The skeletal system in the human body provides protection to the soft tissues, helps in the process of mineral homeostasis, and also does a production of blood cells. The skeletal system comprises connective tissues including cartilage, bone, ligaments, and tendons.
The skeletal system stores fats, minerals, and generates blood cells in the bone marrow, present in the long bones. Another prime function of the skeletal system is to help with mobility.
So, the given blank can be filled with blood cells.