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DSF > DSF Histo of Bone > Flashcards

DSF Histo of Bone Flashcards

1
Q

Chondrocytes

A

Cartilage cells

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2
Q

Cartilage types

A

Hyaline
Elastic
Fibrocartilage

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3
Q

Hyaline cartilage

A

Most common cartilage type, appears glassy
Found in nasal septum, tracheal rings, larynx, sternal rib ends, articular surfaces of joints
4 roles:
Provide low-friction surface
Helps lubricate synovial joints
Distributes mechanical forces to underlying bone tissue
Forms precursor of bone in developing skeleton

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4
Q

4 roles of Hyaline cartilage

A

Provide low-friction surface
Helps lubricate synovial joints
Distributes mechanical forces to underlying bone tissue
Forms precursor of bone in developing skeleton

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5
Q

Perichondrium

A 
Dense irregular fibrous tissue
Firmly attached
Cells indistinguishable from fibroblasts
Source for new chondrocytes
Does NOT cover articular cartilage
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6
Q

What is hyaline cartilage made up of? How is it made?

A

Hyaline cartilage is highly hydratedL 60-80% of net weight is intercellular water
Chondrocytes produce hyaline cartilage matrix
3 majors classes of molecule:
Type II collagen fibers
Proteoglycans (mostly GAGs)
Multi-adhesive glycoproteins

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7
Q

How are chondrocytes arranged?

A

Chondrocytes distributed either singularly or in clusters
Clusters = Isogenous groups, usually 2-4 cells
Isogenous groups represent cells that have only recently divided

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8
Q

Where is elastic cartilage found?

A

External ear, walls of external acoustic meatus, auditory tube, epiglottis of larynx

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9
Q

What is elastic cartilage made up of?

A

Has same ground substance for matrix but contains elastic fibers and elastic lamellae
Has perichondrium

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10
Q

Fibrocartilage

A

Combination of hyaline cartilage and dense regular CT
Characterized by significant quantities of both type I and II collagen fibers as well as hyaline ground substance
NO perichondrium
Histo: row-like appearance of cells
Considerably less matrix/ground substance

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11
Q

Chondrogenesis

A

Process of cartilage development
Differentiation of stellate shaped primitive mesenchymal cells to form chondroblasts (cartilage precursor cells)
2 processes -
Appositional growth: New cartilage cells derived from inner portion of the surrounding perichondrium
Interstitial growth: Mitotic division of the chondrocytes

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12
Q

Chondroblasts

A

Cartilage precursor cells

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13
Q

What is bone made up of?

A

90% collagen by weight - flexible/tensile strength
Hydroxyapatite (mineral) - compressive strength
Type I collagen = Major structural component

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14
Q

Woven bone

A 
(Immature bone)
Disorganized
Non-lamellar
Rapidly formed
More ground substance than mature bone
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15
Q

Osteoprogenitor cells

A

New bone formation
Derived from mesenchymal cells
Periosteum and endosteum contains the osteoprogenitor cells
Appear flattened/squamous w/ light staining and elongate/ovoid nuclei

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16
Q

Osteoblasts

A

Maintains ability to divide, and secretes both type I collagen and bone matrix proteins (osteoid) that later becomes calcified
Secrete mineral vesicles
Euchromatic, extensive rER, Golgi, vesicles w/ alkaline phosphatase, lipid, gap junctions
*Have receptors for PTH
Recruit and regulate osteoclasts by secreting essential GFs, CSF-1 (M-CSF) and RANKL
Histo: Cuboidal single layer of cells in apposition to forming bone

17
Q

Osteocytes

A

10-20% of osteoblasts become osteocytes
Cell volume decreases by 70%: ~50 cell processes develop, takes 3 days
Osteocytes = >90% of bone
Maintain, communicate condition to surface via gap junctions

18
Q

Osteoclasts

A

Large, multiple nuclei
Differentiate from hemopoetic progenitor cells, mature under control of RANK-RANKL signaling mech
Resoprtion Bay (Howship Lacunae)
Actin ring (“clear zone”) to attach very tightly to bone
Ruffled border
Marked acidophilia - acid used to breakdown bone

19
Q

“Coupling” b/w Bone Formation and Bone Resorption

A

Mechano-sensation and Transduction
During growth, bone formation > bone resoprtion
Adulthood, bone formation = bone resorption
Old age, bone formation < bone resorption
*Both sides controlled by many systemic and local factors - endocrines, minerals, vitamins, GFs, mechanical loading, inflammation, etc.

20
Q

2 non-exclusive mechanisms of bone growth and formation

A

Intramembranous

Endochondral

21
Q

Intramembranous Ossification

A

Occurs directly via condensations of mesenchymal cells that differentiate to osteoblasts and secrete bone matrix
True for “flat” bones of cranial vault, clavicles, anterior mandible

22
Q

Endochondral Ossification

A
  1. Mesenchymal condensation to cartilage model
  2. Chondrocyte hypertrophy
  3. Cartilage mineralizes, bone collar forms
  4. Vascular invasion, cartilage replaced by bone
23
Q

5 zones of Epiphyseal Plate

A
  • Zone of reserve cartilage*: Typical hyaline cartilage
  • Zone of proliferation*: Clusters of cells undergo mitotic division and organize into distinct columns, secrete matrix
  • Zone of hypertrophy*: Chondrocytes can increase 10X in height, driving bone elongation, Cartilage matrix becomes compressed forming linear bands b/w the columns
  • Zone of calcified cartilage*: Matrix becomes calcified and the cartilage cells begin to degenerate, Proximal chondrocytes begin to undergo apoptosis
  • Zone of resorption*: Nearest diaphysis, Capillaries and osteoprogenitor cells begin to invade the region as spear-shaped “longitudinal spicules”
24
Q

Direct bone repair

A

External fixation of the damaged site, followed by normal internal remodeling process

25
Q

Indirect bone repair

A

Usually begins as inflammatory response:

Hematoma - Granulation tissue - FIbrocartilaginous - Soft callus - Bony callus

26
Q

Perichondrium

A

Membrane covering elastic cartilage, equivalent to periosteum surrounding bone

27
Q

Does elastic cartilage calcify with age?

A

NO - b/c flexible

28
Q

Where is fibrous cartilage found?

A

High force environments - shock absorber
Intervertebral discs, pubic symphsis, articular discs or TMJ and sternoclavicular joint, menisci of knee, triangular cartilage of wrist

29
Q

Components of Ground Substance of Bone

A

Proteoglycans (GAGs and core protein)
Multi-adhesive proteins - facilitate interaction w/ matrix
Osteonectin - hydroxyapatite attachment
Osteopontin - cell to matrix attachment
Bone sialoproteins - mineralization process
BMPs (bone mineralization GFs) - able to induce differentiation of osteoblasts
Cytokines
Other GFs

DSF (18 decks)

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