1. Bones and Skeletal Tissues
Chapter 6

2. Skeletal Cartilages Contain no blood vessels or nerves
Perichondrium (dense irregular connective tissue girdle) contains blood vessels for nutrient delivery to cartilage
Types
Hyaline
Elastic
Fibrocartilage

3. Respiratory tube cartilages in neck and thorax
Epiglottis
Larynx
Thyroid
cartilage
Cartilage in
external ear
Cartilages in
nose
Trachea
Cricoid
cartilage
Lung
Articular
Cartilage
of a joint
Cartilage in
Intervertebral disc
Costal
cartilage
Respiratory tube cartilages
in neck and thorax
Pubic
symphysis
Bones of skeleton
Axial skeleton
Meniscus (padlike
cartilage in
knee joint)
Appendicular skeleton
Cartilages
Articular cartilage
of a joint
Hyaline cartilages
Elastic cartilages
Fibrocartilages
Figure 6.1

4. Growth of Cartilage Appositional
Cells secrete matrix against the external face of existing cartilage
Interstitial
Chondrocytes divide and secrete new matrix, expanding cartilage from within

5. Bones of the Skeleton Cartilage in Cartilages in external ear nose
Articular
Cartilage
of a joint
Cartilage in
Intervertebral disc
Costal
cartilage
Pubic
symphysis
Meniscus (padlike
cartilage in
knee joint)
Articular cartilage
of a joint
Figure 6.1

6. Classification of Bones by Shape
Long bones
Short bones
Flat bones
Irregular bones

7. Functions of Bones Support Protection Movement
Mineral & Growth Factor Storage
Blood cell formation
Triglyceride storage
Hormone Production

8. Bone Structure Bones are organs! Multiple tissue types
Bone (osseous) tissue, nervous tissue, cartilage, fibrous connective tissue, muscle and epithelial cells (in its blood vessels)

9. Bone Texture Compact Spongy (trabecular)
Dense outer layer; smooth and solid
Spongy (trabecular)
Honeycomb of flat pieces of bone (trabeculae) deep to compact
Space b/w trabeculae filled with red or yellow bone marrow

10. Structure of Short, Irregular, and Flat Bones
Periosteum covered compact bone on the outside
Endosteum covered spongy bone within
diploë
Bone marrow b/w the trabeculae
Hyaline cartilage on articular surfaces

11. Structure of Typical Long Bone
Diaphysis
Tubular shaft forms long axis
Compact bone surrounds medullary cavity
Epiphyses (bone ends)
Compact bone outside; spongy bone inside
Articular cartilage covers articular surfaces
Epiphyseal line
b/w diaphysis and epiphysis
Remnant of epiphyseal plate

13. Membranes of Bone Periosteum Outer fibrous layer
Inner osteogenic layer
Contains nerve fibers, nutrient blood vessels, and lymphatic vessels that enter the bone via nutrient foramina
Secured to underlying bone by Sharpey’s fibers

14. Membranes of Bone Endosteum
Delicate membrane on internal surfaces of bone
Contains osteogenic cells

15. Hematopoietic Tissue (Red Marrow)
Infants (long bones)
Medullary cavities and spongy bone
Adults (long bones)
Little red marrow
Red marrow in flat and some irregular bones is most active

16. Bone Markings Projections, depressions, and holes
Sites of attachment for muscles, ligaments, and tendons
Joint surfaces
Passageways for blood vessels and nerves

17. Bone Markings: Projections
Sites of muscle and ligament attachment
Tuberosity
Crest
Trochanter
Line
Tubercle
Epicondyle
Spine
Process
Projections that help to form joints
Head
Facet
Condyle
Ramus

18. Bone Markings: Depressions and Openings
Passages for blood vessels and nerves
Meatus
Sinus
Fossa
Groove
Fissure
Foramen

