In this i describe all type of bone cells and their functions

2. BONE
• Bone is a specialized connective tissue,
which makes up the body skeleton and is
one of the hardest structures of the
animal body.
• Bone or osseous tissue represents the
highest differentiation among supporting
tissues.

3. COMPOSITION OF BONE
ORGANIC PART
33%-35%
• COLLAGEN: 88-90% TYPE 1
• NON COLLAGEN:10-11%
A) GYLCOPROTEINS 6-9%(EX.OSTEONECTIN)
B) PROTEOGLYCANS 8%
C) SIALOPROTEINS 35%
D) LIPIDS 4%
INORGANIC PART
65%-67%
• CALCIUM
• PHOSPHATE
• MAGNESIUM
• TRACE ELEMENTS: Nickel, iron, Fluoride, cadmium,
zinc, magnesium

4. OSTEOPROGENITOR CELLS
• Derived from mesenchyme
stem cells in bone marrow.
• Undergo mitosis and develop
into "osteoblasts“
• Found on inner surface of
periosteum and endosteum.

5. OSTEOBLASTS
• They are mononucleated cells responsible for
the synthesis and secretion of the
macromolecular organic constituents of bone
matrix.
• Osteoblasts are cuboidal or slightly elongated
cells.
• The cells are found on the forming surface of
growing or remodeling bone.
• They form a protein mixture known as osteoid
(primarily type I collagen), which mineralizes to
become bone.

6. FUNCTIONS OF OSTEOBLAST
• Formation of new bone via synthesis of
various proteins and polysaccharides.
• Regulation of bone remodeling and mineral
metabolism.
• Osteoblasts also secrete small amount of type
I collagen, osteonectin, osteopontin, RANKL,
proteoglycans, proteases, growth factors etc.
• Osteoblasts recognize the resorptive signal
and transmit it to the osteoclast.

7. OSTEOCYTES
• The number of osteoblasts that
becomes osteocytes depends on the
rapidity of bone formation.
• Within the bone matrix, the
osteocyte reduces in size, creating a
space around it called the osteocytic
lacuna.
• Normally the most abundant cells in
bone, the almond shaped osteocytes
exhibit significantly less RER, smaller
Golgi complexes, and more
condensed nuclear chromatin than
osteoblasts

8. FUNCTIONS OF OSTEOCYTES
• Maintains the integrity of the lacunae
and canaliculi.
• Keep open the channels for diffusion of
nutrients through bone.
• Play role in removal and deposition of
matrix and of calcium when required.
• They release proteins that
inhibit/stimulate/other bone cells-
osteoblasts and osteoclasts.

9. OSTEOCLASTS
• The large size and multinucleated
condition are due to their origin from the
fusion of bone marrow–derived
monocytes.
• osteoclasts on the bone surface lie within
enzymatically etched depressions or
cavities in the matrix known as resorption
lacunae (or Howship lacunae).
• In an active osteoclast the membrane
domain that contacts the bone forms a
circular sealing zone which binds the cell
tightly to the bone matrix and surrounds
an area with many surface projections,
called the ruffled border.

10. Function of Osteoclasts
• Osteoclasts are the cells that degrade
bone to initiate normal bone
remodeling and mediate bone loss in
pathologic conditions by increasing
their resorptive activity.
• Osteoclast pumps protons to acidify
and promote dissolution of the
adjacent hydroxyapatite, and releases
matrix metalloproteinases and other
hydrolytic enzymes from lysosome-
related secretory vesicles for the
localized digestion of matrix proteins.

11. REGULATION OF OSTEOCLAST ACTIVITY