Question

1) The Shh (sonic hedgehog) signaling molecule is important for patterning the dorsal-ventral axis of the spinal cord. Briefly describe where Shh is expressed and how its expression patterns the spinal cord.

2)What is the role of the proliferating chondrocytes and hypertophic chondrocytes in bone development and bone growth?

a) Proliferating chondrocytes:

b) Hypertrophic chondrocytes:

Answer 1

1) Sonic hedgehog is a glycoprotein molecule, that is expressed throughout the central nervous system . It is very important during neurodevelopment, particularly through its induction of endogenous neural precursor cells and neural stem cells. The signaling system by which Shh, has its diffuse effects on multiple end organs depends on a downstream signaling cascade initiated by binding to the receptor Patched on Shh-specific target cells.

SSH, plays a critical role in organizing cell pattern in the developing spinal cord. In the spinal cord, distinct neuronal subtypes emerge in a precise spatial order from progenitor cells arrayed along the dorsal-ventral axis of the neural tube, and this pattern of neurogenesis is controlled by secreted signals that partition neural progenitor cells into spatially discrete domains

2) Proliferating chondrocytes: They produce and maintain the Cartledge matrix. This may lead you to ask why cartilage is important in the first place. One of the principal functions of some cartilage types is to keep bones from rubbing together. Such thing is called Reducing Friction.

Hypertrophic chondrocytes : are large and elongated in the direction of growth, with their proximal to distal length greater than half of the width. As the chondrocytes mature, they expand in area, especially in the hypertrophic zone.

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