19. Microscopic Anatomy of Bone

20. Microscopic Anatomy of Bone: Compact Bone
Haversian system (or osteon)
Lamellae
Central (Haversian) canal

21. Microscopic Anatomy of Bone:
Compact Bone
Perforating (Volkmann’s) canals
Lacunae
Canaliculi

22. Microscopic Anatomy of Bone: Spongy Bone
Trabeculae
Align along lines of stress
No osteons
Irregularly arranged lamellae, osteocytes, and canaliculi
Capillaries in endosteum supply nutrients

23. Chemical Composition of Bone
Organic
Bone cells
Osteoid—organic bone matrix secreted by osteoblasts
Ground substance, collagen fibers
Inorganic
Hydroxyapatites (mineral salts)
65% of bone by mass
Mainly calcium phosphate crystals

24. Bone Development
Ossification (osteogenesis): process of bone tissue formation
Formation of bony skeleton
Begins in 2nd month of development
Postnatal bone growth
Until early adulthood
Bone remodeling and repair
Lifelong

25. Types of Ossification Endochondral ossification
Bone forms by replacing hyaline cartilage
Majority of skeleton
Intramembranous ossification
Bone develops from fibrous membrane
Bones called membrane bones
Forms flat bones, e.g. clavicles and cranial bones

26. Endochondral Ossification
Forms most all bones inferior to base of skull (except clavicles)
Begins late in 2nd month of development
Uses hyaline cartilage models
Hyaline cartilage must be broken down before ossification

27. Childhood to adolescence
Week 9
Month 3
Birth
Childhood to adolescence
Articular cartilage
Secondary ossification center
Spongy bone
Epiphyseal blood vessel
Area of deteriorating cartilage matrix
Epiphyseal plate cartilage
Hyaline cartilage
Medullary cavity
Spongy bone formation
Bone collar
Blood vessel of periosteal bud
Primary ossification center 1 2 3 4 5
Figure 6.9

28. Intramembranous Ossification
Forms cranial bones of the skull and clavicles
Begins within fibrous connective tissue membranes formed by mesenchymal cells
Ossification centers appear
Osteoid is secreted
Woven bone and periosteum form
Lamellar bone replaces woven bone & red marrow appears

29. Figure 6.9 Intramembranous ossification.
Mesenchymal
cell
Osteoblast
Osteoid
Collagen fibril
Ossification
center
Osteocyte
Newly
calcified
bone matrix
Osteoid
Osteoblast
1 Ossification centers appear in the fibrous
connective tissue membrane.
2 Osteoid is secreted within the fibrous membrane and
calcifies.
Fibrous
periosteum
Mesenchyme
condensing
to form the
periosteum
Osteoblast
Plate of
compact bone
Trabeculae of
woven bone
Diploë
(spongy bone)
cavities
contain red
marrow
Blood vessel
3 Woven bone and periosteum form.
4 Lamellar bone replaces woven bone, just deep to the
periosteum. Red marrow appears.
Figure 6.9 Intramembranous ossification.

30. Postnatal Bone Growth Interstitial growth: Appositional growth:
 length of long bones
Appositional growth:
 thickness and remodeling of all bones by osteoblasts and osteoclasts on bone surfaces

31. Interstitial (Longitudinal) Growth
Epiphyseal plate cartilage organizes into 5 important functional zones:
Resting (quiescent) zone
Proliferation (growth)
Hypertrophic
Calcification
Ossification (osteogenic)

32. Cartilage cells undergo mitosis.
Resting zone
Proliferation zone
Cartilage cells undergo
mitosis. 1
Hypertrophic zone
Older cartilage cells
enlarge. 2
Calcification zone
Matrix becomes calcified;
cartilage cells die; matrix
begins deteriorating. 3
Calcified cartilage
spicule
Osteoblast depositing
bone matrix
Ossification zone
New bone formation is
occurring.
Osseous tissue
(bone) covering
cartilage spicules 4
Figure 6.10

