Describe the role of the following cells and structures: mesenchymal cells, osteogenic cells, osteoblasts, lacunae, osteocytes, and osteoclasts.

Mesenchymal Cells : Mesenchyme in vertebrate is a type of connective tissues found mostly during embryo development. It comprises of ground substance with few cells or fibres. Its is also referred to a group of mucoproteins which are found in different types of cysts resembling like that of mucus. Mesenchymal cells are productive stromal cells that can be divided into different varieties of cells like osteoblasts, chondrocytes, myocytes and adipocytes. These are the adult stem cells which are found in the bone marrow. However these cells can be extracted from other tissues including peripheral blood, fetal liver, lung fallopian tube and cord blood. These are found in bone marrow significant for renovation of skeletal tissues such as cartilage, bone & fat found in bone marrow.

Osteogenic Cells : They are the only bone cells which differentiate. They differentiate & forms into osteoblasts which are responsible for new bones formation. They are located deeper into the periosteum and bone marrow.

Osteoblasts : Osteoblasts work in sets known as osteons to make the osteoid matrix and they release it at regulated times to develop the new bone tissue where it is mostly required. Osteoblasts formation & activity enlarges in contrast to growth factors & physical activities so that stronger bones can be formed. They are found in large numbers in periosteum and in endosteum. Normally all of the bone matrix in air breathing vertebrates is mineralized by osteoblasts.

Lacunae : Lacunae are the small spaces between the lamellae where osteocytes are located. They are linked together by minute networks called canaliculi. These networks provide a pathway through which a nutritives reach osteocytes and so the waste products leave them.

Osteocytes : Osteocytes are the cells which lies within the substance of fully developed bone. It occupies a small compartment called lacunae which is located in the calcified matrix of bone. They are mature osteoblasts which are surrounded by the products they secreted. Osteocytes continue to develop bone to some extent which is significant for the maintenance of the strength and health of bone matrix. However they still perform the functions which are beyond maintenance.

Osteoclasts : These are large cells with multiple nucleus which are evolved from another types of cells called macrophage. These are the large cells which dissolve the bone. They are derived from bone marrow and are related to white blood cells. They are found on the bone mineral's surface next to the dissolving bone.