Development Of The Musculoskeletal System //free\\ 99%

Joints develop in a proximodistal sequence (shoulder before finger joints) and are fully cavitated by week 12.

| Gestational Age | Key Developmental Event | | :--- | :--- | | | Mesoderm forms; somites begin to appear. | | Weeks 4–5 | Limb buds appear; cartilage models of bones form. | | Weeks 6–7 | Primary ossification centers appear in long bones; skeletal muscle fibers begin to form. | | Week 12 | Most bones have ossified primary centers; joints formed. | | Birth | Secondary ossification centers appear in epiphyses (bone ends) later in childhood. | development of the musculoskeletal system

This occurs primarily in the flat bones of the skull and the clavicle. Mesenchymal cells (stem cells) differentiate directly into bone-producing cells (osteoblasts), skipping the cartilage stage. This allows for the rapid expansion of the skull to accommodate the growing brain. Endochondral Ossification Joints develop in a proximodistal sequence (shoulder before