1. Chapter 11
Skeletal System

2. Points to Ponder What are the 5 functions of the skeletal system?
What are the parts of a long bone?
How do bones grow, remodel and repair?
How are hormones involved in bone growth?
What is osteoporosis?
How are age, gender and ethnicity determined through skeletal remains?
What are the components of the axial and appendicular skeletons?
What are synovial joints and what kind of angular movements to they allow?

3. Functions of the skeletal system
Supports the body
Legs: support the entire body while standing
Pelvic Girdle: supports the abdominal cavity
Protects the soft body parts
Skull: protects the brain
Rib cage: protects the lungs
Vertebrae: protects the spinal cord
Makes nervous connections to all the muscles of the limbs
Produces blood cells
Fetus: all the bones have red bone marrow
Adults: only certain bones produce blood cells
Stores minerals (calcium and phosphate) and fat
Bone matrix: contains calcium phosphate
Yellow marrow: fat storage
Allows for movement by attaching muscles
- Joints (articulations) occur between all bones

4. Anatomy of a long bone Diaphysis – shaft of the bone
made of compact bone and a large medullary cavity filled with yellow marrow
Epiphysis – ends of the bone
made mostly of spongy bone that contains red bone marrow
Articular cartilage
hyaline cartilage found on the ends of long bones where there is a joint
Yellow bone marrow
stores fat
Red bone marrow
makes blood cells found in spongy bone and flat bones

5. Anatomy of a long bone Periosteum Ligaments
living, outer covering of fibrous connective tissue.
Contains blood vessels, lymphatic vessels, and nerves.
Blood vessels penetrate the periosteum  enter the bone  branch within the central canals  feed into the canaliculi
Ligaments
fibrous connective tissue that connects bones
Periosteum is continuous with ligaments

6. Bone Compact bone Spongy bone
Composed of osteons with a central canal containing blood vessels
Contains living bone cells called osteocytes lie in chambers called lacunae
Matrix fills the space between the concentric circles of lacunae
Spongy bone
Made of plates, called trabaeculae, with spaces filled with red bone marrow
Lighter and designed for strength
Osteocytes are irregularly placed in trabeculae. Canaliculi bring osteocytes nutrients

8. Shape of Bones Long Bones: Short Bones: Flat Bones:
Longer than wide, consist of shaft and 2 ends
e.g. bones of appendages
Short Bones:
Approx. equal in all dimensions
e.g. carpals, tarsals
Flat Bones:
Thin, 2 parallel surfaces
e.g. skull, sternum, ribs, scapula
Figure 6–1a

9. Shape of Bones Irregular Bones: Sesamoid Bones: Sutural Bones:
Complex shapes
E.g. vertebrae, os coxa
Sesamoid Bones:
Seed shaped, form in tendon
E.g. patella, total number can vary
Sutural Bones:
- Extra bones in sutures of skull

10. Cartilage
Cartilage –
flexible connective tissue categorized based on the type and arrangement of matrix fibers
Contains many collagenous and elastic fibers
Cells = chondrocytes, lie within lacunae
No nerves and no blood vessels
Pads joints where stresses of movement are intense

11. Types of Cartilage Hyaline cartilage – Fibrocartilage –
firm and flexible, contains collagen fibers
ends of long bones, nose, ends of ribs, larynx and trachea
Fibrocartilage –
stronger, contains wide rows of thick collagen fibers
disks between vertebrae and in the knee; stronger than hyaline cartilage
Withstand tension and importance
Elastic cartilage –
more flexible, contains mostly elastic fibers
ear flaps and epiglottis; more flexible than hyaline cartilage

12. Cells in bone growth, remodeling and repair
Bones can grow throughout life to respond to stress by changing size, shape, and strength
Called bone remodeling and bone repair
Osteoblasts – bone-forming cells
Secrete organic matrix of bone
Promote the deposition of calcium salts into the matrix
Osteocytes – mature bone cells that maintain bone structure derived from osteoblasts
Derived from osteoblasts
Maintain structure of bones
Osteoclasts – bone-absorbing cells
Assist in depositing calcium and phosphate into blood
Chondroytes – cartilage-forming cells

13. 11.2 Bone growth, remodeling and repair
How does bone develop?
Ossification - the formation of bone in two distinct ways:
Intramembranous ossification –
- bone development between sheets of fibrous connective tissue; used in flat bones
Endochondrial ossification –
- cartilage is replaced by bone; used by most bones

