Musculoskeletal Development Flashcards
What mesenchyme is the vertebral column, ribs, and sternum originated from?
Mesodermal sclerotomes
Where do the limb bones and girdles originate from?
Lateral plate mesoderm
Where does the skull and base of skull develop from?
Head mesoderm
Where do the facial bones develop from?
Neural crest
Describe the common pathway for bone/cartilage.
Mesenchyme is induced to enter and the production of N cadherins promote mesenchymal cell condensation. TGF-B stimulates synthesis of fibronectin and N-CAM. Aggregated state of mesenchymal cell is stabilized.
Membranous bone pathway?
Requires transcription factors Runx-2 and Osx, mesenchymal cells differentiate into osteoblasts
Permanent cartilage pathway?
Mesenchymal condensation forms chondroblasts and Sox-9 causes chondroblasts to secrete collagen II and cartilage matrix. Sox-9 is continually expressed in permanent cartilage.
Endochondral bone pathway formation?
TF Runx-2, genes ihh and BMP-6 induce cartilage to undergo hypertrophy. Hypertrophic cells secrete bone proteins and vascular endothelial growth factor. Invading blood vessels erode the hypertrophic cartliage and bring osteoblasts to replace cartilage with bone. FGF-18 prevents chondrocyte maturation.
Where does the centrum of the vertebra originate?
Derived from ventral and medial parts of paired sclerotomes
Differentiate hox gene boundaries for different regions of vertebral column.
Hox-3 is occipital cervical boundary
Hox-6 is cervical thoracic boundary
Hox-9 is attached-floating rib boundary
describe development of axis/atlas complex and id primordia.
In a mouse the atlas is developed from a combination of Hoxa1, Hoxa3, Hoxb1 and Hoxd4.
The axis is the same four genes plus Hoxa4 and Hoxb4
Where does the neural arches come form?
dorsal regions of sclerotomes
What is the relation between formation of neural arches and spina bifida?
The neural arches form a protective roof over the spinal cord when they fuse together. If they do not fuse all the way it reults in spina bifida.
Where do the costal cartilages and ribs originate from?
Proximal development depends on expression of myotomic myogenic factors myf-5 and myf-6. Distal development depends on BMP signals from somatopleural mesoderm
What is the relationship of Hox gene expression and development of the vertebral column.
Hox genes differentiate regional boundaries of the vertebral column.
How does RA affect expression of hox genes and development of the vertebral column?
RA causes a cranial shift in which the last cervical vertebra is transformed into the first thoracic vertebra. If given later it causes a caudal shift in which thoracic vertebra extend into lumbar vertebrae.
What are homeotic transformations?
Transformations of hox genes that results in shifts in cranial or caudal levels in overall segmentation and organization of vertebrae.
Relate anterior expression boundaries of key hox gene paralogues and major boundaries in axial skeleton.
Posterior extension of axial skeleton is balanced by Cdx and homeobox genes which promote extension. Also the Hox13 paralogue which slows and stops the extension.
Single Hox gene knockouts?
Likely to produce a minor defect but not same extent as knockout of all paralogues.
Knockout of all Hox 10 paralogues?
Ribs form on all the lumbar and sacral vertebrae. Hox10 represses the influence of more anterior genes
Knockout of all Hox 11 paralogues?
Suppresses influence of Hox10 and allows sacrum to form
Mutation of single hox gene?
Minor anatomical defect
Describe the origin of the sternum.
Derived from lateral plate mesoderm arises as a pair of cartilaginous bands. Fused cartilaginous bands secondarily subdivide into craniocaudal elements
Describe origin of clavicle.
Arises from neural crest and follows intramembtanous pathway. One of the first bones to become ossified.
What is cleiodcranial dysplasia?
Birth defect that affects bones and teeth. Clavicles poorly developed or absent and shoulders are brought close together
What are the subdivisons of the developing skull?
Neurocranium, Viscerocranium, occipital sclerotomes
Describe the generalized viscerocranium and bones that develop from viscerocranium.
Surrounds the oral cavity and pharynx. Comes from neural crest. Has cartilaginous portion and membranous. Cartilaginous forms the pharyngeal arch I and II. Membranous forms temporal,,zygomatic, maxillary, nasal, lacrimal, palatine, vomer, pterygoid plates
Describe the generalized viscerocranium and bones that develop from viscerocranium.
Surrounds the oral cavity and pharynx. Comes from neural crest. Has cartilaginous portion and membranous. Cartilaginous forms the pharyngeal arch I and II.
Describe origin of various endochondral skull bones.
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Describe origin of various endochondral skull bones.
CANT FIND
What four components do each pharyngeal arch consist of?
Skeletal element
muscles
branch of specific cranial nerve
artery
Elongation of primary ossification centers is due to what?
Shh
Elongation of primary ossification centers is due to what?
Shh
What bones develop from the membranous viscerocranium?
Membranous forms temporal,,zygomatic, maxillary, nasal, lacrimal, palatine, vomer, pterygoid plates
