2. Bone Remodeling

Just like my 100 yr old house that's constantly undergoing remodeling--tearing down and then building up--bones constantly undergo a dynamic remodeling.  Osteoclasts are bone cells that tear down bone structure and osteoblasts build them up.  Bones are healthiest when osteoclasts and osteoblasts balance.

When osteoclasts outrun osteoblasts--tearing down without repair--bones become less dense and more vulnerable to fracture.  It's okay to remove some studs in that wall that you've decided to take down, but if you don't replace that support with horizontal beams or replacement vertical studs, then the house is weakened, vulnerable to winds, earthquakes, whatever, a house of twigs .