Chapter 6:
Skeletal System I
Bernard Siegfried Albinus 1697 – 1770
Famous for his drawings in the work entitled
Tables of the Skeleton and Muscles
of the Human Body
published in 1747.
An example of Albinus’ drawings of the skeleton.
Figure 6.1 The bones and cartilages of the human skeleton.
Cartilage in
external ear
Cartilage in
Intervertebral
disc
Cartilages in
nose
Articular
Cartilage
of a joint
Epiglottis
Thyroid
cartilage
Cricoid
cartilage
Larynx
Trachea
Lung
Costal
cartilage
Respiratory tube cartilages
in neck and thorax
Pubic
symphysis
Meniscus
(padlike
cartilage in
knee
joint)
Articular
cartilage
of a joint
Bones of skeleton
Axial skeleton
Appendicular skeleton
Cartilages
Hyaline cartilages
Elastic cartilages
Fibrocartilages
Figure 6.2 Classification of bones on the basis of shape.
(a) Long bone
(humerus)
(b) Irregular bone
(vertebra), right
lateral view
(c) Flat bone
(sternum)
(d) Short bone
(talus)
Figure 6.3a The structure of a long bone (humerus of arm).
Articular
cartilage
Proximal epiphysis
Spongy bone
Epiphyseal line
Periosteum
Compact bone
Medullary
cavity (lined
by endosteum)
Diaphysis
Distal epiphysis
(a)
Figure 6.3b The structure of a long bone (humerus of arm).
Articular
cartilage
Compact bone
Spongy bone
(b)
Figure 6.3c The structure of a long bone (humerus of arm).
Endosteum
Yellow
bone marrow
Compact bone
Periosteum
Perforating
(Sharpey’s) fibers
Nutrient
arteries
(c)
Figure 6.4 Comparison of different types of bone cells.
(a) Osteogenic cell
(b) Osteoblast
(c) Osteocyte
(d) Osteoclast
Stem cell
Matrix-synthesizing
cell responsible
for bone growth
Mature bone cell
that maintains the
bone matrix
Bone-resorbing cell
Figure 6.5 Flat bones consist of a layer of spongy bone sandwiched between two thin layers of compact bone.
Spongy bone
(diploë)
Compact
bone
Trabeculae
Figure 6.9 Endochondral ossification in a long bone.
Month 3
Week 9
Birth
Childhood to
adolescence
Articular
cartilage
Secondary
ossification
center
Epiphyseal
blood vessel
Area of
deteriorating
cartilage matrix
Hyaline
cartilage
Spongy
bone
formation
Bone
collar
Primary
ossification
center
1 Bone collar
Spongy
bone
Epiphyseal
plate
cartilage
Medullary
cavity
Blood
vessel of
periosteal
bud
2 Cartilage in the
3 The periosteal
center of the
forms around
hyaline cartilage diaphysis calcifies
and then develops
model.
cavities.
bud invades the
internal cavities
and spongy bone
begins to form.
4 The diaphysis elongates
and a medullary cavity
forms as ossification
continues. Secondary
ossification centers appear
in the epiphyses in
preparation for stage 5.
5 The epiphyses
ossify. When
completed, hyaline
cartilage remains only
in the epiphyseal
plates and articular
cartilages.
Figure 6.11 Long bone growth and remodeling during youth.
Bone growth
Cartilage
grows here.
Bone remodeling
Articular cartilage
Epiphyseal plate
Cartilage
is replaced
by bone here.
Cartilage
grows here.
Cartilage
is replaced
by bone here.
Bone is
resorbed here.
Bone is added
by appositional
growth here.
Bone is
resorbed here.
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
Thyroid
gland
Osteoclasts
degrade bone
matrix and
release Ca2+
into blood.
Parathyroid
glands
PTH
Parathyroid
glands release
parathyroid
hormone (PTH).
Calcitonin
Figure 6.13 Bone anatomy and bending stress.
Load here (body weight)
Head of
femur
Tension
here
Compression
here
Point of
no stress
Figure 6.14 Vigorous exercise can lead to large increases in bone strength.
(a)
(b) Serving arm
Crosssectional
dimension of
the humerus
Added
bone matrix
counteracts
added stress
Nonserving arm
Steel “Bone Cages” used to lengthen legs. These were originally
developed in the Soviet Union in the 1950s to treat dwarfism.
Twelve-year-old boy with pituitary gigantism measuring 6'5"
with his mother. Note the coarse facial features and
prominent jaw.
An example of untreated acromegaly.
Chelation Therapy – intravenous administration
of chemicals designed to absorb toxic
substances that have accumulated in the body.
Most notably used for exposure to heavy metals
such as lead or mercury.
Figure 6.15 Stages in the healing of a bone fracture.
Hematoma
Internal
callus
(fibrous
tissue and
cartilage)
1 A hematoma forms.
External
callus
New
blood
vessels
Bony
callus of
spongy
bone
Healed
fracture
Spongy
bone
trabecula
2 Fibrocartilaginous
callus forms.
3 Bony callus forms.
4 Bone
remodeling
occurs.
Figure 6.16 The contrasting architecture of normal versus osteporotic bone.
Figure UN 6.1
Figure 6.17 Fetal primary ossification centers at 12 weeks.
Parietal bone
Occipital bone
Mandible
Frontal bone
of skull
Clavicle
Scapula
Radius
Ulna
Ribs
Humerus
Vertebra
Ilium
Tibia
Femur
Table 6.2 Common Types of Fractures (1 of 3)
Table 6.2 Common Types of Fractures (2 of 3)
Table 6.2 Common Types of Fractures (3 of 3)