1. Chapter 6 *Lecture Outline
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2. Chapter 6 Outline Cartilage Bone Classification and Anatomy of Bones
Ossification
Homeostasis and Bone Growth
Bone Markings
Aging of the Skeletal System

3. Intro to the Skeletal System
An organ system with tissues that grow and change throughout life
bones
cartilages
ligaments
other supportive connective tissues

4. Cartilage Semi-rigid connective tissue
not as strong as bone, more flexible/resilient
mature cartilage is avascular
Cells
chondroblasts: produce matrix
chondrocytes: surrounded by matrix
live in small spaces called lacunae

5. Distribution of Cartilage
Figure 6.1

6. Functions of Cartilage
Support soft tissues
airways in respiratory system
auricle of ear
Articulations
smooth surfaces where bones meet
Precursor model for bone growth
fetal long bones

7. Growth of Cartilage Two patterns Interstitial growth
from inside of the cartilage
Appositional growth
along outside edge of the cartilage

8. Interstitial Growth Mitosis of chondrocytes in lacunae
forms two chondrocytes per lacuna
each synthesize and secrete new matrix
new matrix separates the cells
Result:
larger piece of cartilage
newest cartilage inside

9. Figure 6.2

10. Appositional Growth Mitosis of stem cells in perichondrium Results:
adds chondroblasts to periphery
produce matrix, become chondrocytes
forming new lacunae
adding to existing matrix
Results:
larger piece of cartilage
newest cartilage on outside edges

11. Figure 6.2

12. Bones Living organs containing all four tissue types
primarily connective tissue
extracellular matrix is sturdy and rigid
strengthened by calcification: minerals deposited in the matrix (main store and source of Ca++ and PO4---)

13. Function of Bones
Support
Protection
Movement
Hemopoiesis
Storage

14. Classifying Bones Long bones Short bones Flat bones Irregular bones
greater length than width
Short bones
nearly equal length and width
Flat bones
thin surfaces
Irregular bones
other/complex shapes

15. Classification of Bones According to Shape
Figure 6.3

16. Long Bone Anatomy Diaphysis Epiphyses Metaphyses
elongated, usually cylindrical, shaft
Epiphyses
knobby, enlarged regions at ends
strengthen joints
attachment site for tendons/ligaments
Metaphyses
between diaphysis and epiphysis
contains epiphysial (growth) plate

17. Long Bone Anatomy
Figure 6.4

18. Long Bone Anatomy Articular cartilage Medullary/marrow cavity
thin layer of hyaline cartilage on epiphyses
reduces friction between articulating bones
Medullary/marrow cavity
cylindrical space in diaphysis
usually contains yellow bone marrow

19. Long Bone Anatomy Figure 6.4
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
(c)
Proximal
epiphysis
Metaphysis
Diaphysis
Distal
Articular cartilage
Epiphyseal line
Spongy bone
(contains red
bone marrow)
Compact bone
Medullary cavity
(contains yellow bone
marrow in adult)
Endosteum
Periosteum
Nutrient artery
through nutrient foramen
Perforating fibers
Figure 6.4

20. Bone Coverings Periosteum Endosteum dense irregular connective tissue
covers external surfaces of bones
does not cover articular cartilages
acts as anchor for blood vessels and nerves
anchored by perforating fibers embedded in the bone matrix
Endosteum
covers most internal surfaces of bones

21. Bone Coverings
Figure 6.5

22. Bone Cells
Osteoprogenitors: mesenchymal stem cells, found in endosteum and periosteum, mitotically produce more stem cells or osteoblasts
Osteoblasts: form bone matrix
Osteocytes: reside in lacunae; maintain matrix and communicate with osteoblasts to cause further deposit of bone matrix
Osteoclasts: large, multinucleate cells that dissolve bone, releasing Ca++

23. Bone Cells
Figure 6.6

24. Bone Matrix 1/3 organic components cells collagen fibers
ground substance
2/3 inorganic components
bone salt crystals: hydroxyapatite
calcium phosphate and hydroxide
Ca10(PO4)6(OH)2

25. Comparing Bone Tissues
Compact bone
solid and relatively dense
external surfaces of long and flat bones
Spongy bone
open lattice of narrow plates: trabeculae
internal surface of bones

26. Flat Bones
Have compact and spongy (diploë) bone
Figure 6.7

27. Compact Bone Organization
The basic structural and functional unit of mature compact bone is the osteon
also known as a Haversian system
cylindrical structures
parallel to the shaft of the bone

