1. Figure 6.1 The bones and cartilages of the human skeleton.
Epiglottis
Larynx
Thyroid
cartilage
Cartilage in
external ear
Cartilages in
nose
Trachea
Cricoid
cartilage
Lung
Articular
Cartilage
of a joint
Cartilage in
Intervertebral disc
Figure 6.1 The bones and cartilages of the human skeleton.
Costal
cartilage
Respiratory tube cartilages
in neck and thorax
Pubic
symphysis
Bones of skeleton
Axial skeleton
Meniscus (padlike
cartilage in
knee joint)
Appendicular skeleton
Cartilages
Hyaline cartilages
Elastic cartilages
Fibrocartilages

2. (c)
Flat bone
(sternum)
(a)
Long bone
(humerus)
(b)
Irregular bone
(vertebra), right
lateral view
(d)
Short bone
(talus)

3. Articular
cartilage
Compact bone
Proximal
epiphysis
Spongy bone
Epiphyseal
line
Periosteum
Endosteum
Compact bone
Medullary
cavity (lined
by endosteum)
(b)
Yellow
bone marrow
Diaphysis
Compact bone
Periosteum
Perforating
(Sharpey’s)
fibers
Nutrient
arteries
Distal
epiphysis
(a)
(c)

4. Figure 6.3a The structure of a long bone (humerus of arm).
Articular
cartilage
Proximal epiphysis
Spongy bone
Epiphyseal line
Figure 6.3a The structure of a long bone (humerus of arm).
Periosteum
Compact bone
Medullary
cavity (lined
by endosteum)
Diaphysis
Distal epiphysis
(a)

5. Articular
cartilage
Compact bone
Spongy bone

6. Endosteum
Yellow
bone marrow
Compact bone
Periosteum
Perforating
(Sharpey’s) fibers
Nutrient
arteries

7. Figure 6.4 Comparison of different types of bone cells.
(a) Osteogenic cell
(b) Osteoblast
(c) Osteocyte
(d) Osteoclast
Figure 6.4 Comparison of different types of bone cells.
Stem cell
Matrix-synthesizing
cell responsible
for bone growth
Mature bone cell
that maintains the
bone matrix
Bone-resorbing cell

8. Spongy bone
(diploë)
Figure 6.5 Flat bones consist of a layer of spongy bone sandwiched between two thin layers of compact bone.
Compact
bone
Trabeculae

9. Figure 6.7 Microscopic anatomy of compact bone.
Spongy bone
Central
(Haversian) canal
Perforating
(Volkmann’s) canal
Figure 6.7 Microscopic anatomy of compact bone.
Endosteum lining bony canals
and covering trabeculae
Osteon
(Haversian system)
Circumferential
lamellae
(a)
Perforating (Sharpey’s) fibers
Lamellae
Periosteal blood vessel
Periosteum
Nerve
Vein
Artery
Lamellae
Central
canal
Canaliculi
Lacuna (with
osteocyte)
Osteocyte
in a lacuna
Lacunae
Interstitial lamellae
(b)
(c)

10. Figure 6.8 Intramembranous ossification.
Mesenchymal
cell
Osteoblast
Collagen
fiber
Osteoid
Ossification
center
Osteocyte
Newly calcified
bone matrix
Osteoid
Osteoblast
Figure 6.8 Intramembranous ossification. 1
Ossification centers appear in the fibrous
connective tissue membrane. 2
Bone matrix (osteoid) is secreted within the
fibrous membrane and calcifies.
• Selected centrally located mesenchymal cells cluster
and differentiate into osteoblasts, forming an
ossification center.
• Osteoblasts begin to secrete osteoid, which is calcified
within a few days.
• Trapped osteoblasts become osteocytes.
Mesenchyme
condensing
to form the
periosteum
Fibrous
periosteum
Osteoblast
Plate of
compact bone
Trabeculae of
woven bone
Diploë (spongy
bone) cavities
contain red
marrow
Blood vessel 3
Woven bone and periosteum form. 4
Lamellar bone replaces woven bone, just deep to
the periosteum. Red marrow appears.
• Accumulating osteoid is laid down between embryonic
blood vessels in a random manner. The result is a network
(instead of lamellae) of trabeculae called woven bone.
• Vascularized mesenchyme condenses on the external face
of the woven bone and becomes the periosteum.
• Trabeculae just deep to the periosteum thicken, and are later
replaced with mature lamellar bone, forming compact bone
plates.
• Spongy bone (diploë), consisting of distinct trabeculae, per-
sists internally and its vascular tissue becomes red marrow.

