Osteogenic cells stem cells found in endosteum and

- Osteogenic cells : stem cells found in endosteum and inner layer of periosteum.
+ arise from embryonic mesenchymal cells.
+ multiply continuously and five rise to most other bone cell types.
- Osteoblasts : bone-forming cells.
+ form single layer of cells under endosteum and periosteum
+ Nonmiotic
+ Synthesize soft organic matter of matrix which then hardens by mineral
deposition.
+ Stress stimulates osteogenic cells to multiply rapidly and increase the
number of osteoblasts which reinforce bone.
+ Secrete hormone osteocalcin (stimulates insulin secretion of pancreas;
increases insulin sensitivity in adipocytes which limits the growth of
adipose tissue).
- Osteocytes : former osteoblasts that have become trapped in the matrix they deposited
+ Lacunae: tiny cavities where osteocytes reside
+ Canaliculi: little channels that connect lacunae
+ Cytoplasmic processes of osteocytes reach into canaliculi and contact
processes of neighboring cells (gap junctions allow for passage of nutrients wastes,
signals).
+ Some osteocytes reabsorb bone matrix while others deposit it.
+ Act as strain sensors- when stressed, produce biochemical signals that
regulate bone remodeling (shape and density changes that are adaptive).
- Osteoclasts : bone dissolving cells found on bone surface.
+ osteoclasts develop from same bone marrow stem cells that give rise to
blood cells (different origin from other bone cells)
+ Ruffled border (large surface area) faces bone.
+ Cells often reside in resorption bays (pits in bone surface).
+ Dissolving bone is part of bone remodeling.
4. Bone matrix is 2/3 (inorganic/organic) and 1/3 (inorganic/organic)?
5. Differentiate between Rickets and Osteogenesis imperfecta (Brittle Bone Disease).
- Rickets is a disease caused by mineral deficiency and resulting in soft, deformed bones.
- Osteogenesis imperfecta (brittle bone disease) results from a defect in collagen
deposition.
6. Differentiate between interstitial, concentric, and circumferential lamellae.

- Interstitial lamellae: fill irregular regions between osteons,
- Concentric lamellae: surround a central (Haversian) canal running longitudinally.
- Circumferential lamellae: fill outer region of dense bone.
7. Differentiate between red and yellow bone marrow function.
- Red marrow (myeloid tissue): contains hemopoietin tissue: produces blood cells.
+ In nearly every bone in a child
+ In adults, found in skull, vertebrae, ribs, sternum, part of
pelvic girdle, and proximal heads of humerus and femur.
- Yellow marrow found in adults
+ Fatty marrow that does not produce blood.
+ Can transform back to red marrow in the event of chronic
anemia.