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CHAPTER
6
Bones and Skeletal Tissues
Objectives
Skeletal Cartilages
1. Describe the functional properties of the three types of cartilage tissue.
Classification of Bones
4. Name the major regions of the skeleton and describe their relative functions.
Functions of Bones
6. List and describe seven important functions of bones.
Bone Structure
7. Describe the gross anatomy of a typical flat bone and a long bone. Indicate the locations
and functions of red and yellow marrow, articular cartilage, periosteum, and endosteum.
Bone Development
11. Compare and contrast intramembranous ossification and endochondral ossification.
Bone Homeostasis: Remodeling and Repair
13. Compare the locations and remodeling functions of the osteoblasts, osteocytes, and
osteoclasts.
Homeostatic Imbalances of Bone
16. Contrast the disorders of bone remodeling seen in osteoporosis, osteomalacia, and
Paget’s disease.
Developmental Aspects of Bones: Timing of Events
17. Describe the timing and cause of changes in bone architecture and bone mass throughout
life.
Suggested Lecture Outline
I. Skeletal Cartilages (pp. 173–174; Fig. 6.1)
A. Basic Structure, Types, and Locations (pp. 173–174; Fig. 6.1)
1. Skeletal cartilages are made from cartilage, surrounded by a layer of dense irregular
connective tissue called the perichondrium.
B. Growth of Cartilage (p. 174)
1. Appositional growth results in outward expansion due to the production of cartilage
matrix on the outer face of the tissue.
2. Interstitial growth results in expansion from within the cartilage matrix due to division
of lacunae-bound chondrocytes and secretion of matrix.
II. Classification of Bones (pp. 174–176; Figs. 6.1–6.2)
A. There are two main divisions of the bones of the skeleton: the axial skeleton, and the
appendicular skeleton. (pp. 174–175; Fig. 6.1)
tach them to the axial skeleton.
B. Shape (pp. 175–176; Fig. 6.2)
1. Long bones are longer than they are wide, have a definite shaft and two ends, and
consist of all limb bones except patellas, carpals, and tarsals.
III. Functions of Bones (pp. 176–177)
A. Bones support the body, surround and protect soft or vital organs, allow movement, store
minerals such as calcium and phosphate, house hematopoietic tissue and fat in specific
marrow cavities, and produce hormones (pp. 176–177).
IV. Bone Structure (pp. 177–183; Figs. 6.3–6.7; Table 6.1)
A. Gross Anatomy (pp. 177–179; Figs. 6.3–6.4; Table 6.1)
1. Bone markings are projections, depressions, and openings found on the surface of
2. Bone Textures: Compact and Spongy Bone
a. All bone has a dense outer layer consisting of compact bone that appears smooth
and solid.
b. Internal to compact bone is spongy bone, which consists of honeycomb, needle-
like, or flat pieces, called trabeculae.
3. Structure of Short, Irregular, and Flat Bones
4. Structure of a Typical Long Bone
a. Long bones have a tubular diaphysis, consisting of a bone collar surrounding a
hollow medullary cavity, which is filled with yellow bone marrow in adults.
5. Location of Hematopoietic Tissue in Bones
a. Red bone marrow is located within the trabecular cavities of the spongy bone in
1. Bone tissue contains five types of cells: bone stem cells, called osteogenic cells,
osteoblasts that secrete bone matrix, osteocytes and bone lining cells that monitor and
maintain bone matrix, and osteoclasts that are involved in bone resorption.
2. The structural unit of compact bone is the osteon, or Haversian system, a series of
concentric tubes of bone matrix (the lamellae) surrounding a central Haversian canal
that serves as a passageway for blood vessels and nerves.
3. Spongy bone lacks osteons but has trabeculae that align along lines of stress, which
contain irregular lamellae and osteocytes connected with canaliculi.
C. Chemical Composition of Bone (pp. 182–183)
1. Organic components of bone include cells and osteoid (ground substance and collagen
fibers), which contribute to the flexibility and tensile strength of bone.
