The skeletal system chapter discusses the structure and function of the skeletal system. It describes how the skeleton is divided into the axial skeleton, which includes the skull, vertebral column, and rib cage, and the appendicular skeleton, which includes the limbs and their attachments. It details the types of bones, their microscopic structure, growth and remodeling, fractures and their repair. Joints are classified by function and structure. The functions of the skeletal system include support, protection, movement, mineral storage and blood cell formation.

1. CHAPTER 5
THE SKELETAL SYSTEM

2. The Skeletal System
 Parts of the skeletal system
 Bones (skeleton)
 Joints
 Cartilages
 Ligaments (bone to bone)(tendon=bone to
muscle)

3. The Skeletal System
 Divided into two divisions
 Axial skeleton
 Appendicular skeleton – limbs and girdle

4. Axial Skeleton
• Consists of 80 bones along
the central axis of the
human body
• It is composed of six parts;
the skull, the ossicles (in
middle ear), the hyoid
bone, the rib cage, the
sternum, and the vertebral
column

5. Appendicular Skeleton
• Composed of 126 bones in
the human body
• Appendicular is an
adjective derived from the
noun appendage
• This means that these
structures are joined to
something larger

8. Functions of Bones
 1. Support of the body
 2. Protection of soft organs
 3. Movement due to attached skeletal
muscles
 4. Storage of minerals and fats
 5. Blood cell formation

9. Functions of Bones
• 1. Support of the body
– Internal framework that supports the body and
cradles its soft organs
• 2. Protection of soft organs
– Ex. skull – brain, rib cage – lungs and heart

10. Functions of Bones
• 3. Movement due to attached skeletal muscles
– Skeletal muscles attached by tendons use the
bones as levers to move the body and its parts
• 4. Storage of minerals and fats
– Fat is stored in the internal cavities of bone
– Stores minerals such as calcium and phosphorus

11. Functions of Bones
• 5. Blood cell formation
– Hematopoiesis
– Occurs within the marrow cavities of certain
bones

12. Bones of the Human Body
 The skeleton has 206 bones
 Two basic types of bone tissue
Compact bone
 Homogeneous
Spongy bone
 Small needle-like
pieces of bone
 Many open spaces
Figure 5.2b

13. Classification of Bones on the
Basis of Shape
Figure 5.1

14. Classification of Bones
 Long bones
Typically longer
than they are wide
Have a shaft with
heads at both ends
Contain mostly
compact bone
• Examples:
Femur, humerus

15. Classification of Bones
 Short bones
Generally cube-
shape
Contain mostly
spongy bone
Examples: Carpals,
tarsals

16. Classification of Bones
 Flat bones
Thin and flattened
Usually curved
Thin layers of
compact bone
around a layer of
spongy bone
Examples: Skull,
ribs, sternum

17. Classification of Bones
 Irregular bones
Irregular shape
Do not fit into
other bone
classification
categories
Example:
Vertebrae and
hip

18. Gross Anatomy of a Long Bone
 Diaphysis
Shaft
Composed of
compact bone
 Epiphysis
Ends of the bone
Composed mostly of
spongy bone
Figure 5.2a

19. Gross Anatomy of a Long Bone

20. Structures of a Long Bone
 Periosteum
 Outside covering of
the diaphysis
 Fibrous connective
tissue membrane
 Sharpey’s fibers
 Secure periosteum to
underlying bone
 Arteries
 Supply bone cells
with nutrients
Figure 5.2c

21. Structures of a Long Bone

22. Structures of a Long Bone
 Articular cartilage
Covers the
external surface of
the epiphyses
Made of hyaline
cartilage
Decreases friction
at joint surfaces Figure 5.2a

23. Structures of a Long Bone
 Medullary cavity
Cavity of the shaft
Contains yellow
marrow (mostly fat)
in adults
Contains red marrow
(for blood cell
formation) in infants Figure 5.2a

24. Bone Marrow

27. Bone Markings - Page 138
Slide 5.9
 Surface features of bones
 Sites of attachments for muscles,
tendons, and ligaments
 Passages for nerves and blood
vessels
 Categories of bone markings
 Projections and processes –
grow out from the bone surface
 Depressions or cavities –
indentations

