1. Skeletal System
Chapter 5

2. The Skeletal System Parts of the skeletal system
Bones (skeleton)
Joints
Cartilages
Ligaments
Two subdivisions of the skeleton
Axial skeleton
Appendicular skeleton

3. Functions of Bones Support the body Protect soft organs
Acts as a lever for attached skeletal muscles
Store minerals and fats
Blood cell formation (hematopoiesis)

4. Bones of the Human Body The adult skeleton has 206 bones
Two basic types of bone tissue
Compact bone
Spongy bone

5. Anatomy of a Long Bone Diaphysis Shaft Composed of compact bone
Epiphysis
Ends of the bone
Composed mostly of spongy bone
Figure 5.3a
Distal
epiphysis
Diaphysis
Proximal
Articular
cartilage
Spongy bone
Epiphyseal
line
Periosteum
Compact bone
Medullary
cavity (lined
by endosteum)
(a)

6. Anatomy of a Long Bone Periosteum
Fibrous connective tissue membrane, covers outside of the diaphysis
Perforating (Sharpey’s) fibers
Hyaline cartilage lines joint surfaces
Arteries
Endosteum
Yellow
bone marrow
Compact bone
Periosteum
Perforating
(Sharpey’s)
fibers
Nutrient
arteries
(c)
Figure 5.3c

7. Anatomy of a Long Bone Epiphyseal line (Adults)
Figure 5.3a
Distal
epiphysis
Diaphysis
Proximal
Articular
cartilage
Spongy bone
Epiphyseal
line
Periosteum
Compact bone
Medullary
cavity (lined
by endosteum)
(a)
Epiphyseal plate (Young)
Flat plate of hyaline cartilage
Epiphyseal line (Adults)
Remnant of the epiphyseal plate

8. Anatomy of a Long Bone Marrow (medullary) cavity
Contains yellow marrow (mostly fat) in adults
Infants: red marrow for blood cell formation
In adults: red marrow is cavities of spongy bone

9. Microscopic Anatomy of Compact Bone
Osteon (Haversian system)
Central canal and matrix rings
Carries blood vessels and nerves
Perforating (Volkmann’s) canal

10. Osteon
(Haversian system)
Lamellae
Blood vessel continues into
medullary cavity containing marrow
Spongy bone
Perforating
fibers
Compact
bone
Periosteal
blood vessel
Central (Haversian) canal
Periosteum
Perforating
(Volkmann’s) canal
(a)
Blood vessel
Figure 5.4a

11. Microscopic Anatomy of Bone
Lacunae
Cavities containing bone cells (osteocytes)
Arranged in concentric rings called lamellae
Lamellae
Calcified cartilage surrounding lacunae

12. Formation of the Human Skeleton
In embryos, the skeleton is primarily hyaline cartilage
During development, much of this cartilage is replaced by bone
Cartilage remains in isolated areas
Bridge of the nose
Parts of ribs
Joints

13. Bone Growth (Ossification)
Epiphyseal plates allow for lengthwise growth of long bones during childhood
New cartilage is continuously formed
Older cartilage becomes ossified
Cartilage is broken down
Enclosed cartilage is digested away, opening up a medullary cavity
Bone replaces cartilage through the action of osteoblasts

14. Bone Growth (Ossification)
Bones are remodeled and lengthened until growth stops
Bones are remodeled in response to two factors
Blood calcium levels
Pull of gravity and muscles on the skeleton
Bones grow in width (called appositional growth)

15. Articular cartilage Hyaline cartilage Spongy bone New center of
bone growth
New bone
forming
Epiphyseal
plate
cartilage
Growth
in bone
width
Medullary
cavity
Bone starting
to replace
cartilage
Invading
blood
vessels
Growth
in bone
length
New bone
forming
Bone collar
Hyaline
cartilage
model
Epiphyseal
plate cartilage
In an embryo
In a fetus
In a child
Figure 5.5

16. is replaced by bone here. 4 Bone is resorbed here. 3
Bone growth
Bone remodeling
Bone grows in
length because:
Growing shaft is
remodeled as:
Articular cartilage
Cartilage
grows here. 1
Epiphyseal plate
Cartilage
is replaced
by bone here. 2 1
Bone is
resorbed here.
Cartilage
grows here. 3 2
Bone is added
by appositional
growth here.
Cartilage
is replaced by bone here. 4
Bone is
resorbed here. 3
Figure 5.6

17. Bone Remodeling Osteocytes are mature bone cells
Osteoclasts digest organic matric in response to PTH
Increases blood calcium levels
Osteoblasts form organic matric in response to calcitonin
Decrease blood calcium levels
Mechanical and gravitational forces also affect remodeling 17 17

18. Bone Remodeling
Balance between resorption and formation 18 18

19. Bone Fractures Fracture—break in a bone Types of bone fractures
Closed (simple) fracture—break that does not penetrate the skin
Open (compound) fracture—broken bone penetrates through the skin

20. Common Types of Fractures
Comminuted—bone breaks into many fragments
Compression—bone is crushed
Depressed—broken bone portion is pressed inward
Impacted—broken bone ends are forced into each other
Spiral—ragged break occurs when excessive twisting forces are applied to a bone
Greenstick—bone breaks incompletely

21. Figure 5.7 Hematoma External callus Bony callus of spongy bone New
blood
vessels
Internal
callus
(fibrous
tissue and
cartilage)
Healed
fracture
Spongy
bone
trabecula
Hematoma
forms. 1
Fibrocartilage
callus forms. 2
Bony callus
forms. 3
Bone remodeling
occurs. 4
Figure 5.7

22. Inflammatory Conditions Associated with Joints
Bursitis—inflammation of a bursa usually caused by a blow or friction
Tendonitis—inflammation of tendon sheaths
Arthritis—inflammatory or degenerative diseases of joints
Over 100 different types
Autoimmune disease

23. Clinical Forms of Arthritis
Osteoarthritis
Most common chronic arthritis, related to normal aging processes
Rheumatoid arthritis
An autoimmune disease—the immune system attacks the joints
Gouty arthritis
Deposition of uric acid crystals from the blood

24. Figure 5.33