1. Histology of bone
Dr. Marwa Gaffar Faki Ali
M.B.B.S, M.Sc. clinical anatomy

2. By the end of this session the student is
able to:
• Define bone tissue.
• Identify the different components of bone tissue.
• Identify the different types of bone tissue and their
histological features.
• Identify the osteon.

3. Introduction:
• Bone is a specialized type of connective tissue for
support.
• It is a mineralized tissue that gives mechanical and
metabolic functions to the skeleton.

4. Introduction:
Functions:
1. Support fleshy structures.
2. Protection of vital organs (brain, heart & lungs).
3. Harbors bone marrow (blood cells formation).
4. Reservoir of calcium.
5. Transform skeletal muscle contractions into body
movement.

5. Components of bone tissue:
Cells:
• Osteoblasts.
• Osteocytes.
• Osteoclasts.
Matrix:
• Intercellular calcified material.

6. Bone cells: Osteoblasts
• Bone forming cells.
• Found at surfaces of bone tissue.
• Synthesize the organic bone matrix.
• Active cells are cuboidal to colomnar in shape while flat ones
are inactive.
• Transformed into osteocytes.
Osteoblasts

7. Bone cells: Osteocytes
• Flat almond shaped.
• Situated in lacunae, one cell per lacuna.
• Communicate with each other through gap junctions.
• Actively maintain bone matrix.
• Osteocyte death is followed by matrix resorption.
Osteocye

8. Bone cells: Osteoclasts
• Large branched multinucleated motile cells.
• For resorption and remodeling of bone tissue.
• Found in Howships lacunae.
• Active osteoclasts have ruffled border facing bone matrix.
• Control is by cytokines and hormones (calcitonin).
Osteoclast

9. Bone cells

10. Bone matrix:
Inorganic matter:
• Calcium and phosphorus mainly.
Organic matters:
• Type I collagen.
• Ground substance.

11. Periosteum and endosteum:
• External and internal
coverings of bone.
• Composed of bone forming
cells and connective tissue.
• Function:
- Nutrition of osseus tissue.
- Provision of continuous
supply of osteoblasts
(repair &growth).

12. Periosteum & endosteum:
Periosteum:
• Outer layer of collagen fibers and fibroblasts.
• Inner layer of fibroblast like osteo-proginator cells.
• periosteal collagen fibers (perforating or Sharpeyfibers)
penetrate the bone matrix, binding the periosteum to
bone.
Endosteum:
• Lines all internal bone cavities by a single layer of flat
osteo-proginator cells.

13. Types & Organization of Bone:

14. Type of Bone Histological Features Major Locations Synonyms
Woven bone, newly
calcified
Irregular and random
arrangement
of cells and collagen;
lightly
calcified
Developing and
growing bones;
hard callus of bone
fractures
Immature bone;
primary bone;
bundle
bone
Lamellar bone,
remodeled from
woven bone
Parallel bundles of
collagen in thin
layers (lamellae), with
regularly
spaced cells between;
heavily
Calcified
All normal regions of
adult bone
Mature bone;
secondary bone
Compact bone,
~80%
of all lamellar bone
Parallel lamellae or
densely
packed osteons, with
interstitial
lamellae
Thick, outer region
(beneath
periosteum) of bones
Cortical bone
Cancellous bone,
~20% of all lamellar
bone
Interconnected thin
spicules or
trabeculae covered by
endosteum
Inner region of
bones, adjacent
to marrow cavities
Spongy bone;
trabecular bone;
medullary bone

15. Osteon or haversian system:
• Organization related to lamellar bone.
• Consists of lamellae organized concentrically around small
central canals containing blood vessels and nerves.

16. Osteon or haversian system:
• Within each osteon osteocytic lacunae occur between
the lamellae, with canaliculi radiating through the
lamellae, which allow all cells to communicate with the
central canal.