1. Bones

2. The bones and cartilages of the human skeleton
Epiglottis
Larynx
Cartilage in
external ear
Cartilages
in nose
Trachea
Lung
Cartilage in
intervertebral
disc
Articular
cartilage
of a joint
Costal
cartilage
Respiratory
tube cartilages
in neck and thorax
Pubic
symphysis
Meniscus
(padlike cartilage
in knee joint)
Key:
= Bones of axial skeleton
= Bones of appendicular skeleton
Articular
cartilage
of a joint
= Hyaline cartilages
= Elastic cartilages
= Fibrocartilages

3. Hyaline cartilage
H [amp ] E ×150 (b) Thin epoxy resin section, toluidine blue ×1200;
Cb chondroblasts Cc chondrocytes L lipid droplet M cartilage matrix N nucleus P perichondrium

4. Fibrocartilage H [amp ] E/Alcian blue ×320

5. Elastic cartilage Elastic van Gieson ×128

6. Cortical (compact) bone Ground sections, unstained
TS ×80 (b) TS ×600 (c) LS ×150; C bone canaliculi
H1 and H2 Haversian systems HC Haversian canals I interstitial system
L lacunae V Volkmann's canal

7. Classification of bones on the basis of shape
Flat bone (sternum)
(a)
Long bone (humerus)
(d)
Irregular bone (vertebra),
left lateral view
(b)
Short bone (triquetral)

8. The structure of a long bone (humerus of arm)
Spongy
bone
Spongy bone
Compact bone
Proximal
epiphysis
Articular
cartilage
Articular
cartilage
Epiphyseal
line
Periosteum
Endosteum
Compact bone
Medullary
cavity
(b)
Yellow
bone marrow
Diaphysis
Compact bone
Periosteum
Perforating
(Sharpey’s)
fibers
Nutrient
arteries
Distal
epiphysis
(a)
(c)

9. Artery with capillaries Structures in the Vein central canal
A single osteon
Artery with
capillaries
Structures
in the
central
canal
Vein
Nerve fiber
Lamellae
Collagen
fibers
Twisting
force

10. Microscopic anatomy of compact bone
Lamella
Osteocyte
Osteon
(Haversian system)
Circumferential
lamellae
Lamellae
Lacuna
(b)
Canaliculus
Central (Haversian) canal
Blood vessel continues
into medullary cavity
containing marrow
Osteon
Spongy bone
Perforating
(Sharpe’s)
fibers
Compact
bone
Periosteal
blood vessel
Lacuna
Central (Haversian) canal
Periosteum
Perforating (Volkmann’s) canal
Blood vessel
(c)
(a)
Endosteum lining bony canals
and covering trabeculae
Central
canal
Interstitial
lamellae

11. Periosteum (a) Inactive: H [amp ] E ×128 (b) Active: H [amp ] E ×200

12. Ossification
Intramembranous: patelas
Endochondral: epiphysis

13. Intramembranous ossification
Mesenchymal cell
Collagen fiber
Ossification center
Osteoid
Osteoblast 1
An ossification center appears in the fibrous connective
tissue membrane.
•Selected centrally located mesenchymal cells cluster and
differentiate into osteoblasts, forming an ossification center.
Osteoblast
Osteoid
Osteocyte
Newly calcified
bone matrix 2
Bone matrix (osteoid) is secreted within the fibrous
membrane.
• Osteoblasts begin to secrete osteoid, which is mineralized
within a few days.
• Trapped osteoblasts become osteocytes.

14. Intramembranous ossification (continued)
Mesenchyme
Condensing
to form the
periosteum
Trabecula of
woven bone
Blood vessel 3
Woven bone and periosteum form.
• Accumulating osteoid is laid down between embryonic blood
vessels, which form a random network. The result is a network
(instead of lamellae) of trabeculae.
• Vascularized mesenchyme condenses on the external face of
the woven bone and becomes the periosteum.
Fibrous
periosteum
Osteoblast
Plate of
compact bone
Diploë (spongy bone)
cavities contain red
marrow 4
Bone collar of compact bone forms and
red marrow appears.
• Trabeculae just deep to the periosteum thicken, forming a
woven bone collar that is later replaced with mature lamellar
bone.
• Spongy bone (diploë), consisting of distinct trabeculae, persists
internally and its vascular tissue becomes red marrow.

15. Intramembranous ossification H [amp ] E ×75;
B woven bone M primitive mesenchyme Ob osteoblas

16. Endochondral ossification in a long bone
Secondary
ossificaton
center
Articular
cartilage
Spongy
bone
Epiphyseal
blood vessel
Deteriorating
cartilage
matrix
Hyaline
cartilage
Epiphyseal
plate
cartilage
Spongy
bone
formation
Primary
ossification
center
Medullary
cavity
Bone collar
Blood
vessel of
periosteal
bud 1
Formation of
bone collar
around hyaline
cartilage model. 2
Cavitation of
the hyaline carti-
lage within the
cartilage model. 3
Invasion of
internal cavities
by the periosteal
bud and spongy
bone formation. 4
Formation of the
medullary cavity as
ossification continues;
appearance of sec-
ondary ossification
centers in the epiphy-
ses in preparation
for stage 5. 5
Ossification of the
epiphyses; when
completed, hyaline
cartilage remains only
in the epiphyseal plates
and articular cartilages.

17. Growth in length of a long bone
Resting
(quiescent) zone
Growth
(proliferation)
zone
Cartilage cells
undergo mitosis
Hypertrophic
zone
Older cartilage
cells enlarge
Calcified
cartilage
spicule
Calcification
zone
Matrix becomes
calcified; cartilage
cells die; matrix
begins deteriorating
Osteoblast
depositing
bone matrix
Ossification
(osteogenic)
zone
New bone
formation
is occurring
Osseous
tissue
(bone)
covering
cartilage
spicules

18. Long bone growth and remodeling during youth
Articular
cartilage
Growth
Remodeling
Bone grows in
length because:
Growing shaft
is remodeled by: 1
Cartilage
grows here 1 2
Bone
resorbed
here
Cartilage
replaced by
bone here
Epiphyseal
plate 3 2
Cartilage
grows here
Bone
added by
appositional
growth here 4
Cartilage
replaced by
bone here 3
Bone
resorbed
here

20. Epiphysial growth plate H [amp ] E/Alcian blue ×40

21. Endochondral ossification - metaphysis H [amp ] E/Alcian blue ×198

22. Stages in the healing of a bone fracture
External
callus
Hematoma
Bony
callus of
spongy
bone
Internal
callus
(fibrous
tissue and
cartilage)
New
blood
vessels
Healed
fracture
Spongy
bone
trabeculae 1
Hematoma
formation 2
Fibrocartilaginous
callus formation 3
Bony callus
formation 4
Bone remodeling

23. Bone remodelling and repair H [amp ] E ×480; B bone D cartilage degeneration
E epiphyseal cartilage GP epiphysial growth plate H hypertrophy zone M maturation zone
O osteogenic zone Ob osteoblast Oc osteoclast P proliferative zone R reserve cartilage zone
SC secondary ossification centre V blood vessels WB woven bone

24. Bone anatomy and stress
Load here
(body weight)
Head of
femur
Compression
here
Tension
here
Point of
no stress