14. Intramembranous Ossification
Bone develops from fibrous CT in dermis
Also called dermal ossification:
because it occurs in the dermis
produces dermal bones such as mandible and clavicle
Produces skull bones
There are 4 main steps in intramembranous ossification

15. Intramembranous Ossification: Step 1
Ossification center appears in the fibrous CT membrane
Mesenchymal cells aggregate
Differentiate into osteoblasts
Begin ossification at the ossification center

16. Intramembranous Ossification: Step 2
Bone matrix (osteoid) is secreted within the fibrous membrane
Osteoblasts begin to secrete osteoid, which is mineralized
Trapped osteoblasts become osteocytes

17. Intramembranous Ossification: Step 3
Woven bone and periosteum form
Accumulating osteoid is laid down between blood vessels, which form a random network
Vascularized mesenchyme condenses on the external face of the woven bone and becomes periosteum around spongy bone

18. Intramembranous Ossification: Step 4
Bone collar of compact bone forms and red marrow appears
Trabeculae deep to the periosteum thickens, forming a woven bone collar that is later replaced with mature bone
Spongy bone, consisting of distinct trabeculae, persists internally and its vascular tissue becomes red marrow

19. Endochondral Ossification
Growth and ossification of long bones occurs in 6 steps

20. How does endochondral ossification occur?
11.2 Bone growth, remodeling and repair
How does endochondral ossification occur?
1st Cartilage model – chondrocytes lay down hyaline cartilage in the shape of the future bones
- Cartilage models calcify, chondrocytes die off
2nd Bone collar formation – osteoblasts secrete bone matrix and results in a collar made of compact bone
3rd Primary ossification center – osteoblasts are brought interiorly by blood and lay down spongy bone
4th Secondary ossification sites – bone centers in the epiphyses formed after birth
5th Epiphyseal plate – a cartilage band that acts as a growth plate that allows bones to lengthen

21. Endochondral Ossification: Step 2
Blood vessels grow around the edges of the cartilage
Cells in the perichondrium change to osteoblasts:
Secrete osteoid
Osteiod is mineralized and produces a layer of superficial bone around the shaft which will continue to grow around the diaphysis and become compact bone
Figure 6–9 (Step 2)

22. Endochondral Ossification: Step 3
Capillaries and osteoblasts migrate into the primary ossification center:
Blood vessels enter the cartilage
Bringing osteoblasts that secrete osteoid
Mineralized into trabeculae
Spongy bone develops at the primary ossification center and continues to growth toward the epiphysis
Figure 6–9 (Step 3)

23. Endochondral Ossification: Step 3
Remodeling creates a marrow cavity:
Osteoclasts degrade trabeculae in the center to create the marrow cavity
Bone increases in length to epiphyseal plate followed by replacement of plate cartilage by spongy bone
Cartilage continues to grow on epiphyseal side and is replaced by bone on diaphysis side
Bone increases in diameter
Figure 6–9 (Step 4)

24. Endochondral Ossification: Step 4
Secondary ossification centers form in epiphyses:
Capillaries and osteoblasts enter the epiphyses:
creating secondary ossification centers
Figure 6–9 (Step 5)

25. Endochondral Ossification: Step 5
Epiphyses become ossified with spongy bone
Hyaline cartilage remains on articular surfaces (not calcified or ossified)
Ossification continues at both 1°and 2° ossification centers until all epiphyseal cartilage has been replaced with bone  epiphyseal closure
Adult bone retains the epiphyseal line
Figure 6–9 (Step 6)

26. Visualizing endochondral ossification

27. 11.2 Bone growth, remodeling and repair
How do bones lengthen?

28. How do hormones affect bone growth?
11.2 Bone growth, remodeling and repair
How do hormones affect bone growth?
Growth hormone (GH) – stimulates general bone growth and the epiphyseal plates
Thyroid hormone
Promotes metabolic activity of cells
Too much = gigantism
Too little = dwarfism
Sex hormones – increases growth during adolescence
Stimulate osteoblast activity at the epiphyseal plate
Vitamin D – converted to a hormone to allow calcium absorption in the intestine
Too little = rickets, bone deformities and bowed long bones

29. Bone remodeling and role in homeostasis
Bone remodeling – bone renewal at a rate of up to 18% per year
Remodeling allows bones to respond to stress
Homeostasis Regulations is Necessary
Too much calcium = neurons and muscle cells no longer function
Too low calcium = neurons and muscle cells become excited, convulsions occur

