The musculoskeletal system of vertebrates has two subsystems. The Axial system comprises the vertebrae and ribs, and their associated musculature. The Appendicular system includes the pelvic and pectoral girdle, the paired fins or limbs.
Axial System (yellow)
Appendicular System (red)
Two populations of embryonic mesoderm provide the cells for the muscle, bone and connective tissue for both axial and appendicular structures. The somitic mesoderm supplies cells for the axial skeleton, while the lateral plate mesoderm supplies the cells for the connective tissue and skeleton of the appendicular system. All the striated muscles of both systems arise from the somites.
A long history of experimental embryology has demonstrated that in most embryonic systems of higher vertebrates, cell fate is not autonomously determined, but is context dependant. This means that neighbors are all important, and can produce what is known as the "community effect", in which cells capable of a wide range of fates when isolated, will conform to the activity of their neighbors when part of the "community". This means that cells can regulate their behavior in response to environmental clues. From a developmental perspective, such behavior can be seen to play an important role in morphological evolution by providing flexibility and buffering from both environmental and genetic variability.
In the Burke lab, we explore the nature of the "information" that determines the patterning of mesodermal cells as they form musculoskeletal elements. For instance, we ask whether cells in the somites already "know" what they should become before they advance out of the early somitic epithelium, or whether they depend on their surroundings to ‘tell’ them what to do.
These animations depict the basic behavior of embryonic cells in the somitic and lateral plate mesoderm that generates the final arrangement of muscle and bone in the avian neck and trunk. These animations are based on observations of normal development, and therefore present descriptive empirical data. Data describing developmental patterns is collected and analyzed in order to build hypotheses about the underlying mechanisms responsible for the phenomenology. Once the pattern of normal morphogenesis is understood, experimental methods can be used to investigate the relationships between different cell populations, and the causation of developmental events, such as migration and differentiation.
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