Bones support, move, and protect the body; they also give us our features. But without bone cells we would have no bones. Bone cells are the living units that make up your bones and keep them functioning. Bone cells have two major roles, which are the production of new bones and resorption or destruction of old bone. They also carry out other small roles. There are four main types of bone cells: Osteogenic, which are bone cells that respond to traumas, osteoblasts, which form bone matrix around themselves by laying down collagen fibers and depositing the hard mineral material, osteocytes, which respond to the bodies need for lower or higher circulating level of minerals contained in the bone and osteoclasts, which break down bone tissue. Bone cell replacements have a turn over time of ten years in humans. The definition of turnover time is the renewal of the matrix and the bone cells. The matrix of bone cells is the “intercellular substance of bone, consisting of collagenous fibers, ground substance, and inorganic salts”(Bone Matrix, Par. 2). Inside the bone cells and all other cells are organelles. Organelles are tiny organs in the cell. The nucleus is a large, often spherical body and has many gates that are called nuclear pores. The nucleus serves, as the control center of the cell. Within the nucleus is the nucleolus, which has the distinct responsibility of manufacturing ribosomes. Ribosomes are small organelles made out of protein and RNA and they assemble amino acids into complex proteins. The mitochondrion is an organelle that produces energy for the cell. If many mitochondria are seen within the cell it usually indicates that it is very active. Lysosomes are spherical membranes that break down proteins and other cell parts for recycling. Vacuoles a spherical membrane holds food and other materials until needed. One of the most important organelle in the bone cell is the Golgi apparatus. The Golgi apparatus has four major functions. First they wrap or