30. Bones role in homeostasis
Regulates the calcium in the blood through hormones:
Parathyroid hormone (PTH) – increases blood calcium by accelerating bone recycling
Increased activity of osteoclasts
Calcitonin – decreases blood calcium by increasing calcium bone absorption
Increased activity of osteoblasts

31. Health focus: Osteoporosis
11.2 Bone growth, remodeling and repair
Health focus: Osteoporosis
Osteoporosis – bones are weakened due to a decreased bone mass
Bone reabsorption exceeds absorption usually by age 40
Risk factors: women, white or Asian, thin, family history, early menopause, smoking, diet low in calcium, excessive caffeine or alcohol consumption and a sedentary lifestyle
Can lead to fractures and other complications
Can be treated with drugs, hormones and lifestyle change

32. (b) Spongy bone in osteoporosis
(a) Normal spongy bone
SEM X 25
(b) Spongy bone in osteoporosis
SEM X 21

33. Bone Remodeling Bones respond to stress of activity
Activity causes use of particular bone
Enlarge in diameter
1. Osteoblasts in periosteum form compact bone around the external bone surface
2. Osteoclasts break down bone in internal bone surface, around medullary cavity
Prevents bones from getting too heavy and thick
Exercise
stimulates osteoblasts instead of osteoclasts

34. 11.2 Bone growth, remodeling and repair
Steps in bone repair
1.Hematoma (6-8 hrs.) – blood clot formed between broken bones where blood escapes from the ruptured blood vessels
2. Fibrocartilaginous callus (~ 3 weeks) – cartilaginous callus forms between broken bones
3. Bony callus (3-4 months) – cartilaginous callus is turned to bone
Joins the broken bones together
4. Remodeling – old bone tissue is replaced by new bone tissue
Osteoblasts build new compact bone
Osteoclasts absorb spongy bone creating medullary cavity

35. 11.2 Bone growth, remodeling and repair
Bone repair

36. The 206 bones of the skeleton

37. Science focus: Skeletal remains
11.3 Bones of the axial skeleton
Science focus: Skeletal remains
Characteristics to be determined:
Age: approximated through dentition, studying areas of bone ossification and joint condition
Gender: pelvic bone is best used, thickness of long bones, skull characteristics
Female = pelvis is shallow and wider
Male = Long bones, humerus and femur are thicker and denser
Ethnicity: difficult to tell but skull characteristics are most useful

38. Comparing the Male and Female Pelvis
Smoother and lighter
less prominent muscle and ligament attachments
Enlarged pelvic outlet
Broad pubic angle (> 100°)
Wide and Broad

39. The Axial Skeleton
Figure 7–1a

40. Axial Skeleton

41. The axial skeleton Skull – made of cranium and facial bones Hyoid bone
11.3 Bones of the axial skeleton
The axial skeleton
Skull – made of cranium and facial bones
Hyoid bone
Does not articulate (join) with another bone, attached to the
temporal bones by muscles and ligaments
larynx by a membrane
Function:
Anchors the tongue
Serves as the site for the attachment of muscles associated with swallowing
Vertebral column – vertebrae and intervertebral disks
Rib cage – ribs and sternum

42. The skull – the cranium Cranium Protects the brain Composed of 8 bones
Frontal bone (1): forehead
Parietal bones (2): extend to the sides
Occipital bone (1): curves to form the base of the skull
Foramen magnum, spinal cord passes and becomes the brain stem
Temporal bones (2): has a opening (external auditory canal) leads to middle ear
Sphenoid bones (2): extends across the floor of the cranium
Keystone bone because all bones articulate with it

44. The skull – the cranium
Newborns, cranial bones are not completely formed but joined by membranous regions called fontanels
16 months they close via imtramembranous ossification
Some contain sinuses
Air spaces line by mucous membrane
Functions:
Reduce weight of the skull
Give a resonant sound to the voice

45. Facial Bones
Mandible, maxillae, zygomatic bones, and nasal bones are most prominent
1. Mandible: Lower jaw
Only movable portion of the skull
Permits us to chew our food
2. Maxillae: Upper jaw and the anterior portion of the hard palate
3. Zygomatic Bone: Cheekbone
4. Nasal Bone: form the bridge of the nose
Ethmoid and vomer: part of the nasal septum
Lacrimal bone: contain opening for the nasolacrimal canal (drains tears)

