A&P Chapter 9.6, Bone Resorption by Osteoclasts
Bone resorption
When the minerals in bone are absorbed back into the blood a second time The destruction of bone matrix and subsequent minerals into the blood
Function of enzymes of bone resorption
(step 2) Breaks down collagen fibers distributed throughout ground substance of bone matrix
Function of acids in bone resorption
(step 2) Dissolves mineral salts in ground substance of the matrix
Function of ruffled membranes of osteoclasts in bone resorption
(step 2) Engulfs pieces of digested bone matrix by phagocytosis
The stages of bone resorption (3)
Development of osteclasts Secretion of acids and enzymes Formation of resorption pit
Resorption Pit
Also called Howship's lacuna The resulting dimple on bone surface due to the work of osteoclast
Ruffled membrane
Characteristic of osteoclast Plasma membrane of these cells that come in contact with the bone surface has hundreds of tiny, finger-like processes Increases osteoclast's surface area, which helps it destroy bone matrix
Osteoclast
Most important cell in bone resorption (most important bone matrix destroying cell) Multinucleated Found mostly in endosteum (some are found in periosteum, but now many) The product of many monocytes fusing together Contains a ruffled membrane
What happens with calcium at the end of the last stage of bone resorption
Much of the calcium enters the blood stream, Therefore, as osteoclasts become more active, the amount of calcium ions in the blood rises
What two cells aid in bone resorption
Ostecytes (minor) Osteclasts (major)
Development of osteoclasts
Stage one of bone resorption Monocytes fuse together to from a single osteoclasts
Secretion of acids and enzymes
Step 2 of bone resorption Where true bone resorption begins Osteoclasts secrete acids and enzymes onto the bone surface, and the cells' ruffled membrane help too
Formation of Resorption Pit
Step 3 of bone resorption The creation of a resorption pit (Howship's lacuna) as osteoclasts does its work
Why its called bone resportion
The materials originally went from the blood to the bone (digestion gathered the nutrients and gave it to bone), and now its going from the bone back to the blood