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MSK! MSK! MSK! > Bone Histology > Flashcards

Bone Histology Flashcards

1
Q

What is compact bone?

A

Solid and dense
Outter most layer and surrounds spongy bone
Lamellar

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2
Q

Describe Spongy bone

A 
Cancellous or trabecular
Contains trabeculae (lattice)
Internal layer of bone
Porous 
Can be lamellar or woven
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3
Q

C/C lamellar bone and woven bone

A

L

  • mature or secondary bone
  • parallel collagen to deal with stress
  • not visible on HE
  • most adult bone

W

  • immature normally replaced by lamellar
  • characterized by loose arrangements of collagen fibers
  • lower mineral content and more cells
  • forms during fracture repair and modeling
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4
Q

What is the order of physis on a long bone

A

Epi, meta, dia(long portion), meta, epi

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5
Q

Periosteum

A
  • Dense irregular
  • covers external surface
  • doesn’t cover articular cartilage
  • anchored by perforating fibers in bone matrix
  • contains osteoblasts
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6
Q

Endosteum

A
  • inner most layer of bone
  • faces medullary cavity
  • contains osteoprogenitor cells, reticular cells, CT fibers
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7
Q

Periosteum layers

A

Dense irregular
Inner layer
- osteoprogenitor cells located next to mature bone
-cells there for injury repair
Outer layer
-rich in vasculature, fibroblasts, and collagen fibers
-sharpey’s fibers anchor to outer circumferential lamellae

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8
Q

What are the organic components of bone matrix

A

Type 1 collagen fibers
Proteoglycans
Other proteins (osteocalcin, osteopontin, osteonectin)

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9
Q

What are the inorganic components of bone matrix

A 
Calcium hydroxyapatite 
Mg
K 
Na
F
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10
Q

What are the rods of bone that make up the compact bone called?

A

Osteons

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11
Q

What direction do osteons run?

A

Parallel to shaft of bone

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12
Q

What do osteons contain?

A

Nerve, artery, and vein

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13
Q

What are the portions of the osteon canals?

A

Central canal - carries blood and nerves
Perforating canals - perpendicular connections to central canal
Canaliculi - tiny channels between lacunae that allow interactions between osteocyte

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14
Q

Concentric lamellae

A

Rings of bone around central canal

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15
Q

Outer circumferential lamellae

A

Rings of bone along periosteum

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16
Q

Inner circumferential lamellae

A

Rings of bone along endosteum

17
Q

Interstitial lamellae

A

Pieces of old osteon that result from remodeling

These fill in the gaps between osteon

18
Q

Osteoprogenitors

A

Stem cells that produce osteoblasts

Found in endosteum and periosteum

19
Q

Osteoblasts

A

Mesenchymal cells that produce osteoid (non mineralized organic matrix)

Initial and control mineralization of osteoid

20
Q

Osteocytes

A

Mature bone cells that are embedded in the bone matrix

Maintain matrix
Communicate with osteoblasts to increase deposition of bone matrix

21
Q

Osteoclasts

A

Large, multinucleated cells that are produced by the fusion of monocytes
Break down bone
Cells have ruffled borders
Remodel and resorb bone through H+ and lysosomal proteins

22
Q

Intramembranous ossification

A 
Bones develop from mesenchyme precursors (they form clumps and begin making bone)
Select bones form this way
-flat bones of skull
-some of the facial bones 
-mandible
-central part of clavicle
23
Q

Endochondral ossification

A

Begins with hyaline cartilage model

Produces most of the bones of the skeleton

24
Q

Steps of endochondral ossification

A
  1. Hyaline cartilage framework (appositional growth)
  2. Degeneration of cartilage forming trabeculae
  3. Bone collar forms in the metaphysis area of later bone and develops the perichondrium
  4. Vascular and mesenchymal cells invade trabeculae and produces primary ossification center
    - this contains BM cells and osteoblasts
    - osteoid is deposited and calcifies into woven bone
  5. Epiphyses have continued growth
    - secondary ossification centers form in epiphyses
  6. Bone replaces cartilage in diaphysis
  7. Ossification centers gradually become separated by epiphyseal plate for continued elongation
25
Q

Zones of endochondral ossification

A
  1. Reserve zone
    - primitive hyaline cartilage; responsible for lengthening
  2. Proliferative zone
    - chondrocytes cluster parallel to growth axis
    - share territorial matrix
  3. Hypertrophic zone
    - chondrocyte apoptosis
    - attract vasculature
    - instruct bone collar
  4. Vascular invasion zone
    - vasculature penetrates calcified matrix
    - invasion of osteoprogenitors
26
Q

Bone remodeling has what steps

A

Activation, resorption, reversal, formation

27
Q

How is a bone fracture repaired

A

Clean-up
-clotted blood is removed by macrophage and osteoclasts resorb damaged matrix

Plug
-periosteum and endosteum produce soft callus surrounding fracture

Replace
-replace the soft callus with a hard callus

Bone
-immature, woven bone eventually replaced by lamellar bone

28
Q

Achondroplasia

A
  • autosomal dominant syndrome
  • mutation in FGFR3
  • most common dwarfism
  • shortening of long bones
  • small midface
  • altered spinal curvature
29
Q

Osteomalcia

A

-progressive shortening and bending of bone
-defect resulting in decreased mineralization of osteoid
-caused by:
Dietary vit d def
Lack of sun exposure
Gastrointestinal disease (US)
Signs and symptoms
Bone and joint pain
Muscle weakness
Fracture
Difficulty walking and waddling gait
Muscle spasms and cramps

30
Q

Rickets

A

-defect in mineralization of cartilage in growth plates
-vitamin d def, decreased abs of Ca and P from bowels
Signs:
-delayed closure of fontanelles
-parietal and frontal bone bossing
-craniotabes (soft skull bones)
-widening of the wrist and bowing of the distal radius and ulna
-progressive lateral bowing of the femur and tibia

31
Q

Osteoporosis

A
  • decrease in bone mass and increased fragility
    • loses ability to produce matrix (mostly collagen)
    • loses Ca and other bone salts
  • commonly occurs in elderly and postmenopausal females
  • no clinical manifestations until there is a fracture

MSK! MSK! MSK! (15 decks)

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