46. Bones of the face and the hyoid bone
11.3 Bones of the axial skeleton
Bones of the face and the hyoid bone

47. Vertebral column Types of vertebrae 33 vertebrae Cervical (7)
Thoracic (12)
Lumbar (5)
Sacrum (5 fused)
Coccyx (4 fused into tailbone)
Intervertebral disks
Fibrocartilage between vertebrae

48. Cervical Vertebrae Atlas: First cervical vertebrae
Holds up the head
Movement of head to indicate “yes” and hilting the head from side to side
Axis: second cervical vertebra
Allows a degree of rotation
Movement of head to indicate “no”

49. The Vertebrae
Figure 7–20a

50. Comparing Vertebrae

51. Characteristics of the Sacrum and Coccyx
is curved, more in males than in females
protects reproductive, urinary, and digestive organs
The coccyx:
attaches ligaments and a constricting muscle of the anus

52. Primary Curves Thoracic and sacral curves:
are called primary curves (present during fetal development)
or accommodation curves (accommodate internal organs)

53. Secondary Curves Lumbar and cervical curves:
are called secondary curves (appear after birth in first year of life)
or compensation curves (shift body weight for upright posture)
Necessary for bipedalism
Cervical: holds head up
Lumbar: standing

54. Abnormalities in Curvature
Kyphosis:
- exaggerated thoracic curvature
Lordosis:
- exaggerated lumber curvature
Scoliosis:
- abnormal lateral curvature

55. Construction of Column
Elastic ligaments:
link bodies for alignment
Intervertebral foramen:
holes formed by spacing from discs, allow spinal nerves to exit column
Vertebral Foramen:
Hole for spinal cord
Vertebral Canal:
Bony canal for spinal cord
Formed by stacking of vertebral foramen

56. The Vertebral Canal
Figure 7–17d,e

57. Functions of the Thoracic Cage
Protects organs of the thoracic cavity:
heart, lungs, and thymus
Attaches muscles:
for respiration
of the vertebral column
of the pectoral girdle
of the upper limbs

58. The rib cage Ribs – protects heart and lungs Sternum = breastbone
11.3 Bones of the axial skeleton
The rib cage
Ribs – protects heart and lungs
Flattened bone originating from the thoracic vertebrae
Sternum = breastbone
Manubrium articulates with the clavicles and the first pair of ribs
Xiphoid process serves as an attachment site for the diaphragm

59. The Rib Cage
Formed of ribs and sternum
Figure 7–22a

60. Ribs Ribs (costae): Ribs are divided into 3 types:
are 12 pairs of long, curved, flat bones
extending from the thoracic vertebrae
Ribs are divided into 3 types:
1. 7 pairs of true ribs:
Separate cartilage to attach to sternum
2. 3 pairs of false ribs:
Common shared cartilage to attach to sternum
3. 2 pairs of floating ribs:
- no cartilage, no attachment to sternum

61. Articulations of Ribs and Vertebrae
Figure 7–22b

62. The Ribs
Figure 7–23

63. Functions of Ribs Ribs: Rib movements (breathing): are flexible
are mobile
can absorb shock
Rib movements (breathing):
affect width and depth of thoracic cage
changing its volume

64. Appendicular Skeleton
126 bones
Consists of limbs and limb girdles to provide movement
Pectoral girdle: 4 bones
Upper limbs: 60 bones
Pelvic girdle: 2 bones
Lower limbs: 60 bones

66. The appendicular skeleton
11.4 Bones of the appendicular skeleton
The appendicular skeleton
Pectoral girdle and upper limb
Pelvic girdle and lower limb

67. Appendicular skeleton
Pectoral girdle
Scapula and clavicle
Upper limb
Arm and hand bones

68. The Pectoral Girdle
Figure 8–2a

69. The Pectoral Girdle Also called the shoulder girdle
Connects the arms to the body
Positions the shoulders
Provides a base for arm movement
Consists of:
2 clavicles
2 scapulae
Connects with the axial skeleton only at the manubrium

70. The Clavicles Also called collarbones Long, S-shaped bones
Originate at the manubrium (sternal end)
Articulate with the scapulae (acromial end)

