Skeletal System

1
Skeletal System
2
Endochondral Ossification

• inside cartilage
• Form within hyaline cartilage
• Cartilage framework for organized ossification
• 6 wks thru 25 yrs
• Growth pattern of long bones

3
Fetal Bone Development
4
Infant to 25 yrsLong Bone Epiphyseal Plate
5
Endochondral Ossification
6
(No Transcript)
7
Endochondral Ossification

• Cartilage model develops
• Cartilage grows
• Medullary cavity forms
• Primary ossification center forms
• Secondary ossification center forms

8
Endochondral Ossification

• Mesenchymal model forms during development
• Mesenchymal differentiate into chondroblasts at
  center of growing cartilage
• Chondroblasts grow (hypertrophy) enlarged lacunae
  create reduce matrix to thin struts that calcify
• Vascularization of cartilage
• Perichondrium cells convert to osteoblasts
• Blood vessels penetrate cartilage bringing blood
  supply osteoblasts
• Oteoblasts produce spongy bone
• Remodelling of spongy bone to compact bone

9
Mesenchyme Cells form Bone Model
10
Mesenchyme Cells Differentiate to Chondroblasts
Chondroblasts Convert tissue to Cartilage
11
Perichondrium Develops Around Cartilage Model
12
Cartilage Grows in Length Girth
Length Growth is Called interstitial growth
Width Growth is Called appositional growth
13
Endochondral Ossification

• Cartilage framework initial step
• As cartilage grows (hypertrophy) centrally
  located chondrocytes rupture
• Begins ossification of cartilage
• At margins cartilage model continues to grow
• Proliferation vs hypertrophy

14
Proliferation vs Hypertrophy
Center
Edges
15
Cartilage Continues to Grow
16
Hypertrophied Cells Burst Stimulating
Calcification of Matrix
17
Hypertrophied Cells Burst Stimulating
Calcification of Matrix
18
Osteoblast Produce Bone Collar
Vascularization Stimulates Mesenchymal Cells to
Convert to Osteoblasts
19
Perichondrium Converts to Periosteum
20
Vascularization of Tissue Carries Osteoblast into
Matrix Forming Primary Ossification Center
21
Primary Ossification Center
22
Primary Ossification Center Continues to Grow at
Edges
Ossification begins in diaphysis migrates
toward the epiphysis
23
Cartilage Continues to Grow Ossification
Continues towards ends of Diaphysis
24
Cartilage Continues Proliferation Hypertophy
25
Ossification of Cartilage Continues Towards ends
of shaft
Center
Ends
26
Calcified Cartilage Matrix
27
Forms Spongy Bone
28
Form Trabeculae of Spongy Bone
29
Osteoclast Remodel Spongy Bone to Compact
30
Bone Remodeling
31
Bone Remodeling Forms Medullary Cavity
32
Forms Haversian System
33
Endochondral Ossification

• Blood vessels osteoblasts migrate into
  epiphysis
• Secondary ossification centers
• Bone ossification remains incomplete
• Epiphyseal plate
• Site of continued bone growth
• Produces VERY structured compact bone

34
Blood Vessels Enter into Diaphysis
35
Secondary Ossification Centers Form
Ossification of epiphysis
36
Secondary Ossification Centers
37
Cartilage at Edges Persists as Articular Cartilage
38
Metaphysis

• Location- epiphyseal plate
• Site of bone elongation
• Growing cartilage plate persists
• Zone of proliferation
• Zone of Hypertrophy

39
Epiphyseal Plate
40
Long Bone Elongation
41
Bone Elongation

• Chondrocytes divide and produce new cartilage
• Diaphysis- chondrocytes replaced by invading
  osteoblasts
• During growth stage chondrocyte activity matches
  osteocyte activity
• At maturation osteocyte invasion is FASTER than
  chondrocyte division
• Puberty- Sex hormones stimulate osteoblast
  chondrocyte activity aka growth spurt

42
Chondrocyte Proliferation
43
Osteocyte Invasion
44
(No Transcript)
45
(No Transcript)
46
Bone Growth Disorders

• Achondroplastic dwarf
• Results from slow epiphyseal plate growth early
  plate closure
• Chondrocytes have slower activity
• Results in normal trunk growth stunted long
  bone growth

47
(No Transcript)
48
(No Transcript)
49
Bone Growth Disorders

• Marfans syndrome
• Dominant genetic disorder
• Abnormal connective tissue growth
• Hyperactive chondrocytes epiphyseal plate
• Symptoms- long thin limbs

50
(No Transcript)