Growth & Development 2

Question 1

Interstitial growth

Answer 1

• Growth of soft tissue or cartilaginous precursor
• Grwoth from all points within tissue
• Ex trunk limbs basal part of skull

Question 2

Direction Appositional (periosteum) growth

Answer 2

• Growth of bone
• Activity of cells in the periosteum leads to direct addition of new bone to surface of existing bone

Question 3

Endochondral Ossification

Answer 3

• Prenatal and postnatal
• Calcification of plate of cartilage (soft tissue) into bone at centers of ossification
  
  • chondocranium nasal capsule to foramen magnum
  • chondocranium becomes and ossification center
  • ossifies until 3 small remnants of cartilage are left interposed between large sections of bone (ethmoid sphenoid basioccipital)
  • after birth the only thing you see are these 3 cartilaginous remnants

Question 4

Sites of Endochondral Ossification

Answer 4

• Cranial base (just behind nose)
  
  • Anterior cranial base completes at age 10
    
    • affects nasomaxillary complex
    • Growth of maxilla starts early and slows down earlier than mandible
  • Posterior cranial base completes at age 20
• Mandibular condyle (secondary cartilage)

Question 5

Mandibular Condyle

Answer 5

• Layer of fibrocartilage covers the surface of mandibular condyle
• Cartilage cells proliferate, mature on surface layer
• Centers of bone ossification
• At some point all cartilage replaced by bone

Question 6

Intramembranous Ossification

Answer 6

• Cells in periosteum secrete bone matrix directly within the connective tissue without intermediate formation of cartilage

Question 7

Intramembranous Ossification Sites

Answer 7

• Cranial vault
  
  • cranial sutures between bone plates (primary)
  • Remodeling at outer and inner bone surface
• Maxilla
  
  • Posterior and superior sutures connecting maxilla to cranium
  • undergoes surface remodeling (primary) and forward displacement
  • Max and mand always forward and downward
• Mandible except condyle

Question 8

Mandible

Answer 8

• Condylar cartilage and body of mandible are develped in seperate areas and grow via seperae mechanisms
• At 4 months utero the cartilage and body fuse
• Condylar cartilage–> Endochondral ossification
• Mandibular body–> Intramembranous ossification

Question 9

Growth Site vs Growth Center

Answer 9

• Growth site
  
  • Where growth takes place
• Growth center
  
  • Where growth is being controlled

Question 10

Location of Growth

Answer 10

• Cranial sutures/synchondrosis
  
  • Synchondrosis in nasomaxillarycomplex
• Apposition and resorption of bone on bone surface
  
  • Final shape and position of nasomaxillary complex, posterior surface of mandible and anterior symphysis

Question 11

Growth

Processes and sites

Answer 11

• Endochondral ossification
  
  • Cranial base
  • Mandibular condyle
• Intramembranous ossification
  
  • Cranial vault
  • Parts of maxilla
  • Body of mandible
• Growth is a finite process

Question 12

Remodeling

Answer 12

Final reshaping of bone through apposition, resorption

Question 13

Cortical Shift

Answer 13

• Deposition of bone on the periosteal surface and resorption of bone on the endosteal surface result in relocation of bone
• Thickness of bone is unchanged is those 2 processes are in balance
• Ex Apposition of bone on endocranial surface of cranial vault, resorption of bone on lining surface of cranial vault
• Non-ossified sutures (fontanelles) present at birth, brain expands, displacement of fontanelle, bone is deposited on the sutural edges