fatty acids released from adipocytes
        • Deposition of new bone with remaining trabeculae as scaffolding
        • Resorption of necrotic trabeculae by osteoclasts
      • Sequelae: collapse of necrotic bone, fracture, sloughing of articular cartilage

    Osteomyelitis

    • Pyogenic osteomyelitis:
      • Route of infection: hematogenous, extension, direct implantation
      • Causative agents:
        • S. aureus (most common, 80-90%)
        • E. coli, Pseudomonas, Klebsiella (GUT infections & IV drug users)
        • H. influenzae, GBS (neonates)
        • Salmonella (sickle cell disease)
      • Location dependent on osseous vascular circulation
      • Morphology:
        • Subperiosteal abscesses
        • Draining sinuses: consequence of periosteal rupture and soft tissue abscesses
        • Sequestrum: dead bone
        • Involucrum: newly developed sleeve of bone around dead bone
      • Clinical manifestations:
        • Systemic symptoms related to infection
        • Pain over infected bone
        • Radiograph: Lytic focus with surrounding sclerosis

    Mycobacterial Osteomyelitis

    • More destructive and more resistant to control
    • Involves spine in 40% of cases (tuberculous spondylitis, Pott disease)
    • Kyphoscoliosis and neurologic manifestations (due to disc and vertebral destruction)

    Bone-Forming Tumors

    • Osteoid osteoma and osteoblastoma:
      • Benign tumors common in 10-20 years old
      • Malignant transformation is rare
      • Morphology:
        • Haphazardly interconnected trabeculae of woven bone WITH osteoblastic rimming
        • Cytologically benign cells
        • Reactive bone surrounding the lesion
    • Osteosarcoma:
      • Bimodal age incidence
        • Most occur in
      • Pelvis, Scapula, Ribs
      • Morphology:
        • Cartilage cap: hyaline cartilage (disorganized growth plate-like) covered peripherally by perichondrium
        • Underlying bone and marrow

    Cartilage-Forming Tumors

    • Chondroma:
      • Benign tumor of hyaline cartilage that occurs in bones of endochondral origin
      • Enchondroma: intramedullary
        • Most common intraosseous cartilage tumor
      • Juxtacortical: bone surface
      • Age: 20-50 years
      • Location: metaphysis of hand and foot bones
      • Associations: Ollier and Maffucci syndrome
      • Enchondromatosis: multiple enchondromas
        • Associated with secondary chondrosarcomas
    • Chondrosarcoma, conventional type:
      • Second most common malignant matrix-producing tumor of bone
      • Age: usually a disease of the elderly (>40 years)
      • Common location: axial skeleton (pelvis, shoulder, ribs)
      • Morphology: anaplastic chondrocytes with varying cellularity, atypia, and mitosis (basis for three-tier grading)
      • Grade is a prognostic factor

    Tumors of Unknown Origin

    • Ewing sarcoma:
      • Second most common group of bone sarcomas in children
      • Radiographic findings:
        • Lytic lesion with infiltrative margins that may involve soft tissue
        • Periosteal reaction: onion-skin like deposition of the reactive bone
      • Age:
      • Most common mutation: t(11;22)
      • EWSR1-FLI1 fusion gene

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    Description

    This quiz covers the basics of bone histology, including the extracellular matrix, types of bone, and markers of osteoblasts. It's a great resource for students studying anatomy and physiology.

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