71. The Clavicles
Figure 8–2b, c

72. The Scapula Broad, flat triangles Articulate with arm and collarbone
Muscles of the arm and chest attach to the coracoid process of the scapula
Glenoid cavity of the scapula articulates with the head of the humerus
Rotator cuff
Tendons that extend to the humerus from the muscles originating on the scapula
Increased movement = decreased stability
Function to rotate the head of the humerus medially (internal rotation)
Function to draw the humerus forward and downward when the arm is raised

73. Structures of the Scapula
Figure 8–3c

74. The Humerus Also called the arm The long, upper armbone
Deltoid tuberosity
- deltoid, shoulder
muscle, attaches
Capitulum and trochlea
- articulate with the
radius and ulna at the
elbow

75. The Forearm Also called the antebrachium Consists of 2 long bones:
ulna (medial)
radius (lateral)
Radial Tuberosity
Insertion of bicep brachii
Ulnar Tuberosity
Insertion of brachialis
Styloid Process
Muscle attachment for ulna or radius
Figure 8–5

76. The Wrist
Figure 8–6

77. Appendicular skeleton
Pelvic girdle
coxal bone
Ilium
Ischium
Pubis
Bears the weight of the body, protects the organs in pelvic cavity, serves as the place of attachment for the legs
Lower limb
Leg and foot bones

78. The Pelvis
Figure 8–8

79. The Pelvis Consists of 2 ossa coxae, the sacrum, and the coccyx
Stabilized by ligaments of pelvic girdle, sacrum, and lumbar vertebrae
Obturator Foramen
Opening for nerves and muscles to pass through
Acetabulum: where all the bones of coxal join
Head of the femur meets with the pelvis; hip-joint
Ischium has Ischial spine: muscle attachment
Ischial Tuberosity
Point of insertion for the semimembranosus, head of biceps femoris, and semitendinosus

80. Bones of the Lower Limbs
Femur (thigh)
Patella (kneecap)
Tibia and fibula (leg)
Tarsals (ankle)
Metatarsals (foot)
Phalanges (toes)

81. The Femur
The longest, heaviest bone
Figure 8–11

82. Femur Articulates with the coxal bones at the acetabulum Trochanters
Greater and lesser trochanters
Attachment for thigh muscles, buttock muscles, hip flexors, and tendon attachments
Shaft:
attaches hip muscles
Distal End: medial and lateral condyles
Articulate with the tibia of the leg
Attachments for ligaments of the knee joint

83. The Patella: Kneecap Held in place by the quadriceps tendon,
continues as ligament that attaches to the
tibial tuberosity
Figure 8–12

84. The Tibia
Figure 8–13

85. The Tibia Also called the shinbone Supports body weight
Larger than fibula
Medial to fibula
Tibial Tuberosity
Attachment for the
ligamentum patellae

86. The Fibula Attaches muscles of Smaller than tibia Lateral to tibia
feet and toes
Smaller than tibia
Lateral to tibia

87. The Ankle Also called the tarsus: consists of 7 tarsal bones Talus:
carries weight from tibia across trochlea
Calcaneus (heel bone):
transfers weight from talus to ground
attaches Achilles tendon
Figure 8–14a

88. Feet: Arches Arches transfer weight from 1 part of the foot to another
Figure 8–14b

89. Types of joints (where bones meet bones)
11.5 Articulations
Types of joints (where bones meet bones)
Fibrous – usually immovable
sutures between cranial bones
Cartilaginous – tend to be slightly movable
intervertebral disks
Synovial – freely movable joints
ball-and-socket hip and shoulder joints and the knee joint

90. Synovial Joint Synovial Fluid  Lubricant for the joint
Fill the cavity
Ligaments  Support or strength a joint
Connect bone to bone
Bursae  Ease friction between bone and muscle
Fluid-filled sacs
Meniscus  Adds stability, acts as shock absorbers
C-shaped pieces of hyaline cartilage between the bones
Types of Synovial Joints
1. Ball and socket joint
Hips and shoulder, movement in all planes
2. Hinge joints
Elbow and knee joint
Permit movement in one direction only

91. Anatomy of a synovial joint

92. Summary of synovial joints movements
11.5 Articulations
Summary of synovial joints movements
Flexion –
decrease in joint angle
Extension -
increase in joint angle
Adduction –
body part moves toward midline
Abduction –
body part moves away from midline
Inversion –
sole of foot turns inward
Eversion –
sole of foot turns outward

93. Visualizing synovial joints movements
11.5 Articulations
Visualizing synovial joints movements