Osteoblasts,osteoclasts+and+osteocytes

[|Bone Cells overhead2.doc] Haversian System or Osteon

Video : http://www.youtube.com/watch?v=rHyeZhcoZcQ


 * __Haversian Canal-__** has arteries and veins that supply blood and nutrients to the bone
 * __Canaliculi-__** small canals that supply blood to the osteocytes
 * __E.C.M.-__** stores Calcium, Phosphorus, and collagen fibers; nothing can travel through it because it is very strong.
 * __Osteocytes-__** mature bone cells
 * __Lacuna-__** small cavity osteocytes are in
 * __Lamella-__** the concentric (circular) arrangement of extracellular matrix (E.C.M.). They provide strength.

Trabecula of lower jaw: .
 * __Osteoblast__-** A cell that makes bone. It does so by producing a matrix that becomes mineralized. Bone mass is maintained by a balance between the activity of osteoblasts that form bone and other cells called osteoclasts that break it down
 * __Osteoclast-__** A cell that nibbles at bone, breaks down bone, and is responsible for bone resportion.
 * Osteoclasts are large multinucleated cells (cells with more than one nucleus) that differentiate from another type of cell called a macrophage.
 * In normal bone, bone formation and bone resorption are closely coupled processes involved in the normal remodeling of bone.
 * In osteoporosis, the net rate of bone resorption exceeds the rate of bone formation, resulting in a decrease in bone mass without a defect in bone mineralization.
 * In women, osteoclast activity is increased because of decreased estrogen after the menopause . (Men with prematurely decreased testosterone may also have increased osteoclast activity.) These changes result in further net loss of bone. The amount of bone available for mechanical support of the skeleton eventually falls below the fracture threshold and one may suffer a fracture with little or no trauma.
 * __Osteocytes-__** The most abundant cell found in compact bone. Osteocytes are networked to each other by long cytoplasmic extensions that occupy tiny canals called canaliculi, which are used for exchange of nutrients and waste

[|Haversian System Video] [|Haversian System Video 2]