11. Figure 6.8 Intramembranous ossification (1 of 4).
Mesenchymal
cell
Collagen
fiber
Figure 6.8 Intramembranous ossification (1 of 4).
Ossification
center
Osteoid
Osteoblast
Ossification centers appear in the fibrous
connective tissue membrane.
• Selected centrally located mesenchymal cells cluster
and differentiate into osteoblasts, forming an
ossification center. 1

12. Figure 6.8 Intramembranous ossification (2 of 4).
Osteoblast
Osteoid
Figure 6.8 Intramembranous ossification (2 of 4).
Osteocyte
Newly calcified
bone matrix
Bone matrix (osteoid) is secreted within the
fibrous membrane and calcifies.
• Osteoblasts begin to secrete osteoid, which is calcified
within a few days.
• Trapped osteoblasts become osteocytes. 2

13. Figure 6.8 Intramembranous ossification (3 of 4).
Mesenchyme
condensing
to form the
periosteum
Trabeculae of
woven bone
Figure 6.8 Intramembranous ossification (3 of 4).
Blood vessel
Woven bone and periosteum form.
• Accumulating osteoid is laid down between embryonic
blood vessels in a random manner. The result is a network
(instead of lamellae) of trabeculae called woven bone.
• Vascularized mesenchyme condenses on the external face
of the woven bone and becomes the periosteum. 3

14. Figure 6.8 Intramembranous ossification (4 of 4).
Fibrous
periosteum
Osteoblast
Plate of
compact bone
Figure 6.8 Intramembranous ossification (4 of 4).
Diploë (spongy
bone) cavities
contain red
marrow
Lamellar bone replaces woven bone, just deep to
the periosteum. Red marrow appears.
• Trabeculae just deep to the periosteum thicken, and are later
replaced with mature lamellar bone, forming compact bone
plates.
• Spongy bone (diploë), consisting of distinct trabeculae, per-
sists internally and its vascular tissue becomes red marrow. 4

15. Figure 6.9 Endochondral ossification in a long bone.
Week 9
Month 3
Birth
Childhood to
adolescence
Articular
cartilage
Secondary
ossification
center
Spongy
bone
Epiphyseal
blood vessel
Figure 6.9 Endochondral ossification in a long bone.
Area of
deteriorating
cartilage matrix
Epiphyseal
plate
cartilage
Hyaline
cartilage
Medullary
cavity
Spongy
bone
formation
Bone
collar
Blood
vessel of
periosteal
bud
Primary
ossification
center
Bone collar
forms around
hyaline cartilage
model. 1
Cartilage in the
center of the
diaphysis calcifies
and then develops
cavities. 2
The periosteal
bud invades the
internal cavities
and spongy bone
begins to form. 3
The diaphysis elongates
and a medullary cavity
forms as ossification
continues. Secondary
ossification centers appear
in the epiphyses in
preparation for stage 5. 4
The epiphyses
ossify. When
completed, hyaline
cartilage remains only
in the epiphyseal
plates and articular
cartilages. 5

16. Resting zone
Proliferation zone
Cartilage cells undergo
mitosis. 1
Figure Growth in length of a long bone occurs at the epiphyseal plate.
Hypertrophic zone
Older cartilage cells
enlarge. 2
Calcification zone
Matrix becomes calcified;
cartilage cells die; matrix
begins deteriorating. 3
Calcified cartilage
spicule
Osteoblast depositing
bone matrix
Ossification zone
New bone formation is
occurring.
Osseous tissue
(bone) covering
cartilage spicules 4

17. Figure 6.11 Long bone growth and remodeling during youth.
Bone remodeling
Articular cartilage
Cartilage
grows here.
Figure Long bone growth and remodeling during youth.
Epiphyseal plate
Cartilage
is replaced
by bone here.
Bone is
resorbed here.
Cartilage
grows here.
Bone is added
by appositional
growth here.
Cartilage
is replaced
by bone here.
Bone is
resorbed here.

18. GIGANTISM

19. Figure 6.17 Fetal primary ossification centers at 12 weeks.
Parietal bone
Occipital bone
Frontal bone
of skull
Mandible
Figure Fetal primary ossification centers at 12 weeks.
Clavicle
Scapula
Radius
Ulna
Ribs
Humerus
Vertebra
Ilium
Tibia
Femur

20. Hematoma 1
A hematoma forms.

21. 2 External callus Internal New callus blood (fibrous vessels
tissue and
cartilage)
New
blood
vessels
Spongy
bone
trabecula 2
Fibrocartilaginous
callus forms.

22. Bony
callus of
spongy
bone 3
Bony callus forms.

23. Healed
fracture 4
Bone remodeling
occurs.

27. STRESS FRACTURE

28. Figure 6.12 Parathyroid hormone (PTH) control of blood calcium levels.
Calcium homeostasis of blood: 9–11 mg/100 ml
BALANCE
BALANCE
Stimulus
Falling blood
Ca2+ levels
Figure Parathyroid hormone (PTH) control of blood calcium levels.
Thyroid
gland
Osteoclasts
degrade bone
matrix and
release Ca2+
into blood.
Parathyroid
glands
Parathyroid
glands release
parathyroid
hormone (PTH).
PTH

30. TRACTION