1. The Skeletal System

2. Divisions of the Skeletal System
The human skeletal system is divided into two major divisions
Axial Skeleton
Appendicular skeleton

3. Axial Skeleton
The axial skeleton contains the bones of the head, neck, and torso (80 bones total)

4. appendicular skeleton
The appendicular skeleton contains the bones of the upper and lower extremities (126 bones total)

5. Human Skeleton
The human skeleton has a total of 206 bones in all

6. Bones Functions: Support Protection Movement Storage
Blood cell formation

7. Bones Function- Support
Form the internal framework that supports and anchors all soft organs

8. Bones Function- Protection Bones protect soft body organs
Ex. Skull protects brain

9. Bones Function- Movement Skeletal Muscles attach to bones by tendons
Bones are used as levers to move body

10. Bones
Functions-storage
Fat is stored in internal cavities of bones

11. Bones Functions-storage Store minerals
Most important—Calcium and phosphorus

12. Bones Functions-storage
Calcium in its ion form (Ca 2+ ) must always be present in blood
for nervous system to transmit messages
For muscles to contract
For blood to clot
Bones are a storage place for Calcium

13. Bones Functions-storage Blood cell formation
Hematopoiesis (formation of blood cells) occurs in the cavities of bone marrow

14. Bones Classification of bones 2 basic types of bone types Compact Bone
Spongy Bone

15. Bones
Compact Bone
Dense
Looks smooth

16. Bones
Spongy Bone
Small needle-like pieces of bone
Lots of open space

18. Shapes of Bones
Long Bones
Short Bones
Irregular Bones

19. Bones Long Bones Longer than they are wide
Usually have a shaft with heads at both ends
Mostly compact bones
most bones of limbs

20. Bones Short Bones Generally cube-shaped Mostly spongy bone
Ex. Patella (knee cap) , bones of wrist and ankle

21. Flat Bones Thin, flattened, usually curved
Two thick layers of compact bone sandwiching a layer of spongy bone
Bones of skull, ribs, sternum

22. Irregular Bones
Don’t fit other categories
Ex. Vertebrate, hip bone

23. Structure of a long bone
Diaphysis-
Shaft
Makes up most of the bone’s length
Composed of compact bone
Covered and protected by periosteum

24. Structure of a long bone
Cavity of shaft
In infants- this area forms blood cells
Red marrow
In adults primarily filled with yellow marrow (adipose)
Called yellow marrow cavity or medullary cavity
Red marrow is confined to spongy bone

25. Structure of a long bone
Epiphyses- the ends of the long bone
Epiphyseal line
Thin line spanning the epiphysis

26. Structure of a long bone
Epiphyseal plate
Plate of hyaline cartilage
Causes the lengthwise growth of a long bone
By end of puberty the plate is completely replaced by bone

27. Structure of Long Bone Surfaces of bones aren’t smooth Bone markings
Bumps, holes, and ridges
Bone markings
Reveal where muscles, tendons, and ligaments were attached
Reveal where blood vessels and nerves passed
Occipital bone marking

28. Structure of Long Bone Bone markings Projections or processes-
Grow out from the bone surface
Depressions or cavities
Indentations in the bone
Eye cavity

29. Structure of a long Microscopic anatomy Compact bone:
To the naked eye looks very dense
With microscope we see a much different picture!

30. Structure of a long Microscopic anatomy Compact bone
Passageways carrying nerves and blood vessels
Provides living bone with nutrients and route for waste disposal

31. Structure of Long Bone Osteocytes The mature bone cells
Found in cavities of the bone matrix called lacunae ( a very tough matrix)

32. Structure of Long Bone Osteocytes
Lacunae arranged in concentric circles called lamellae
Lacunae arranged around central (Haversian) canals

33. Structure of Long Bone Perforating (Volkmann’s) canals
Run into the compact bone at right angles to the shaft
Let the inside of bone communicate with outside

34. Bone Formation, Growth, and Remodeling
Embryo’s skeleton
Primarily hyaline cartilage
Young child
Most of cartilage has been replaced by bone
Remains in isolated areas
Bridge of nose
Parts of ribs
joints

35. Bone Formation, Growth, and Remodeling
Most bones develop using hyaline cartilage structures as their “models”
Ossification- the formation of bone

36. Bone Formation, Growth, and Remodeling
Ossification
2 major stages
1. hylane cartilage model is completely covered with bone by bone forming cells called osteoblasts

