1. UNIT 3
Skeletal System

2. Introduction A. Bones are very active tissues.
B. Each bone is made up of several types of tissues and so is an organ.
C. Bone functions include:
- muscle attachment
- protection and support
- blood cell production
- storage of minerals

3. Bone Structure
A.Bones differ in size and shape, yet are similar in several ways.
B.Parts of a Long Bone
1. Epiphyses
2. Articular cartilages
3. Diaphysis
4. Periosteum
5. Compact Bone
6. Spongy Bone
7. Endosteum (Marrow)

5. Epiphyses - Expanded ends of bones that form joints with adjacent bones

6. Epiphyses - Expanded ends of bones that form joints with adjacent bones
Articular cartilage - (hyaline cartilage) cover the epiphyses.

7. Epiphyses - Expanded ends of bones that form joints with adjacent bones
Diaphysis - shaft of the bone
Articular cartilage - (hyaline cartilage) cover the epiphyses.

8. Epiphyses - Expanded ends of bones that form joints with adjacent bones
Diaphysis - shaft of the bone
Periosteum - tough layer of vascular connective tissue that covers the bone
Articular cartilage - (hyaline cartilage) cover the epiphyses.

9. Spongy Bone – fills the epiphyses, porous to reduce the weight of the skeleton.
Epiphyses - Expanded ends of bones that form joints with adjacent bones
Diaphysis - shaft of the bone
Periosteum - tough layer of vascular connective tissue that covers the bone
Articular cartilage - (hyaline cartilage) cover the epiphyses.

10. Spongy Bone – fills the epiphyses, porous to reduce the weight of the skeleton.
Epiphyses - Expanded ends of bones that form joints with adjacent bones
Compact bone - makes up the wall of the diaphysis
Diaphysis - shaft of the bone
Periosteum - tough layer of vascular connective tissue that covers the bone
Articular cartilage - (hyaline cartilage) cover the epiphyses.

11. Spongy Bone – fills the epiphyses, porous to reduce the weight of the skeleton.
Epiphyses - Expanded ends of bones that form joints with adjacent bones
Compact bone - makes up the wall of the diaphysis
Diaphysis - shaft of the bone
Periosteum - tough layer of vascular connective tissue that covers the bone
Articular cartilage - (hyaline cartilage) cover the epiphyses.
Bony Process – grooves in the bone where muscles attach

13. Bone Structure C. Classification of Bones
Bones are classified according to following shapes:
Long
Short
Flat
Irregular
Sesamoid

14. Microscopic Cross-Section of Bone

15. Bone Structure D. Microscopic Structure
1. Bone cells (osteocytes) are located within lacunae that lie in concentric circles around osteonic (central) canals.

16. Bone Structure
2. Osteocytes pass nutrients and gasses in the matrix through canaliculi.
The bone cells can function because of the canaliculi! They supply what the cell needs!

17. The arrangement of bone cells effect the type of bone.
 Cemented bone cells create compact bone
- the organization of these cells create a “central canal” where nerve and blood vessels pass through
 Spongy bone lacks this organization
central canal

20. Bone Development and Growth

21. Bone Growth Ossification – the formation of bone
This process uses specialized cells.
Osteocytes – living bone cells
Osteoblasts – bone builders – create osteocyte
Osteoclasts – bone breakers – destroy osteocyte

22. Bone Development & Growth
A. Bones form by replacing connective tissues in the fetus.
Babies are born with over 300 bones. At adulthood, the number of bones in the body in 206 (teeth depending).
In the fetal skeleton – bones fuse together as growth occurs.

23. Bone Development & Growth
B. Some bones form within sheetlike layers of connective tissue (intramembranous bones), while others replace masses of cartilage (endochondral bones). 23 23

24. Bone Development & Growth
C. Intramembranous Bones
1. The flat bones of the skull form as intramembranous bones that develop from layers of connective tissue.
2. Osteoblasts deposit bony tissue around themselves.
All of this happens under a membrane –
Hence “intra” “membranous” 24 24

25. Bone Development & Growth
3. Once osteoblasts deposit bone are located in lacunae, they are called osteocytes.
Osteoblast (before)  Osteocyte (after)

27. Bone Development & Growth
D. Endochondral Bones
1. Most of the bones of the skeleton fall into this category.
2. They first develop as hyaline cartilage models and are then replaced with bone.

28. Bone Development & Growth
3. Cartilage is broken down in the diaphysis and progressively replaced with bone while the periosteum develops on the outside.
4. Cartilage tissue is invaded by blood vessels and osteoblasts.
but where does the cartilage go?
NOTE: Cartilage does not contain blood vessels 28 28

29. Bone Development & Growth
5. Osteoclasts break down the cartilage and are replaced with bone building osteoblasts that deposit bone in it’s place.

30. Bone Development & Growth
6. Epiphyseal plates are responsible for lengthening bones while increases in thickness are due to ossification underneath the periosteum.

32. The Taboo of Bones
Bones can also be manipulated in their growth – they can be enlongated, thinned, or thickened.

34. The Taboo of Bones
Because of the bone cells, when a bone breaks, it heals back stronger.

35. Bone Formation

36. Bone Function and Organization

37. A. Support and Protection
1. Bones give shape to the head, thorax, and limbs.
2. Bones such as the pelvis and lower limbs provide support for the body.
3. Bones of the skull protect the brain, ears, and eyes.

38. B. Bone Movement 1. Bones can act as levers.
a. A lever has four components:
- a rigid bar,
- a pivot or fulcrum,
- an object that is moved against resistance
- a force that supplies energy.