29. Microscopic Anatomy of Bone
 Osteon (Haversian System)
 A unit of bone
 Central (Haversian) canal
 Opening in the center of an
osteon
 Carries blood vessels and
nerves
 Perforating (Volkman’s) canal
 Canal perpendicular to the
central canal
 Carries blood vessels and
nerves

31. Microscopic Anatomy of Bone
Figure 5.3

32. Microscopic Anatomy of Bone
 Lacunae
 Cavities containing
bone cells
(osteocytes)
 Arranged in
concentric rings
 Lamellae
 Rings around the
central canal
 Sites of lacunae Figure 5.3

33. Microscopic Anatomy of Bone
 Canaliculi
Tiny canals
Radiate from the
central canal to
lacunae
Form a transport
system
Figure 5.3

34. Changes in 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
 Ears
 Parts of ribs
 Joints

35. Bone Growth
 Epiphyseal plates
allow for growth of
long bone during
childhood
 New cartilage is
continuously formed
 Older cartilage
becomes ossified
 Cartilage is broken
down
 Bone replaces
cartilage

37. Bone Growth
 Bones are remodeled and lengthened
until growth stops
Bones change shape somewhat
Bones grow in width

38. Long Bone Formation and Growth
Figure 5.4a

39. Types of Bone Cells
 Osteocytes
 Mature bone cells
 Osteoblasts
 Bone-forming cells
 Osteoclasts
 Bone-destroying cells
 Break down bone matrix for remodeling and
release of calcium
 Bone remodeling is a process by both
osteoblasts and osteoclasts

40. osteoblasts
osteocytes
osteoblasts

41. Bone Fractures
 A 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
 Bone fractures are treated by reduction
and immobilization
 Realignment of the bone

42. Common Types of Fractures
Table 5.2

43. Repair of Bone Fractures
• 1.Inflammation -
Hematoma (blood-filled
swelling) is formed
• Begins immediately after
the injury and lasts up to
5 days

44. Repair of Bone Fractures
• 2. Soft callus
formation - Break is
splinted by
fibrocartilage to form a
callus
• Begins anywhere from 4
day to 3 weeks after
injury, lasts about 6
weeks

45. Repair of Bone Fractures
• 3. Hard callus
formation -
Fibrocartilage callus
is replaced by a
bony callus
• Lasts 6-12 weeks; 6
for upper limbs, 12
for lower limbs

46. Repair of Bone Fractures
• 4. Bone remodeling
- Bony callus is
remodeled to form
a permanent patch
• Can continue for
several years

47. Stages in the Healing of a Bone
Fracture
Figure 5.5

48. The Axial Skeleton
 Forms the longitudinal part of the body
 Divided into six parts
 Skull
 Ossicles
 Hyoid bone
 Vertebral column
 Rib cage
 Sternum

49. The Axial Skeleton
Figure 5.6

50. The Skull
 Two sets of bones
Cranium
Facial bones
 Bones are joined by sutures
 Only the mandible is attached by a
freely movable joint

51. The Skull
Figure 5.7

52. Bones of the Skull
Figure 5.11

53. Human Skull, Superior View
Figure 5.8

54. Human Skull, Inferior View
Figure 5.9

55. Paranasal Sinuses
 Hollow portions of bones surrounding
the nasal cavity
Figure 5.10

56. Paranasal Sinuses
 Functions of paranasal sinuses
 Lighten the skull
 Give resonance and amplification to voice
Figure 5.10

57. The Hyoid Bone
 The only bone that
does not articulate
with another bone
 Serves as a
moveable base for
the tongue
Figure 5.12

58. The Fetal Skull
 The fetal skull is
large compared
to the infants
total body length
Figure 5.13

59. The Fetal Skull
 Fontanelles –
fibrous membranes
connecting the
cranial bones
 Allow the brain
to grow
 Convert to bone
within 24 months
after birth
Figure 5.13

60. The Vertebral Column
 Vertebrae
separated by
intervertebral discs
 The spine has a
normal curvature
 Each vertebrae is
given a name
according to its
location Figure 5.14

