THE ARRANGEMENT OF LAMELLAR BONE IN THE DIAPHYSES – 3
The wall of the diaphysis is formed by thousands of very thin bone plates called bone lamellae (singular: lamella) made up of osteocytes surrounded by extracellular matrix. This wall is composed by three layers of lamellae.
1 – The external or outer circumferential lamellae made of stacks of slightly curved parallel lamellae placed at the periphery of the diaphysis. (Highlighted in blue).
2 – The inner border of the diaphysis, facing the bone marrow, is the internal or inner circumferential lamellae, formed by curved parallel lamellae.(Highlighted in red).
3 – The widest layer contain the intermediate lamellae, placed between both circumferential lamellae. This layer is occupied by Haversian systems and the spaces left between Haversian systems are filled with stretches of parallel bone lamellae. (Highlighted in green).
Excepting the articular surfaces, all internal and external surfaces of bones are covered by cell layers called respectively the endosteum and the periosteum. They cover the layer of bone lining cells (osteoprogenitors, active and inactive osteoblasts).
The endosteum is in direct contact with the medullary cavity and is usually formed by a thin layer of only one cell, similar to a simple, non stratified epithelium, whereas the periosteum is a thicker layer of connective tissue.
1 – The external or outer circumferential lamellae made of stacks of slightly curved parallel lamellae placed at the periphery of the diaphysis. (Highlighted in blue).
2 – The inner border of the diaphysis, facing the bone marrow, is the internal or inner circumferential lamellae, formed by curved parallel lamellae.(Highlighted in red).
3 – The widest layer contain the intermediate lamellae, placed between both circumferential lamellae. This layer is occupied by Haversian systems and the spaces left between Haversian systems are filled with stretches of parallel bone lamellae. (Highlighted in green).
Excepting the articular surfaces, all internal and external surfaces of bones are covered by cell layers called respectively the endosteum and the periosteum. They cover the layer of bone lining cells (osteoprogenitors, active and inactive osteoblasts).
The endosteum is in direct contact with the medullary cavity and is usually formed by a thin layer of only one cell, similar to a simple, non stratified epithelium, whereas the periosteum is a thicker layer of connective tissue.
