Cartilage is derived from mesochyme and forms a matrix for bones, ends of bones, intercostals from ribs, nose, ears etc. Name the three major types of cartilage. Bone can either be dermal or replacement. Dermal bone forms directly in the skin from mesenchyme. Osteoblasts form a calcium phosphate matrix and deposit salts, they then become osteocytes.
Dermal bones are plate like, but can become thicker or grow at the edges.
Membrane bones are deep bones that also do not have a primary cartilage matrix. Give some examples of dermal bones seen in this lab. New cartilage grows mainly at the ends and at epiphyses to lengthen the bone. To widen it, the periosteal membrane directly secretes perichondrial bone in strips. The axial skeleton was derived from scleratome, the appendicular skeleton from myotome.