Bone Formation, Growth And Repair Flashcards

1
Q

What is osteogenesis and the 2 types

A

-bone formation

1 intramembranous
2 endochondral

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2
Q

What types of bone are made by intramembranous

A
  • flat bones of the skull

- the clavicle

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3
Q

What type of bones are made by endochondral

A

-most bones in the body including long bones

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4
Q

Describe intramembranous ossification

A
  • starts in condensed sheets of embryonic CT
  • ossification center forms and osteoblasts secrete and calcify osteoid into woven bone
  • the centers enlarge and fuse forming larger woven bone
  • later remolded into lamellae enclosing cancellous bone
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5
Q

What is an ossification center , why due they continue growing In intramembranous and what happens to none ossification center forming bones

A
  • areas where mesenchymal cells proliferate and differentiate into osteoblasts
  • due to continuous secretion of osteoid
  • become periosteum and endosteum
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6
Q

Endochondral ossification describe pre-natal

A
  • begin in hyaline shaped model
  • bone collar forms in perichondrium which is transitioning to periosteum which impedes diffusion of nutrients and chondrocytes swell up and eventually die
  • space left is invaded by capillaries and progenitor form periosteum
  • progenitor diff and make 1• ossification center at center of diaphysis
  • bone later remodeled as lamellae
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7
Q

Endochondral ossification describe around birth

A

-2• ossification center develops at epiphysis

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8
Q

What separates ossification centers during birth and describe it

A

-epiphyseal plate which is cartilage not replaced by bone

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9
Q

Purpose of epiphyseal plate

A

-longitudinal bone growth

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10
Q

What is epiphyseal line

A

-remnant of plate when bone reaches full stature

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11
Q

Where doesn’t bone replaces cartilage

A

-articulate cartilage and epiphyseal plate

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12
Q

How do the chondroblasts die and when does 1• ossification center form

A

-due to lack of nutrients

/1st trimester ( 12 months of development )

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13
Q

The zones of epiphyseal

A
Zone of resting ( farther from diaphysis of 1• ossification center )
2 proliferation zone 
3 Zone or hypertrophy
4 Zone of calcified cartilage 
5 zone of ossification
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14
Q

Describe first 2 zones of epiphyseal

A

1 has typical hyaline cartilage

2 cartilage cells divide and secrete collagen 2 and ground substance
-matrix now organized parallel to diaphysis

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15
Q

Describe the 3rd and 4th zone of epiphyseal

A
  • chondrocytes swell up due to presence of periosteum and they secrete collagen X to stiffen matrix
  • also release growth factors

-chondrocytes secrete calcium hydroxyapatite and calcify matrix then die by apoptosis

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16
Q

Describe the zone of ossification

A
  • progenitor and capillaries invade space left by dead chondrocytes
  • settle on calcified matrix and secrete osteoid - woven - lamellae
17
Q

Function of collagen X and growth factors

A
  • stiffens matrix
  • reduces diffusion of metabolites further and caused chondrocytes to die

-promote vasculature to enter from diaphysis

18
Q

Why doesn’t thickness of epiphyseal change

A

-rate of destruction and proliferation are equal

19
Q

Describe appositional growth

A
  • increase in thickness of bone
  • cells of perichondrium of cartilage proliferate and differentiate into osteoblasts
  • secrete seems at the edge of bone increasing thickness
20
Q

What accompanies appositional growth

A

-resorption of endostenum and growth of medullary cavity

21
Q

What is a hematoma

A

-localized bleeding outside of vessels due to trauma or disease

22
Q

Describe metabolic role of bone

A
  • calcium reservoir

- blood formation

23
Q

Describe bone repair of fracture

A
  • torn vessels release blood which clots forming a fracture hematoma
  • hematoma removed by macrophages and replaced by soft fibrocartilage( soft callus )
  • blood vessels invade soft callus and osteoblasts
  • cells secrete osteoid which calcifies into woven bone
  • woven remodeled into lamellae continuous with uninjured area. Vasculature reestablished
24
Q

Where does periosteum regain continuity after fracture

A

-at soft callus