4.1.3 Musculoskeletal Development Flashcards
The myotome developes into the?
differentiates into myoblasts which comprise the segmented trunk musculature
The dermatome developes into?
contributes to the formation of the dermis of the skin
Describe the process of limb bud development?
Limb buds are derived from somatopleure,but the limb muscles and vasculature develop from somites.
Answer : A and E
How do the Hox genes apply to body axis development?
Regulated by retanoic acid
Hox genes are critical for establishing limb formation and specification. Hox genes determine where limbs will form along the length of the developing fetus. Genes with the same number, but positioned on different chromosomes, form a paralogous group.Expression of genes is in a cranial-to-caudal direction from the 3’ (expressed early) to the 5’ (expressed later) end as indicated in the fly and human embryo diagrams. Retinoic acid (RA) modulates expression of these genes, with those at the 3’ end being more responsive to the compound.
How do the Hox genes apply to limb development?
Proximal to distal axis
What is the role of the apical ectodermal ridge in controlling the proximal-distal axis?
There are 3 segments of the developing limb: stylopod (blue), zygopod (amber), and autopod (green). The apical ectodermal ridge contains members of the Fibroblast Growth Factor (FGF) family of growth factors that influence the cells in the progress zone which is labeled PZ on the next slide. The apical ectodermal ridge controls positional information and/or cell death in the mesenchymal cells of the progress zone (PZ).
What is the role of the zone of polarizing activity in cranial-caudal axis.
Retinoic acid and Sonic hedgehog (Shh) are morphogens—their concentration varies from high to low across the limb establishing the cranial-caudal (anteroposterior) axis. ZPA organizes anteroposterior axis and produces retinoic acid which induces Sonic hedgehog (Shh). Shh defines the ZPA. Differentiation of the digits is dependent on concentration of morphogen and duration of exposure.
D. Wnt 7
Apical ectodermal - proximal distal
Zone of polarizing -cranial caudal
RA - ZPA
Describe the rotation of the limbs?
Limbs initiall extend caudally
Later, limbs extend ventrally
Upper and lower limbs rotate in different directions and to different degrees
Upper limbs rotate laterally almost 90 - elbow will point back
Lower limbs rotate medially almost 90 - knee will point anterior
How are dermatomes initially organized?
What are the characteristics of limb malformations?
What is amelia? Meromelia? Phocomelia?
What are the characteristics of congenital clubfoot?
What separates the digits of hand and toes?
Apoptosis of the tissue in between the digits
The important concept on this slide is the mechanism for differentiation of individual digits from webbed-hands and feet (fingers and toes). Please remember that the apical ectodermal ridge (AER) has “moved” to the end of the extremity (hand or foot). Cell death in the AER creates separate ridges for each digit. Cell death in the interdigital spaces produces separation of the digits. Digit separation is complete at about 56 days of development (timing provided for information purposes only!). The apoptotic events are important conceptually and test-wise.
What is a congenital hip dislocation?
What is phocomelia?
Describe the innervation of the epaxial and hypaxial division?
How do the vertebrae form?
Intersegmental formation of the vertebrae. Also see the video entitled verterba.
What are the characteristics of achondroplasia?
What are the different types of Spina Bifida
Occulta Lumbar tuft of hair - defect of vertebral column
Describe the development of skin.
What is the Vernix Caseosa?
What are the mesoderm derivatives?
What determine the Dorsoventral patterning?
