Assertion: bone's layer | /r/CapableOf | narrow the channel
Facets:
value: slowly
type: MANNER
value: until a tunnel
type: OTHER
Source sentences:
text: Layers of bone-forming cells, or osteoblasts, follow the osteoclasts and lay down new bone on the sides of the channel; the layers of bone built up in this way slowly narrow the channel until a tunnel not much larger than the central blood vessel remains.