Bone Structure
Bone Structure in General

Bone is a type of connective tissue

It is as strong as steel but as light as aluminum

It is a moist living tissue that constantly breaks down
and rebuilds itself

Each bone adjusts its shape and size during the
growing process, after injury, and in response to
stress

A bone’s shape makes possible its functions

Bony projections called processes provides sites of
attachment for ligaments and tendons

Grooves and openings are passageways for blood
vessels and nerves
Parts of a Long Bone
 Long
bones are
divided into three
regions
Epiphysis
Metaphysis
Diaphysis
Epiphysis

Is the expanded portion at the end of each
long bone

It forms a joint (articulates) with another bone

The proximal epiphysis is the end nearest the
torso

The distal epiphysis is the end farthest from
the torso

The outer surface of the epiphysis is covered
with a layer of hyaline cartilage called articular
cartilage
Diaphysis & Metaphysis

The diaphysis is the
shaft of the long
bone

The metaphysis is the
widening part of the
bone between the
epiphysis and
diaphysis
Internal Long Bone Structure
Long bone consists of a porous central cavity
surrounded by a ring of dense material
 The layers from the outside to the inside of
bone are:
 Periosteum
 Compact bone
 Spongy bone
 Medullary cavity
 Endosteum
 Marrow

Periosteum



Is a tough membrane
that covers the surface
of the bone
It doesn’t cover the
articular cartilage on its
ends
It contains a network of
blood vessels and nerves,
which supply nutrients and
signal pain
Compact Bone
Is a hard thick layered
material that enables
bone to endure large
amounts of stress
 It makes up the wall of
the diaphysis
 It is also known as
cortical bone
 Its extracellular matrix
is continuous with no
gaps

Spongy Bone
Composes mainly the epiphysis
of bone
 It is also known as cancellous
bone
 It consists of many branching
bony plates called trabeculae
 Irregular connecting spaces
between the trabeculae help
reduce the bone’s weight
 The bony plates are most highly
developed in the regions of the
epiphyses subjected to
compressive forces

Medullary Cavity, Endosteum, &
Marrow

In the diaphysis, compact bone forms a
semi-rigid tube with a hallow chamber called
the medullary cavity

This cavity is continuous with the spaces of
spongy bone

A thin membrane containing bone-forming
cells, called the endosteum lines it

A specialized connective tissue known as
marrow, fills it

Marrow comes in two forms red & yellow
Internal Long Bone
Structure
Microscopic Structure of Compact Bone
Compact bone is composed of cylinders of
mineral crystals and protein fibers called
lamellae
 In the center of each lamellae is a narrow
channel called a Haversian canal
 Blood vessels run through interconnected
Haversian canals, supplying nourishment to the
bone tissue
 Wrapped around each Haversian canal are
layers of protein fibers
 Haversian canals are connected to each other
via Volkmann’s canals, which carry a blood
vessel, nerve, and lymph vessel

Microscopic Structure of
Compact Bone

Embedded within the large gaps between the
protein layers are bone cells, known as osteocytes

Each osteocyte is embedded in fluid filled cavities
called, lacunae and surrounded by concentric
layers of bone matrix, lamellae

The lamellae and lacunae together form an osteon

The lacunae are connected to one another and to
Haversian canals by a system of interconnecting
canals called canaliculi
Internal Bone Structure