61. Structure of a Typical Vertebrae
Figure 5.16

62. The Bony Thorax
 Forms a
cage to
protect
major
organs
Figure 5.19a

63. The Bony Thorax
 Made-up of
three parts
Sternum
Ribs
Thoracic
vertebrae
Figure 5.19a

64. The Appendicular Skeleton
 Limbs (appendages)
 Pectoral girdle
 Pelvic girdle

65. The Appendicular Skeleton
Figure 5.6c

66. The Pectoral (Shoulder) Girdle
 Composed of two bones
Clavicle – collarbone
Scapula – shoulder blade
 These bones allow the upper limb to
have exceptionally free movement

67. Bones of the Shoulder Girdle
Figure 5.20a, b

68. Bones of the Upper Limb
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 The arm is
formed by a
single bone
Humerus
Figure 5.21a, b

69. Bones of the Upper Limb
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
• The forearm
has two bones
• Ulna
• Radius
Figure 5.21c

70. Bones of the Upper Limb
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 The hand
Carpals – wrist
Metacarpals –
palm
Phalanges –
fingers
Figure 5.22

71. Bones of the Pelvic Girdle
Slide 5.37Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Hip bones
 Composed of three pair of fused bones
 Ilium
 Ischium
 Pubic bone
 The total weight of the upper body rests on the
pelvis
 Protects several organs
 Reproductive organs
 Urinary bladder
 Part of the large intestine

72. The Pelvis
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 5.23a

73. Gender Differences of the Pelvis
Slide 5.39Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 5.23c

74. Bones of the Lower Limbs
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 The thigh has
one bone
Femur – thigh
bone
Figure 5.35a, b

75. Bones of the Lower Limbs
SlideCopyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 The leg has
two bones
Tibia
Fibula
Figure 5.35c

76. Bones of the Lower Limbs
Slide 5.41Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 The foot
Tarsus – ankle
Metatarsals –
sole
Phalanges –
toes
Figure 5.25

77. Joints
Slide 5.43Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Articulations of bones
 Functions of joints
Hold bones together
Allow for mobility
 Ways joints are classified
Functionally
Structurally

78. Functional Classification of Joints
Slide 5.44Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Synarthroses – immovable joints
 Amphiarthroses – slightly moveable
joints
 Diarthroses – freely moveable joints

79. Structural Classification of Joints
Slide 5.45Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Fibrous joints
Generally immovable
 Cartilaginous joints
Immovable or slightly moveable
 Synovial joints
Freely moveable

80. Fibrous Joints
Slide 5.46Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Bones united by fibrous tissue –
synarthrosis or largely immovable.
Figure 5.27d, e

81. Cartilaginous Joints – mostly
amphiarthrosis
Slide 5.47Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
 Bones connected by cartilage
 Examples
Pubic
symphysis
Intervertebral
joints
Figure 5.27b, c

82. Synovial Joints
 Articulating
bones are
separated by a
joint cavity
 Synovial fluid
is found in the
joint cavity
Figure 5.27f–h

83. Features of Synovial Joints-
Diarthroses
 Articular cartilage (hyaline cartilage)
covers the ends of bones
 Joint surfaces are enclosed by a fibrous
articular capsule
 Have a joint cavity filled with synovial
fluid
 Ligaments reinforce the joint

84. Structures Associated with the
Synovial Joint
 Bursae – flattened fibrous sacs
 Lined with synovial membranes
 Filled with synovial fluid
 Not actually part of the joint
 Tendon sheath
 Elongated bursa that wraps around a tendon

85. The Synovial Joint
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 5.28

86. Types of Synovial Joints Based on
Shape
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Figure 5.29a–c

87. Types of Synovial Joints Based on
Shape
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 5.29d–f

88. 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
 The most widespread crippling disease in the
United States

89. Clinical Forms of Arthritis
 Osteoarthritis
 Most common chronic arthritis
 Probably related to normal aging processes
 Rheumatoid arthritis
 An autoimmune disease – the immune system
attacks the joints
 Symptoms begin with bilateral inflammation of
certain joints
 Often leads to deformities

92. Clinical Forms of Arthritis
 Gouty Arthritis
Inflammation of joints is caused by a
deposition of urate crystals from the blood
Can usually be controlled with diet