40. C. Blood Cell Formation
1. Blood cells are manufactured in bone marrow.
2. Two kinds of marrow occupy the medullary cavities of bone.

41. C. Blood Cell Formation
a. Red marrow functions in the formation of red blood cells, white blood cells, and platelets, and is found in the spongy bone of the skull, ribs, sternum, clavicles, vertebrae, and pelvis.

42. C. Blood Cell Formation
b. Yellow marrow, occupying the cavities of most bones, stores fat.

43. D. Storage of Inorganic Salts
1. The inorganic matrix of bone stores inorganic mineral salts in the form of calcium phosphate that is important in many metabolic processes. 43 43

44. D. Storage of Inorganic Salts
2. Calcium in bone is a reservoir for body calcium; when blood levels are low, osteoclasts release calcium from bone.
3. Calcium is stored in bone under the influence of calcitonin when blood levels of calcium are high.
Mr. T says
“DRINK YOUR MILK”
fool.
Homeostasis

46. D. Storage of Inorganic Salts
4. Bone also stores magnesium, sodium, potassium, and carbonate ions.
5. Bones can also accumulate harmful elements, such as lead, radium, and strontium. 46 46

47. Skeletal Organization
A. The axial skeleton consists of the:
- skull
- hyoid bone
- vertebral column (vertebrae and intervertebral disks)
- thorax (ribs and sternum)

48. Skull

49. Hyoid Bone

50. Vertrebral Column

51. Sternum and Ribs (Thorax)

52. Skeletal Organization
B. The appendicular skeleton consists of the:
- pectoral girdle (scapulae and clavicles)
- upper limbs (humerus, radius, ulna, carpals, metacarpals, and phalanges)
- pelvic girdle (coxal bones articulating with the sacrum)
- lower limbs (femur, tibia, fibula, patella, tarsals, metatarsals, phalanges)

53. Pectoral Gircle

54. Upper Limb

55. Pelvic Girdle

56. Lower Limb

58. Bones Summary Video

59. The body’s natural helmet.
The Skull
The body’s natural helmet.

60. Skull VIDEO

63. A Closer Look At….
The Maxilla

64. 64 64

66. A Closer Look At….
The Nasal Bone

67. 67 67

69. A Closer Look At….
The Zygomatic Bone

70. 70 70

72. A Closer Look At….
The Sphenoid Bone

73. 73 73

75. A Closer Look At….
The Frontal Bone

78. A Closer Look At….
The Temporal Bone

79. 79 79

81. A Closer Look At….
The Parietal Bone

82. 82 82

84. A Closer Look At….
The Occipital Bone

85. 85 85

88. The Joints of the Skeletal System

89. Joints
1. Joints (articulations) are the functional junctions between bones.
2. Joints enable a wide variety of body movements.
3. Joints can be classified according to the degree of movement possible and can be immovable, slightly movable, or freely movable.

90. Fibrous and Cartilaginous Joints
4. Joints can also classified according to the type of tissue that binds them together.
A. Fibrous Joints- held close together by dense connective tissue and are immovable
B. Cartilaginous Joints - help absorb shock and are slightly movable.

92. Synovial Joints C. Synovial Joints
1. Most joints of the skeleton are synovial joints.
2. The ends of bone in a synovial joint are covered with hyaline cartilage.

93. Synovial Joints
3. A joint capsule consists of an outer layer of dense connective tissue that joins the periosteum, and an inner layer made up of synovial membrane.
a. Synovial fluid has the consistency of egg whites and lubricates articulating surfaces within the joint.

94. Synovial Joints
4. Some synovial joints contain shock-absorbing pads of fibrocartilage called menisci.

97. Types of Synovial Joints
Type Of Joint
What It Looks Like
How It Moves
Where It Is
Ball and Socket
Circular motion, wide rage
Hip and Shoulder

98. Types of Synovial Joints
Type Of Joint
What It Looks Like
How It Moves
Where It Is
Condyloid
Single plane, wide rage
Metacarpal and Phalenge 98 98

99. Types of Synovial Joints
Type Of Joint
What It Looks Like
How It Moves
Where It Is
Gliding Joint
Rotate and twist – wide range
Wrist, ankle, vertebrae 99 99

100. Types of Synovial Joints
Type Of Joint
What It Looks Like
How It Moves
Where It Is
Saddle
Wide range
metacarpal
100
100

101. Types of Synovial Joints
Type Of Joint
What It Looks Like
How It Moves
Where It Is
Hinge
Back and forth, one plane, like a door hinge
Knee and elbow joints
101
101

102. Types of Synovial Joints
Type Of Joint
What It Looks Like
How It Moves
Where It Is
Pivot
Rotation
Head and Neck
102
102

104. Types of Joint Movements
1. When a muscle contracts, its fibers pull its movable end (insertion) toward its stationary end (origin), causing movement at a joint.

105. Types of Joint Movement
These terms describe movements that occur at joints:
flexion, extension, hyperextension

107. Types of Joint Movement
These terms describe movements that occur at joints:
dorsiflexion, plantar flexion

109. Types of Joint Movement
These terms describe movements that occur at joints:
abduction, adduction

111. Types of Joint Movement
These terms describe movements that occur at joints:
rotation, circumduction

113. Types of Joint Movement
These terms describe movements that occur at joints:
pronation, supination

115. Types of Joint Movement
These terms describe movements that occur at joints:
eversion, inversion

116. Types of Joint Movement
These terms describe movements that occur at joints:
retraction, protraction

117. Types of Joint Movement
These terms describe movements that occur at joints:
elevation, depression