28. Osteon Components Canals Lamellae
central: carries blood vessels and nerves
perforating: perpendicular connections to central canal with blood vessels and nerves
canaliculi: between lacunae allowing metabolic interactions between osteocytes
Lamellae
concentric: rings of bone around central canal
circumferential: along endosteum and periosteum
interstitial: “leftover” pieces of old osteons

29. Osteon or Haversion System
Figure 6.8

30. Ossification The formation and development of bone
also known as osteogenesis
begins by 8th week of embryonic development and continues into adulthood
Two general patterns:
Intramembranous
Endochondral

31. Patterns of Ossification
Intramembranous ossification
develops from mesenchyme
produces flat bones of the skull, some facial bones, the mandible, and central portion of clavicle
Endochondral ossification
begins with a hyaline cartilage model
produces the majority of bones in the body

32. Stages of Intramembranous Ossification
Ossification centers form within thickened regions of mesenchyme
Figure 6.10

33. Stages of Intramembranous Ossification
Osteoid (precursor to solid bone matrix) undergoes calcification
Figure 6.10

34. Stages of Intramembranous Ossification
Woven (primary) bone and surrounding periosteum form
Figure 6.10

35. Stages of Intramembranous Ossification
Lamellar (secondary) bone replaces woven bone as compact and spongy bone form
Figure 6.10

36. Stages of Endochondral Ossification
Fetal hyaline cartilage model develops
Figure 6.11

37. Stages of Endochondral Ossification
Cartilage calcifies and a periosteal bone collar forms around diaphysis
Figure 6.11

38. Stages of Endochondral Ossification
Primary ossification center forms in the diaphysis
Figure 6.11

39. Stages of Endochondral Ossification
Secondary ossification centers form in the epiphysis
Figure 6.11

40. Stages of Endochondral Ossification
Bone replaces cartilage, except the articular cartilage and epiphyseal plates
Figure 6.11

41. Stages of Endochondral Ossification
Epiphyseal plates ossify and form epiphyseal lines
Figure 6.11

42. The Epiphyseal Plate
A layer of hyaline cartilage at the boundary of the epiphysis and diaphysis
site of interstitial growth (bone lengthening)
consists of five distinct microscopic zones
Figure 6.12

43. Zones of Epiphyseal Plate
Zone of resting cartilage–farthest from medullary cavity, nearest epiphysis, small chondrocytes in hyaline cartilage
Figure 6.12

44. Zones of Epiphyseal Plate
Zone of proliferating cartilage–larger chondrocytes undergoing rapid mitotic cell division, aligned like stacks of coins
Figure 6.12

45. Zones of Epiphyseal Plate
Zone of hypertrophic cartilage– chondrocytes not dividing, become enlarged
Figure 6.12

46. Zones of Epiphyseal Plate
Zone of calcified cartilage–deposited minerals kill the chondrocytes and make matrix opaque
Figure 6.12

47. Zones of Epiphyseal Plate
Zone of ossification–walls between lacunae break, forming channels that become invaded with capillaries and osteoprogenitor cells
Figure 6.12

48. Bone Growth Bone is constantly being remodeled Two types of growth:
more dense in early adulthood, less in older adults
Two types of growth:
Interstitial: in length
Appositional: in diameter

49. Appositional Growth
Figure 6.13

50. Blood and Nerve Supply Three major types of arteries and veins:
Nutrient: supply the diaphysis; nerves usually accompany these into the shaft of the bone
Metaphyseal: supply area between the diaphysis and tepiphysis
Epiphyseal: supply cells in epiphyseal plate

51. Arterial Supply to Bone
Figure 6.14

52. Effects of Hormones and Vitamins on Bone

53. Effects of Exercise on Bone
Mechanical stress (i.e., muscle contraction and gravity) stimulates increase in bone density by increased osteoblast activity
Athletes who engage in these types of activities, on average, have greater bone density

54. Bone Fractures
Figure 6.15

55. Bone Fracture Classification

56. Bone Fracture Repair A bone fracture hematoma (blood clot) occurs.
A fibrocartilaginous (soft) callus forms.
A bony (hard) callus replaces the soft callus.
The bone is remodeled.

57. Bone Fracture Repair
Figure 6.16

58. Anatomical Features of Bones
Figure 6.17

59. Bone Aging During aging, bone changes in two ways:
Loses ability to produce organic matrix (mainly collagen)
loses Ca++ and other bone salts
This can result in a condition called osteoporosis, decrease in bone density
can result in bone fractures

60. Normal vs. Osteoporotic Bone