1. Chapter 6: Introduction to the Skeletal System
Copyright 2010, John Wiley & Sons, Inc.

2. Chapter 6: Introduction to the Skeletal System
The skeletal system provides a framework for all of the other structures in the body
The skeletal system consists of bones, cartilages, ligaments, and tendons
Each bone is a dynamic structure that contains multiple tissues
Long term changes in bone at the tissue level can lead to an overall change in bone shape and strength
Copyright 2010, John Wiley & Sons, Inc.

3. The Skeletal System Performs Six Key Functions in the Body
Support - the structural framework of the body
Protection - bones protect sensitive internal organs
Movement - bones and joints allow muscular actions
Mineral homeostasis - bones store calcium and other important minerals
Blood cell production - all blood cells originate in the red bone marrow
Triglyceride storage
Copyright 2010, John Wiley & Sons, Inc.

4. The Six Key Functions of the Skeletal System Fall into Two Groups
STRUCTURAL ROLES
Support
Protection
Movement
HOMEOSTASIS
Mineral homeostasis
Blood cell production
Triglyceride storage
Copyright 2010, John Wiley & Sons, Inc.

5. Bones are Classified into One of Five Basic Shapes
Copyright 2010, John Wiley & Sons, Inc.

6. Classification of Bone
Long
Flat
Short
Irregular
Sesamoid

7. Long bones - slightly curved for strength
femur, tibia, fibula, humerus, ulna, radius, phalanges
Short bones - cube shaped
carpals and tarsals
Flat bones - thin, protection, muscle attachment.
cranial bones, sternum, ribs, scapula

8. Irregular bones - complex shape
vertebrae, hip bones, facial bones,
heel bone (calcaneus)
Sesamoid bones – seed shaped
develop in tendons due to friction
palms of hands, soles of feet, patella

9. Long Bones - Anatomy and Terminology
Regions of a long bone
1 diaphysis [the shaft]
2 metaphyses
2 epiphyses (proximal and distal)
1 marrow cavity
Surface tissues
Endosteum
Periosteum
Articular cartilage
Copyright 2010, John Wiley & Sons, Inc.

10. Anatomy of a long bone Diaphysis=shaft Epiphysis=ends
Metaphysis=between diaphysis and epiphysis
Articular cartilage=hyaline cartilage
covering the epiphysis
Periosteum=layer of CT covering outside of bone
Medullary cavity=marrow cavity
contains yellow bone marrow
Endosteum= layer of CT that
lines medullary cavity

11. Anatomy of a long bone

12. Long Bones - Anatomy and Terminology
Copyright 2010, John Wiley & Sons, Inc.

13. Histology of bone What type of tissue is bone?
Extracellular matrix= 25% water, 25% collagen fibers, 50% crystalllized mineral salts(hydroxyapatite)
Hardness of bone is due to mineral salts
Tensile strength (resistance to being stretched or torn apart) due to collagen fibers

14. Bone Strength

15. CONCEPT CHECK DEC 3 You know what to do…
1. These bones are characterized by a cube-like shape and include the carpals.
2. Where is red bone marrow found within a long bone?
3. Bone is classified as this tissue type.
4. New growth occurs in this region of a long bone.
5. Which three functions of bone have structural roles in the human body?

16. CONCEPT CHECK DEC 3 You know what to do… 1. SHORT BONES
2. IN THE EPIPHYSES
3. CONNECTIVE TISSUE
4. METAPHYSES ALONG THE EPIPHYSEAL LINES
Growth Plates
5. STRUCTURE, PROTECTION, MOVEMENT

17. A&P Critical Thinking Extension
Humans are the most advanced species on Earth.
All living things are said to progressively evolve to best survive and reproduce in their environments.
Is it possible that humans have degenerated in some way? (Consider Anatomy and Physiology of the Human Body)

18. Bone Mass and Growth
“Modern human skeletons have shifted quite recently towards lighter—more fragile, if you like—bodies. It started when we adopted agriculture. Our diets changed. Our levels of activity changed,” says study co-author Habiba Chirchir, an anthropologist in the Smithsonian’s Human Origins Program.
“Modern humans had 50 to 75 percent less dense trabecular bone than chimpanzees”
Thickness, volume, and surface area of cancellous bone is very indicative of bone joint strength.
Read more:

20. Cells of Bone Osteogenic cells=unspecialized stem cells.
Undergo cell division.
Develops into osteoblast
Osteoblast= cells that form bone do
not undergo mitosis. Secrete
collagen to build bone

21. Cells of Bone Osteocytes= mature bone cells derived from osteoblasts .
No mitosis. Involved in exchange
of nutrients and wastes in the blood.
Osteoclasts=derived from
monocytes(wbc)
function in bone resorption
(breakdown of matrix)

22. Osseous Tissue - Four Cell Types
Copyright 2010, John Wiley & Sons, Inc.

23. CONCEPT CHECK DEC 7
1. These cells are unspecialized and develop into osteoblasts.
2. This bone cell does not divide and assists in the exchange of nutrients and waste.
3. What is the function of an osteoclast?
4. Osteoblasts secrete this substance to build strong bones.