V. Bone Development (pp. 183–187; Figs. 6.8–6.11)
A. Formation of the Bony Skeleton (pp. 183–185; Figs. 6.8–6.9)
1. In endochondral ossification, bone tissue replaces hyaline cartilage, forming all bones
below the skull except for the clavicles.
a. Initially, osteoblasts secrete osteoid, creating a bone collar around the diaphysis of
2. Intramembranous ossification forms membrane bone from fibrous connective tissue
membranes, and results in the cranial bones and clavicles.
B. Postnatal Bone Growth (pp. 185–187; Figs. 6.10–6.11)
1. Growth in length of long bones occurs at the ossification zone through the rapid divi-
sion of the upper cells in the columns of chondrocytes, calcification and deterioration
of cartilage at the bottom of the columns, and subsequent replacement by bone tissue.
VI. Bone Homeostasis: Remodeling and Repair (pp. 187–192; Figs. 6.12–6.15;
Table 6.2)
A. Bone Remodeling (pp. 187–191; Figs. 6.12–6.14)
1. In adult skeletons, bone deposit and resorption occur beneath the periosteum and
endosteum; bone remodeling is balanced bone deposit and resorption.
2. Control of Remodeling
a. Hormonal control of remodeling is mostly used to maintain blood calcium
B. Bone Repair (pp. 191–192; Fig. 6.15; Table 6.2)
1. Fractures are breaks in bones and are classified by: the position of the bone ends after
fracture, completeness of break, and whether the bone ends penetrate the skin.
VII. Homeostatic Imbalances of Bone (pp. 192–193; Fig. 6.16)
A. Osteomalacia and Rickets (p. 192)
1. Osteomalacia includes a number of disorders in adults in which the bone is inade-
quately mineralized.
B. Osteoporosis refers to a group of disorders in which the rate of bone resorption exceeds
the rate of formation (pp. 192–193, Fig. 6.16).
1. Bones have normal bone matrix, but bone mass is reduced and the bones become more
porous and lighter, increasing the likelihood of fractures.
C. Paget’s disease is characterized by excessive bone deposition and resorption, with the
resulting bone abnormally high in spongy bone. It is a localized condition that results in
deformation of the affected bone (p. 193).
VIII. Developmental Aspects of Bones: Timing of Events (pp. 193–194; Fig. 6.17)
A. The skeleton derives from embryonic mesenchymal cells, with ossification occurring at
precise times. Most long bones have obvious primary ossification centers by 12 weeks
after conception (p. 193; Fig. 6.17).
Cross References
Additional information on topics covered in Chapter 6 can be found in the chapters listed below.
1. Chapter 2: Calcium salts
2. Chapter 4: Bone (osseous tissue); chondroblasts; collagen fibers; fibroblasts; fibrocarti-
Lecture Hints
1. Students often erroneously distinguish between long and short bones on the basis of size.
Stress that the distinction is based on shape, not size.
6. Compare and contrast the location and function of osteocytes, osteoblasts, and
osteoclasts.
7. Point out that long bone growth ends sooner in females (18 years) than in males
(21 years).
Activities/Demonstrations
1. Audiovisual materials are listed in the Multimedia in the Classroom and Lab section of
this Instructor Guide (p. 387).
4. Obtain a sectioned long bone, such as a femur, to illustrate major parts of a bone. A fresh
sectioned bone could be used to illustrate the periosteum and the difference between red
and yellow marrow.
7. Obtain X rays of young children, teenagers, and adults to illustrate changes in the epi-
physeal plate.
8. Obtain X rays of various types of fractures. If possible, obtain X rays that illustrate
healing stages following the fracture.
Critical Thinking/Discussion Topics
1. Explore the statement, “Multiple pregnancies will result in the mother losing all the
enamel from her teeth and calcium from her bones.” Is this all true, all false, or only
partly true?
5. Full-contact sports seem to be a part of the curriculum for primary-school-age children.
In terms of bone development, is this wise?
6. Prehistoric remains of animals consist almost exclusively of bones and teeth. Why?
7. If bone tissue is so hard, how can we move teeth from one location in the jaw to another?
these effects be minimized or at least reduced?
Library Research Topics
1. Research the latest technique, such as the Ilizarov procedure, used to lengthen bones
damaged in accidents or illnesses.
4. Explore the procedures used in bone tissue transplants where pieces of bone are removed
from one part of the body and implanted into another.