33. Appositional Growth Growth in Width Osteoblasts active in periosteum
Osteoclasts active in the endosteum
Building > Breaking down = thicker stronger bone

34. Bone growth Bone remodeling Articular cartilage Cartilage grows here.
Epiphyseal plate
Cartilage
is replaced
by bone here.
Bone is
resorbed here.
Cartilage
grows here.
Bone is added
by appositional
growth here.
Cartilage
is replaced
by bone here.
Bone is
resorbed here.
Figure 6.11

35. Hormonal Regulation of Bone Growth
Growth hormone
Thyroid hormone
Testosterone and Estrogen

36. Bone Remodeling Bone is constantly being “recycled”
surface of periosteum and endosteum
Deposit
Injury or needed strength, requires good diet
Osteoid seam and Calcification front
Resorption
Osteoclasts secrete: lysosomal enzymes, acids
Dissolved matrix is transcytosed

37. Control of Remodeling What controls continual remodeling of bone?
Hormonal mechanisms that maintain calcium homeostasis in the blood
Mechanical and gravitational forces

38. Hormonal Control of Blood Ca2+
Most calcium in the body is in the bones
Less that 1.5g in blood – tightly regulated narrow range
Calcium is necessary for
Transmission of nerve impulses
Muscle contraction
Blood coagulation
Secretion by glands and nerve cells
Cell division

39. Stimulus Thyroid gland Osteoclasts Parathyroid degrade bone glands
Calcium homeostasis of blood: 9–11 mg/100 ml
BALANCE
BALANCE
Stimulus
Falling blood
Ca2+ levels
Thyroid
gland
Osteoclasts
degrade bone
matrix and
release Ca2+
into blood.
Parathyroid
glands
Parathyroid
glands release
parathyroid
hormone (PTH).
PTH
Figure 6.12

40. Hormonal Control of Blood Ca2+
May be affected to a lesser extent by calcitonin
 Blood Ca2+ levels 
Parafollicular cells of thyroid release calcitonin
Osteoblasts deposit calcium salts
 Blood Ca2+ levels

41. Response to Mechanical Stress
Wolff’s law: A bone grows or remodels in response to forces or demands placed upon it

42. Hormones and Mechanical Stress
when remodeling occurs
As a response to what???
Mechanical Stress
Where the remodeling occurs

43. Classification of Bone Fractures
Bone fractures may be classified by four “either/or” classifications
Position of bone ends after fracture:
Nondisplaced or Displaced
Completeness of the break
Complete or Incomplete
Orientation of the break to the long axis of the bone:
Linear or transverse
Whether or not the bone ends penetrate the skin
Compound (open) or Simple (closed)

44. Common Types of Fractures
In addition to the previous classification, all fractures can be described in terms of
Location
External appearance
Nature of the break

45. Table 6.2

46. Table 6.2

47. Table 6.2

48. Fracture Healing
Hematoma forms
Fibrocartilaginous callus forms

49. Fracture Healing
Bony callus formation
Bone remodeling

50. Homeostatic Imbalances
Osteomalacia and Rickets
Calcium salts not deposited
Rickets (childhood disease) causes bowed legs and other bone deformities
Cause: vitamin D deficiency or insufficient dietary calcium

51. Homeostatic Imbalances
Osteoporosis
Loss of bone mass
Spongy bone of spine and neck of femur become most susceptible to fracture
Risk factors
Lack of estrogen, calcium or vitamin D; petite body form; immobility; low levels of TSH; diabetes mellitus; smoking

52. Developmental Aspects of Bones
Embryonic skeleton ossifies predictably so fetal age easily determined from X rays or sonograms
At birth, most long bones are well ossified (except epiphyses)

53. Developmental Aspects of Bones
Nearly all bones completely ossified by age 25
Bone mass decreases with age beginning in 4th decade
Rate of loss determined by genetics and environmental factors
In old age, bone resorption predominates