37. Bone Formation, Growth, and Remodeling
Ossification
Step Two:
Hyaline cartilage model is digested away
Opens up a medullary cavity within newly formed bone

38. Bone Formation, Growth, and Remodeling
By birth
Most hyaline cartilage models have been converted to bone
Excepts two reasons
Articular cartilages –cover bone ends
Epiphyseal plates

39. Bone Formation, Growth, and Remodeling
Articular cartilages
Persist for life
Reduce friction at the joint surfaces

40. Bone Formation, Growth, and Remodeling
How is the articular cartilage injured?
Trauma- twisting, sport injury
Certain diseases
Gradually over time

41. Bone Formation, Growth, and Remodeling
When there is significant loss of the articular cartilage, the knee is considered to have “arthritis”.

42. Bone Formation, Growth, and Remodeling
Epiphyseal plates
Provide for longitudinal growth of long bones during childhood
New cartilage is formed on external surface
Old cartilage is broken down and replaced by bony matrix

43. Bone Formation, Growth, and Remodeling
Epiphyseal plates
Growth controlled by hormones
Ends during adolescence, when the epiphyseal plates are completely converted to bone

44. Bone Formation, Growth, and Remodeling
How do bones widen? –called Appositional Growth
Osteoblasts in the periosteum add bone to the external face
Osteoclasts in the endosteum remove bone from inner wall

45. What happens when long bone growth ends?

46. Bone Formation, Growth, and Remodeling
Bone Remodeling
Bones continually remodeled in response to 2 factors:
1. calcium levels in the blood
2. the pull of gravity and muscles on the skeleton

47. Bone Formation, Growth, and Remodeling
Bone Remodeling
When blood calcium levels are low
Parathyroid hormone (PTH) is released into blood
PTH activates osteoclasts (bone destroying cells) to break down bone matrix and release calcium

48. Bone Formation, Growth, and Remodeling
Bone Remodeling
When blood calcium levels are too high (hypercalcemia)
Calcium is deposited in bone matrix as hard calcium salts

49. Bone Formation, Growth, and Remodeling
Bone Remodeling
Essential for bones to:
retain normal proportions
Strengthen as body increases size and weight

50. Bone Formation, Growth, and Remodeling
Bone Remodeling
Bedridden or physically inactive people tend to lose bone mass and atrophy
Because they aren’t subjected to stress

51. Bone Formation, Growth, and Remodeling
Rickets
Disease of children in which bones fail to calcify
Bones soften and definite bowing of weight-bearing bones of legs occurs

52. Bone Formation, Growth, and Remodeling
Rickets—
Called osteomalacia in adults
Causes
Usually due to lack of calcium in diet
Or lack of vitamin D
Is needed to absorb calcium

53. Divisions of the Skeletal System
Axial

54. Bones of the Axial Skeleton
Bones of the axial skeleton are divided into four major groups
Bones of the Skull
Hyoid Bone
Bones of the Spinal Column
Sternum and Ribs

55. Bones of the Axial Skeleton
Bones of the Skull (28 total)
Cranial Bones (8 total) form the cranium which surrounds the brain

56. Bones of the Axial Skeleton
Bones of the Skull (28 total)
Cranial Bones
1) Frontal Bone (1 bone)
Anterior Portion of Cranium (Forehead)
Forms Anterior Cranial Floor
Forms the Roofs of Orbits (Eye Sockets)

57. Bones of the Axial Skeleton
Bones of the Skull (28 total)
Cranial Bones
2) Parietal Bone (2 bones)
Forms Superior Portion of Cranium

58. Bones of the Axial Skeleton
Bones of the Skull (28 total)
Cranial Bones
3) Temporal Bone (2 bones)
Forms Lateral Portion of Cranium & Lateral Cranial Floor

59. Bones of the Axial Skeleton
Bones of the Skull (28 total)
Cranial Bones
4) Occipital Bone (1 bone)
Forms Posterior Portion of Cranium & Posterior Cranial Floor

60. Bones of the Axial Skeleton
Bones of the Skull (28 total)
Cranial Bones
5) Sphenoid Bone (1 bone)
Forms central portion of
cranial floor
Known as the “keystone of
the cranium” because
the sphenoid bone
anchors all the other
cranial bones

61. Bones of the Axial Skeleton
Bones of the Skull (28 total)
Cranial Bones
6) Ethmoid Bone (1 bone)
Complex, irregularly shaped bone found between the nasal and the sphenoid bones

