1. Osteoclast
(osteoclasts on bone surface)

2. KEY FUNCTIONS Partly Responsible for resorption
release the minerals, resulting in a transfer of calcium from bone fluid to the blood
Break down the bone matrix & attach themselves to the bone. They then create an acidic environment (due to the enzyme) underneath that dissolves the bone’s minerals
Multinucleate, High density of golgi bodies, mitochondria. And lysosomal vesicles

3. DIAGRAM
C) Due to there ruffled border, they Bind themselves to the bone with integrin and vitronectin. It now creates a polar micro- environnmet (Howship’s lacuna) where all the magic happens!
d)Ruffled border contacts the bone, secretes acid( tartrate-resistant acid phosphates (TRAP) and Cathepsin K ) that lowers the PH level
(d) Diagram showing the degradation of the inorganic matrix via the carbonic anhydrase II enzyme (CA II), disintegration of the organic matrix via cysteine proteinase (CP), collagenase (CL) and matrix metalloproteinase (MMP) enzymes and the transcytosis of the degraded products
 bone matrix into Ca2+, H3PO4, H2CO3, water and other substances
Derive from stem cells in the bone, monocytes (the same cell lineage that produces white blood cells)
b) depicting the role of RANK (receptor activator of nuclear factor kappa B), RANK ligand and osteoprotegerin
Regulated by RANK and the Rank Ligand of osteoblasts, triggers the formation of osteoclasts. OPG acts like a decoy and DECREASES osteaclastic activity

4. disorders
Not enough regulation of osteoclastic activation will degrade the bone
As you grow older remodelling cells get slower
osteopenia, Paget’s Disease and some types of bone cancer are affected by osteoclast malfunction.
pycnodysostosis, a hereditary osteopetrotic  disease, characterized by lack of functional cathepsin K expression

5. MULTIPLE CHOICE! How did you do?
 The sealing zone is the attachment of the osteoclast's ruffled border to the underlying ________.
Human skull b)human skeleton c) neck anatomy d)bone
Osteoclasts are characterized by their high content of secretion of ________ (TRAP) and cathepsin K.
Butyrylcholinesterase B) artrate-resistant acid phosphatas C) Calcineurin D) Arylsulfatase A
Osteoclasts formation requires the presence of ________ ligand 
TNFRSF1A b) PGO c) RANK D) integrin
At a site of active bone resorption, the osteoclast forms a specialized ________, the "ruffled border," that touches the surface of the bone tissue.
Cell membrane b) vesicle c) new cell d) polar nucleous
Which of the following is false about osteoclasts:
They are key in bone remodeling
They are automatically activated, with little regulation
through them, mineral ions are re-relaeased into the bloodstream
They break down the bone matrix during resorption
Multinucleated due to the merging of pre-cursor cells
ANSWERS!
D-BONE 2) B- TAR-TRATE RESISTANT ACID PHOSPHATES 3) C-RANK 4) A-CELL MEMBRANE 5)B- THEY ARE AUTOMIATICALLY ACTIVATED
How did you do?

6. REFERENCES http://www.youtube.com/watch?v=oQSXeR8i4A8
Science book