Download Bone histology

Bone histology
Muhammed Asif BMLT, M.Sc (medical anatomy)
Dept. Of Anatomy
YMC.
DEFINITION
Bone is a dynamic, highly vascular specialized
connective tissue, which supports the body and
provides leverage for movements.
COMPOSITION OF BONE
Matrix
Cells
Organic
Inorganic
Osteoprogenitor cells
Osteoblasts
Osteocytes
Osteoclasts
Lamella
Lamella
Organic material
Inorganic material
Matrix
Calcium & phosphate
• Ground substance
Hydroxy – apatite crystals
• Collagen
MACROSCOPIC STRUCTURE
Shaft
– Periosteum
– Cortex
– Medullary cavity:
• Red or yellow bone marrow.
2 Ends:
– Covered by hyaline cartilage
Compact & spongy bone
Spongy bones
Structure of a Flat Bone
• Compact bone forms the outer shell of all bone and also the
shafts in long bones.
• Spongy bone is found at the expanded parts of long bones and
fills most irregular bones.
• Spongy or cancellous bone consists of a lattice of thin threads
of bone called trabeculae, which are lamellae that are arranged
as rods or plates and is less dense than compact bone.
Red bone marrow is found between the trabuculae.
Bone is covered by………????
Periosteum
The external surface of the bone is covered by a
connective tissue membrane called periosteum
except articular surface.
The periosteum consist of outer fibrous layer &
inner cellular layer.
The periosteum is united to underlying bone by
Sharpey’s fibers, but it is stronger where there is
attachment of tendons & ligaments.
Abundant periosteal arteries nourish outer part of
the cortex.
It is rich in nerve supply, which makes it more
sensitive.
MACROSCOPIC STRUCTURE
Shaft
– Periosteum
• Outer fibrous
• Inner cellular
– Cortex
• Compact bone
– Medullary cavity:
• Red or yellow bone marrow.
2 Ends:
– Covered by hyaline cartilage
Cortex
Lamella
Organic material
Inorganic material
Matrix
Calcium & phosphate
• Ground substance
Hydroxy – apatite crystals
• Collagen
• Ground substance consist of 25% water and glycosaminoglycans
(are of 3 different types i.e, hyaluronic acid, chondrotin sulphate &
keratan sulphate) and special glycoproteins (osteonectin &
osteocalcin).
• 25% Fibers – type 1 collagen fibers synthesized by osteoblasts.
• This fiber provide tensile strength & flexibility.
• 50% Inorganic material - Calcium & phosphate Provides
hardness, resistance to bending and forms about 65% of bone
weight.
Haversian canal
• Contains –
– Small amount loose
connective tissue
– Capillaries nerves and
– Lymphatics
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COMPOSITION OF BONE
Matrix
Cells
Organic
Inorganic
Osteoprogenitor cells
Osteoblasts
Osteocytes
Osteoclasts
Lamella
OSTEOPROGENITOR CELLS / OSTEOGENIC CELLS
• Stem cells of mesenchymal
origin.
• Present – endosteum,
periosteum & haversian canal
• Function - Proliferate and
convert themselves into
osteoblasts.
OSTEOBLASTS
• Oval in shape.
• Derived – osteogenic cells
• Found – wherever there is bone
formation
• Function
Synthesis and secretion of matrix.
Calcification of bone matrix.
OSTEOCYTES
• Derived from osteoblasts.
• Mature cell bone cells
• Star shaped
• Present in lacunae.
• Functions:
– Play a role in patency of
canaliculi for difussion of
nutrients
OSTEOCLASTS
• Large & multinucleated cell
• Cytoplasm – lysosomes &
mitochondria
• Present – sites of bone resorption
called pits of howships
• Function – helps in bone
resorption