Tissues and Organs of the Skeletal System

Objectives

When you have completed this section, you should be able to

• summarize the organs and tissues that constitute the skeletal system;
• defend the argument that osseous tissue is not inert but a living, dynamic tissue with numerous functions;
• distinguish between bone as a tissue and as an organ; and
• state the number of bones in a typical adult skeleton and explain the reasons for deviations from this number.

Key Point Review

1. Distinguish between osseous tissue and a bone.

2. Name any five tissues found in a bone.

3. List at least three functions of the skeletal system besides physical support and protection.

4. Explain why the number of bones changes with age.

Gross Anatomy of Bones

Objectives

When you have completed this section, you should be able to

• describe the four major groups of bones as classified by shape and function; and
• define terms that describe the structural features of bones.

Key Point Review

5. Name the four shapes of bones and give one example of each.

6. What is the difference between compact and spongy bone, and what is their spatial relationship to each other?

7. State the anatomical terms for the shaft, head, growth zone, and fibrous covering of a long bone.

8. Concisely define condyle, process, tubercle, fossa, and foramen.

Histology of Osseous Tissue

Objectives

When you have completed this section, you should be able to

• list and describe the cells, fibers, and ground substance of osseous tissue and state the importance of each constituent;
• compare the two types of osseous tissue with respect to their histology; and
• distinguish between the three types of bone marrow.

Think About It

What two organelles do you think are especially prominent in osteoblasts? (Hint: Consider the major substances osteoblasts synthesize.)

Key Point Review

9. If you had electron micrographs of the four kinds of bone cells and their neighboring tissue, how would you ascertain which was which? Name the four cell types in your answer.

10. What are three organic constituents of the bone matrix?

11. What are the mineral crystals of osseous tissue called, and what are they made of?

12. Sketch a cross section of an osteon and label its major parts.

13. List the names of the three kinds of bone marrow and state where each is found. Which one is a hemopoietic tissue? What does this mean?

Bone Development

Objectives

When you have completed this section, you should be able to

• describe two methods of bone formation (ossification); and
• explain how the growth and remodeling of mature bones occurs.

Think About It

In a given osteon, which lamellae are the oldest–those immediately adjacent to the haversian canal or those around the perimeter of the osteon?

Key Point Review

14. Describe the sequence of events that occurs in intramembranous ossification.

15. List the five zones of a metaphysis and describe the major event(s) that occur in each one.

16. Describe the major gross features of a long bone at the time of birth.

17. Use a sketch to describe the process of appositional bone growth.

Physiology of Osseous Tissue

Objectives

When you have completed this section, you should be able to

• explain how bone becomes mineralized and how the minerals are removed;
• discuss the role of bones in regulating blood levels of calcium and phosphorus;
• explain how vitamin D is synthesized and describe its effects on the skeleton; and
• list the hormones that influence the formation and resorption of bone and briefly describe the effects of each.

Think About It

Parathyroid hormone does not promote intestinal absorption of phosphate. Explain why it would defeat the purpose of PTH to do so.

Key Point Review

18. How are collagen and seed crystals relevant to bone mineralization?

19. Why must blood calcium levels be kept within such a narrow range?

20. What effect does calcitonin have on blood calcium, and how does it achieve this effect?

21. What effect does parathyroid hormone have on blood calcium, and how does it achieve this effect?

22. Explain how vitamin D is synthesized and how it exerts an influence on blood calcium concentration.

Bone Disorders

Objectives

When you have completed this section, you should be able to

• describe the various types of fractures;
• explain how a fracture is repaired; and
• discuss some clinical treatments for fractures and other skeletal disorders.

Key Point Review

23. Name and describe at least five types of fractures.

24. Why would osteomyelitis be more likely to occur in an open fracture than a closed fracture?

25. What is a callus? How does it contribute to fracture repair?

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