24. CONCEPT CHECK ANSWERS DEC 7
3 POINTS EACH = 12 TOTAL POINTS
1. OSTEOGENIC CELLS
2. OSTEOCYTE
3. BONE RESORPTION
Break down of matrix
4. COLLAGEN

25. Osseous Tissue - Four Cell Types
Copyright 2010, John Wiley & Sons, Inc.

26. Bones Contain Two Types of Osseous Tissues
Compact bone is more dense
Provides strength of long bones.
Spongy bone is the predominant tissue in flat bones
Strength due to trabeculae
Copyright 2010, John Wiley & Sons, Inc.

27. Types of Osseous Tissue
Compact - Forms the external layer of all bone
Protects against the stress of weight and movement.
Highly organized
concentric ring structure
allows nutrients and O2 to reach spaces.

28. Types of Osseous Tissue
-osteon=repeating structural unit in compact bone - central canal(Haversial system)=open space containing blood vessels - concentric lamellae= rings in calcified matrix - canaliculi(little canals)=nutrients diffuse through these canals -interstitial lamellae=fill spaces between concentric lamellae

29. Spongy bone- 20% of skeleton.
-Does not contain osteons.
-more spaces, less strength.
-lamellae arranged in an irregular lattice work
of thin plates of bone called trabeculae.
-Spaces between trabeculae filled with red marrow

30. Spongy bone- 20% of skeleton.
-Found in short, flat and irregular bones
epiphyses of long bones.
-Blood cells are formed in red marrow of spongy bone
-hipbones, ribs, sternum, vertebrae, skill epiphyses of some long bones

31. Bones Have an Extensive Blood Supply
Osseous tissues have a rich blood supply, important in bone development and homeostatic regulation
Bones also contain many sensory neurons, resulting in considerable pain when bones are injured
Copyright 2010, John Wiley & Sons, Inc.

32. This could be your project idea!

33. Bone Tissue Interactions Animation
Bone Dynamics and Tissue
You must be connected to the internet to run this animation.
Copyright 2010, John Wiley & Sons, Inc.

34. CONCEPT CHECK DEC 10 1. What is the function of cortical bone?
2. Describe the structure of spongy bone.
3. Why do bones require blood vessels?
4. Which classifications of bone are primarily comprised of spongy bone?

35. CONCEPT CHECK DEC 10 4 Points EACH 16 TOTAL POINTS
1. What is the function of cortical bone?
Protects against weight and movement
2. Describe the structure of spongy bone.
Irregular lattice work of trabeculae
3. Why do bones require blood vessels?
Living cells require oxygen for cellular functions
4. Which classifications of bone are primarily comprised of spongy bone?
Short, Flat, Irregular

36. Compact Bone - Osteons as Structural Subunits
Copyright 2010, John Wiley & Sons, Inc.

37. Spongy Bone - Trabeculae Appear Random But Are Not
Copyright 2010, John Wiley & Sons, Inc.

38. Bone Formation Ossification is process by which bones form.
Three instances
1. The initial formation of bones in the embryo and fetus
2. The growth of bones until their adult sizes are reached
3. The remodeling and repair of bones

39. Two types of bone formation
1. Intramembranous= flat bones of skull and mandible formed in this way
2. Endochondral= the replacement of cartilage by bone

40. Bones Form by Two Very Different Mechanisms
Intramembranous ossification
Tissue develops directly within sheet-like layers
Making of some flat bones (notably in the skull and mandible)
Endochondral ossification
Formation of bone cells inside a pre-existing hyaline cartilage model
Responsible for most of our bones (including all long bones)
Copyright 2010, John Wiley & Sons, Inc.

41. 1
Blood capillary
Ossification center
Mesenchymal cell
Osteoblast
Mesenchyme
condenses
Blood vessel
Spongy bone
trabeculae
Periosteum
Spongy bone tissue
Compact bone tissue
Development of ossification center
Calcification
Formation of trabeculae
Development of the periosteum
Mandible
Flat bone
of skull 3 4 2
Collagen fiber
Osteocyte in lacuna
Canaliculus
Newly calcified bone
matrix 1
Blood capillary
Ossification center
Mesenchymal cell
Osteoblast
Development of ossification center
Calcification
Mandible
Flat bone
of skull 2
Collagen fiber
Osteocyte in lacuna
Canaliculus
Newly calcified bone
matrix
Mesenchyme
condenses
Blood vessel
Spongy bone
trabeculae
Formation of trabeculae 3 1
Blood capillary
Ossification center
Mesenchymal cell
Osteoblast
Osteocyte in lacuna
Canaliculus
Newly calcified bone
matrix
Development of ossification center
Calcification
Mandible
Flat bone
of skull 2
Collagen fiber 1
Blood capillary
Ossification center
Mesenchymal cell
Osteoblast
Collagen fiber
Development of ossification center
Mandible
Flat bone
of skull

42. Endochondral Ossification
Step 1 -The cartilage model forms
Step 2 – Model grows with growth of the body
Step 3 - Primary ossification center forms when the artery provides blood.
Medullary cavity forms.
Step 4 - Blood vessel entry into epiphyses stimulates development of
secondary ossification centers.
Step 5 - Residual hyaline cartilage remains on the surface of epiphyses
and at epiphyseal plate
Copyright 2010, John Wiley & Sons, Inc.