62. Bones of the Axial Skeleton
Bones of the Skull (28 total)
Facial Bones
1) Nasal Bone (2 bones)
Forms the bridge of the nose

63. Bones of the Axial Skeleton
Bones of the Skull (28 total)
Facial Bones
2) Maxillary bone (2 Bones)
Upper jawbone that forms the central portion of the face
Forms the floor of the orbits and the anterior portion of the hard palate

64. Bones of the Axial Skeleton
Bones of the Skull (28 total)
Facial Bones
3) Zygomatic Bone (2 Bones)
Forms the cheekbones and
the lateral walls of the
orbits

65. Bones of the Axial Skeleton
Bones of the Skull (28 total)
Facial Bones
4) Mandible Bone (1 Bone)
Lower jawbone
Largest and strongest bone of the face

66. Bones of the Axial Skeleton
Bones of the Skull (28 total)
Facial Bones
5) Lacrimal Bone (2 Bones)
Forms the medial walls
of the orbits
Bones are paper thin

67. Bones of the Axial Skeleton
Bones of the Skull (28 total)
Facial Bones
6) Palatine Bone (2 Bones)
Forms posterior portion of the hard palate and forms the lateral and posterior walls of the nasal cavity

68. Bones of the Axial Skeleton
Bones of the Skull (28 total)
Facial Bones
8) Vomer Bone (1 Bone)
Forms the lower portion of the nasal septum

69. Bones of the Axial Skeleton
Bones of the Skull (28 total)
Bones of the Ear
Three tiny bones located in the middle ear
1) Malleus (2 Bones)
2) Incus (2 Bones)
3) Stapes (2 Bones)

70. Bones of the Axial Skeleton
Bones of the Skull (28 total)
Bones of the Ear
Smallest bones in the body
Carry sound vibrations to inner ear
Amplifies sound about 7x

71. Bones of the Axial Skeleton
Hyoid Bone (1 total)
The hyoid bone is a U shaped bone found in the neck between the mandible and the larynx
It is the only bone in the body which does not form a joint with another bone (held in place by ligaments and muscles)

72. Bones of the Axial Skeleton
Hyoid Bone (1 total)
Function:
Supports the base of the tongue

73. Bones of the Axial Skeleton
Vertebral Column –Spine
26 irregular bones connected by ligaments
Flexible, curved structure

74. Bones of the Axial Skeleton
Vertebral Column –Spine
Running through the central cavity of vertebral column is the delicate spinal cord
Spine preserves and protects spinal cord

75. Bones of the Axial Skeleton
Vertebral Column –Spine
Single vertebrae are separated by pads of flexible fibrocartilage called intervertebral discs
They cushion the vertebrae and absorb shock

76. Bones of the Axial Skeleton
Vertebral Column –Spine
Young Person
Discs have high water content ( 90%)
Discs are spongy and compressible

77. Bones of the Axial Skeleton
Vertebral Column –Spine
Aging
The water content of disc decreases
Drying of discs and weakening of ligaments predisposes older people to herniated discs (slipped disc)
if slipped disc presses on spinal cord- major pain

78. Bones of the Axial Skeleton
Vertebral Column –Spine
The spine has 2 curvatures
1. Primary Curvature
2. Secondary Curvature

79. Bones of the Axial Skeleton
Vertebral Column –Spine
Primary Curvature-
curvature in the thoracic and sacral regions
Called primary because it is there when we are born

80. Bones of the Axial Skeleton
Vertebral Column –Spine
Secondary Curvature-
Cervical curvature- develops when baby begins to lifts its head
Lumbar curvature- develops when baby begins to walk

81. Bones of the Axial Skeleton
Several types of abnormal spinal curvature
1. Scoliosis-

82. Bones of the Axial Skeleton
Several types of abnormal spinal curvature
2. lordosis-

83. Bones of the Axial Skeleton
Several types of abnormal spinal curvature
2. lordosis-

84. Several types of abnormal spinal curvature
3. kyphosis-

87. Bones of the vertebral column (backbone)

88. Bones of the Axial Skeleton
Bones of the Spinal Column (26 total)
1) Cervical Vertebrae (7 Bones)
Top seven vertebrae of the spinal column
The atlas (to bear )is the first cervical vertebrae
The axis is the second cervical vertebrae