5. What effect would steroid use have on the bone tissue and bone marrow?
List of Figures and Tables
All of the figures in the main text are available in JPEG format, PPT, and labeled & unlabeled
format on the Instructor Resource DVD. All of the figures and tables will also be available in
Transparency Acetate format. For more information, go to www.pearsonhighered.com/educator.
two thin layers of compact bone.
Figure 6.4 The structure of a long bone (humerus of arm).
Figure 6.5 Comparison of different types of bone cells.
Figure 6.6 A single osteon.
Figure 6.7 Microscopic anatomy of compact bone.
Figure 6.8 Endochondral ossification in a long bone.
Figure 6.9 Intramembranous ossification.
Answers to End-of-Chapter Questions
Multiple-Choice and Matching Question answers appear in Appendix H of the main text.
Short Answer Essay Questions
15. Cartilage has greater resilience than bone because its matrix lacks the bone salts found in
bone tissue. Regeneration is much faster and more complete in bone tissue because it has
16. a. In endochondral ossification, a bony collar is laid down around the diaphysis of the
hyaline cartilage model.
b. Nutrient delivery to the cartilage in the center of the diaphysis is hindered, causing
17. Peforating canals radiate throughout the bone matrix, linking the central canal, perio-
steum, and all lamellae. Canaliculi interconnect all lacunae, allowing transfer of nutrients
and wastes between the blood and osteocytes. (p. 181)
18. The increase in thickness of compact bone on its superficial face is counteracted by the
resorption of bone by osteoclasts on its internal surface. (p. 187)
19. In an adult bone, new bone tissue is formed when osteoblasts deposit new bone matrix,
forming an osteoid seam, a layer of unmineralized bone matrix. A calcification front,
20. Two control loops regulate bone remodeling. A hormonal mechanism involving PTH that
maintains blood Ca2+ promotes increased breakdown of bone matrix, while mechanical
21. a. Skeletal mass increases the most during the first decade of life, and begins to decline
during the fourth decade of life. (p. 193)
22. This bone section is taken from the diaphysis of the specimen. The presence of an osteon, the
concentric layers surrounding a central cavity, indicates compact bone found in the diaphysis.
The epiphyseal plate, the site of active bone growth, lacks osteons. (pp. 181, 184)
Critical Thinking and Clinical Application Questions
1. A bony callus is tissue formed when the fibrocartilaginous callus is converted to a callus
containing trabeculae of spongy bone. (p. 191)
2. Rickets. Milk provides dietary calcium and vitamin D. Vitamin D is needed for its uptake
by intestinal cells; the sun helps the skin synthesize vitamin D. Thick epiphyseal plates
3. The compact lamellar structure of dense bone produces structural units designed to resist
twisting and other mechanical stresses placed on bones. In contrast, spongy bone is made
4. The changes in bone development throughout adolescence are driven by changes in
levels of sex steroids, as well as stress associated with muscle growth. A lack of bone
5. According to Wolff’s law, bone growth and remodeling occur in response to stress
placed on such bones. With disuse, the bones in the paralyzed limbs will begin to
atrophy. (p. 189)
6. It is likely that he has suffered an epiphyseal fracture, in which the epiphyseal plate-bone
7. Paget’s disease, which results in irregular thickening of bone tissue and often affects the
skull and spine, causing pain and deformity. (p. 193)
Suggested Readings
Arron, Joseph R., and Yongwon Choi. “Bone Versus Immune System.” Nature 408 (6792)
(July 2000): 535–536.
Cheng, F., and P. Hulley. “The Osteocyte—A Novel Endocrine Regulator of Body Phosphate
Homeostasis.” Maturitas 67 (4) (Sept. 2010): 327–338.
Manolagas, S. C. “Birth and Death of Bone Cells: Basic Regulatory Mechanisms and Impli-
cations for the Pathogenesis and Treatment of Osteoporosis.” Endocrine Reviews 21 (2)
(April 2000): 115–137.
Quarto, R., et al. “Repair of Large Bone Defects with the Use of Autologous Bone Marrow
Stromal Cells.” New England Journal of Medicine 344 (5) (Feb. 2001): 385–386.