43. Copyright 2010, John Wiley & Sons, Inc.
Growth of Long Bones
Epiphyseal plate is the site of long bone growth
Zones of hyaline cartilage involved
Replacement of cartilage with bone
At 18–21 years old, the epiphyseal plate stops growing and is replaced by osseous tissue
Area becomes fused indicating an end to growth
Different bones fuse at different ages
Age varies by gender and other factors
Copyright 2010, John Wiley & Sons, Inc.

44. 1
Development of
cartilage model
primary ossification
center
the medullary
cavity
Growth of 2 3 4
Hyaline
cartilage
Calcified
matrix
Periosteum
(covering
compact bone)
Uncalcified
Medullary
Nutrient
artery and vein
artery
Perichondrium
Proximal
epiphysis
Distal
Diaphysis
Primary
ossification
Secondary
Epiphyseal
artery and
vein
Development of secondary
ossification center 5
Spongy
bone 1
Articular cartilage
Spongy bone
Epiphyseal plate
Secondary
ossification
center
Nutrient
artery and vein
Uncalcified
matrix
Epiphyseal
artery and
vein
Formation of articular cartilage
and epiphyseal plate
Development of secondary
ossification center
Development of
cartilage model
primary ossification
the medullary
cavity
Growth of 2 3 4 5 6
Hyaline
cartilage
Calcified
Periosteum
(covering
compact bone)
Medullary
artery
Perichondrium
Proximal
epiphysis
Distal
Diaphysis
Primary
Spongy
bone 1
Hyaline
cartilage
Calcified
matrix
Periosteum
(covering
compact bone)
Uncalcified
Medullary
cavity
Nutrient
artery and vein
artery
Perichondrium
Proximal
epiphysis
Distal
Diaphysis
Development of
cartilage model
primary ossification
center
the medullary
Growth of
Primary
ossification 2 3 4
Spongy
bone 1
Development of
cartilage model
primary ossification
center
Growth of 2 3
Hyaline
cartilage
Uncalcified
matrix
Calcified
Nutrient
artery
Perichondrium
Proximal
epiphysis
Distal
Diaphysis
Periosteum
Primary
ossification
Spongy
bone 1
Development of
cartilage model
Growth of 2
Hyaline
cartilage
Uncalcified
matrix
Calcified
Perichondrium
Proximal
epiphysis
Distal
Diaphysis 1
Development of
cartilage model
Hyaline
cartilage
Perichondrium
Proximal
epiphysis
Distal
Diaphysis

45. Bone Formation Interactions Animation
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Copyright 2010, John Wiley & Sons, Inc.

46. Copyright 2010, John Wiley & Sons, Inc.
Growth of Long Bones
Copyright 2010, John Wiley & Sons, Inc.

47. Copyright 2010, John Wiley & Sons, Inc.
Growth of Long Bones
Copyright 2010, John Wiley & Sons, Inc.

48. Bone Growth Interactions Animation
Bone Elongation and Bone Widening
You must be connected to the internet to run this animation.
Copyright 2010, John Wiley & Sons, Inc.

49. Factors Affecting Bone Growth
Growth and maintenance of bones depends on:
Adequate nutrition (energy, calcium, many vitamins)
Hormones
Growth Hormone and IGF’s stimulate bone growth
Thyroid hormone and insulin also promote bone growth
Sex steroids (estrogen and testosterone) stimulate bone growth in gender specific patterns
Epiphyseal plate closure results from higher levels of estrogens
Copyright 2010, John Wiley & Sons, Inc.

50. Bone Remodeling Interactions Animation
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Copyright 2010, John Wiley & Sons, Inc.

51. Fractures
Classified according to the position of the bone end after it breaks

52. Compound
Bone ends penetrate the skin

53. Simple
Bone ends do not penetrate the skin

54. Comminuted
Bone fragments into 3 or more pieces. Common in elderly due to brittle bones

55. Greenstick
Bone breaks incompletely, one side bent, one side broken. Common in children whose bone contains more collagen and are less mineralized

56. Spiral
Ragged break caused by excessive twisting forces. Sports injury

57. Impacted
One bone fragment is driven into the other

58. Bone Growth Growth in length involves 2 major events
-Replacement of cartilage on the epiphyseal plate(layer of hyaline cartilage in the metaphysis of growing bone) with osseous tissue
-Replacement of cartilage on the diaphyseal side of the epiphyseal plate with osseous tissue.

59. Factors affecting growth
Minerals
Calcium, phosphorus, magnesium, boron manganese
Vitamins
D, A, B12, C
Hormones
-Human growth hormone(HGH) great effect on height
-Sex hormones(estrogen/testosterone) promote activity in epiphyseal plate during puberty