89. Bones of the Axial Skeleton
Bones of the Spinal Column (26 total)
1) Cervical Vertebrae (7 Bones)

90. Bones of the Axial Skeleton
Bones of the Spinal Column (26 total)
2) Thoracic Vertebrae (12 Bones)
Middle 12 vertebrae of the spinal column

91. Bones of the Axial Skeleton
Bones of the Spinal Column (26 total)
3) Lumbar Vertebrae (5 Bones)
Bottom five vertebrae of the spinal column

92. Bones of the Axial Skeleton
Bones of the Spinal Column (26 total)
4) Sacrum (5 Bones Fused Into 1 Bone)
Five separate vertebrae that fuse into 1 bone after the bones mature

93. Bones of the Axial Skeleton
Bones of the Spinal Column (26 total)
5) Coccyx (4 or 5 Bones Fused Into 1 Bone)
Tailbone; consists of separate vertebrae that have fused together

95. Bones of the Axial Skeleton
Sternum and Ribs (25 total)
Sternum (1 Bone)
“Breastbone”

96. Bones of the Axial Skeleton
Ribs
You have two types of ribs
True Ribs
False Ribs

97. Bones of the Axial Skeleton
Sternum and Ribs (25 total)
Ribs (12 pairs = 24 Ribs)
True Ribs (First 7 pairs)
Ribs attach directly to the sternum by costal cartilage

98. Bones of the Axial Skeleton
Ribs
False Ribs (Bottom 5 pairs)
Rib pairs 8, 9, & 10 attach indirectly to the sternum by the costal cartilage of rib pair #7
Rib pairs 11 & 12 are called floating ribs because they do not attach to the sternum at all

99. Bones of the Axial Skeleton
All ribs attach to a thoracic vertebrae posteriorly

100. Bones of the Axial Skeleton
Bones of the Upper Extremities
The sternum, ribs, and vertebral column create the thorax

101. Bones of the Appendicular Skeleton
Bones of the Upper Extremities
Clavicle (2 Bones)
Collarbone

102. Bones of the Appendicular Skeleton
Bones of the Upper Extremities
Scapula (2 Bones)
Shoulder Blade

103. Bones of the Appendicular Skeleton
Bones of the Upper Extremities
The scapula and clavicle together make up the shoulder girdle

104. Bones of the Appendicular Skeleton
Bones of the Upper Extremities
Humerus (2 Bones)
Long bone of the upper arm

105. Bones of the Appendicular Skeleton
Bones of the Upper Extremities
Radius (2 Bones)
Ulna (2 Bones)
The radius and ulna are bones of the forearm
The radius is on the thumb side and the ulna is on the little finger side

106. Bones of the Appendicular Skeleton
Bones of the Upper Extremities
Carpals (16 Bones; 8 in Each Hand)
Bones of the wrist

107. Bones of the Appendicular Skeleton
Bones of the Upper Extremities
Metacarpals (10 Bones, 5 in Each Hand)
Bones in the palm of the hand

108. Bones of the Appendicular Skeleton
Bones of the Upper Extremities
Phalanges (28 Bones, 14 in Each Hand)
Bones of the fingers (3 in each finger and 2 in the thumb)

109. Bones of the Appendicular Skeleton
Bones of the Lower Extremities (Label bones in your notes !)

110. Skeletal Differences in Men & Women
Male Female
110

111. Skeletal Differences in Men & Women
111

112. Bones of the Appendicular Skeleton
Bones of the Lower Extremities
Femur Bone
Thigh bone
Longest, largest, and strongest bone in the body

113. Bones of the Appendicular Skeleton
Bones of the Lower Extremities
Patella (2 Bones)
Kneecap

114. Bones of the Appendicular Skeleton
Bones of the Lower Extremities
Tibia
Fibula
The tibia and fibula are the
bones of the lower leg
Tibia “shin bone” is larger,
medial, and more superficial
than the fibula

115. Bones of the Appendicular Skeleton
Bones of the Lower Extremities
Tarsal Bones (14 Bones, 7 in Each Foot)
Bones that form the heel and the posterior portion of the foot

116. Bones of the Appendicular Skeleton
Bones of the Lower Extremities
Metatarsals (10 Bones, 5 in each foot)
Bones that form the long portion of the foot

117. Bones of the Appendicular Skeleton
Bones of the Lower Extremities
Phalanges (28 Bones, 14 in each foot)
Bones of the toes (3 in each toe except big toe; big toe has 2 bones)