critical thinking

1. Hematoma formation: Blood and fribrous tissue accumulates at the fracture site. White blood cells are also attracted and eventually clean up the fractured site.

2. Callus formation: Fibrous tissue is converted to cartilage, and then gradually into spongy bone.  Notice how this is similar to the strategy used for rapid growth in the fetus.  Use fibrous tissue or cartilage first to quickly establish the area you will convert to bone.  This is sometimes categorized as two separate steps - fibrocartliage callus formation, and bony callus formation - but both parts are occuring at the same time.

3. Remodeling: Callus formation is inexact, and produces spongy bone in places where compact bone is required. The weeks that follow will find osteoblasts and osteoclasts reshaping the bone back to its original dimensions and composition.

You wouldn't have healthy bones There are three types of bone cells, and each one has a purchase. There are osteoclasts that break down and remove old bone, osteoblasts that build new bone, and osteocytes that carry nutrients to the bone. You need all three!

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Hi again,

Cartilage has greater resilience because its matrix lacks bone salts, but its cells receive nutrients via diffusion from blood vessels that lie external to the cartilage. By contrast, bone has a beautifully engineered system of canaliculi for nutrient delivery, and for that reason its regeneration is much faster and more complete.

Predict why bone is not used every place a hard skeletal element is needed