Limb and bone development Flashcards
What is the primary ossification center?
Diaphysis
What is the secondary ossification center?
Epiphysis
What are the two types of ossification?
Endochondral ossification - cartilaginous
Intramembranous - fibrous membrane
What is appositional bone growth?
New chondroblast add new layers increasing diameter
What is interstitial bone growth?
Chondrocytes lay down more matrix in cartilage increasing length - epiphyseal plates
What are the stages of intramembranous ossification?
From mesenchyme - condense
Vascularize and differentiate into osteoblasts
Collagen fibers lay
Early osteoblast cluster - center for ossification
What are the stages of calcification?
Osteoblasts secrete osteoid
Cells surrounded by matrix form lacunae
Osteoblast secrete alkaline phosphatase with calcifies osteoid
What is cancellous bone?
Inner bone layer
What is compact bone?
Outer bone layer
What are the steps of endochondral ossification?
Mesenchyme condenses and differentiates into chondroblasts with form cartilage. Chondrocyte matures, calcifies, and dies
Growth to form periosteum
Mesenchymal cells to osteoprogenitors to osteoblasts
Form endosteum
What are the 5 zones of the epiphyseal plate?
Reserve cartilage
Cell proliferation
Cell maturation and hypertrophy
Calcifying cartilage
Provisional ossification
What are the types of epiphysis?
Pressure
Traction
Atavistic
Aberrant
What are the arteries to bone?
Nutrient
Periosteal
Metaphysial
Epiphysial
What are the nonartery vessels and nerves that go to bone?
Nutrient vein
Lymphatic vessels in periosteum
Periosteal nerves
What causes achondroplasia?
Early ossification of epiphyseal plate
What are the 4 stages of limb development?
Bud
Paddle
Plate
Rotation
What forms a limb bud?
Outer ectodermal cap
Inner mesodermal core
What is the role of apical ectodermal ridge?
Digit formation and elongation of limb segments
What maintains apical ectodermal ridge?
Zone of polarizing activity mediated by SHH
What occurs in the absence of apical ectodermal ridge?
No limb development
What is responsible for the positioning of limbs during development?
HOX genes
What is necessary to initiate limb development?
fgf signalling
When does amelia occur?
Suppression of limb bud in early wk 4?
When does meromelia occur?
Disturbance in differentiation in wk 5
What is brachydactyly and its cause?
Shortness of digits
Autosomal dominant
What multipotent stem cells are derived by somites?
Sclerotome
Myotome
Dermatome
What is derived by somatic lateral mesoderm?
Sternum, limbs, and girdles
What is derived by sclerotome of paraxial mesoderm?
Vertebrae and ribs
