Joints and Their Classification

Objectives

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

• explain what joints are, how they are named, and what functions they serve;
• define arthrology, kinesiology, and biomechanics; and
• name and describe the three major structural classes and three major functional classes of joints.

Key Point Review

1. What joins two bones together at synovial, fibrous, and cartilaginous joints? Give one example of each.

2. Which type of joint is a diarthrosis-synovial, fibrous, or cartilaginous?

Fibrous, Cartilaginous, and Bony Joints

Objectives

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

• describe the three types of fibrous joints and give an example of each;
• distinguish between the three types of sutures;
• describe the two types of cartilaginous joints and give an example of each; and
• name some joints that become synostoses as they age.

Think About It

The intervertebral joints are symphyses only in the thoracic through the lumbar region. How would you classify the intervertebral joints of the sacrum and coccyx in a middle-aged adult?

Key Point Review

3. Define suture, gomphosis, and syndesmosis, and explain what these three joints have in common.

4. Name the three types of sutures and describe how they differ.

5. Name two synchondroses and two symphyses.

6. Give some examples of joints that become synostoses with age.

Form and Function of Synovial Joints

Objectives

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

• describe the anatomy of a synovial joint and its associated structures;
• describe the six types of synovial joints;
• list and demonstrate the types of movements that occur at diarthroses;
• discuss the factors that affect the range of motion of a joint;
• give an anatomical example of a first-, second-, and third-class lever and explain why each is classified as it is; and
• relate the concept of mechanical advantage to the power and speed of joint action.

Think About It

Some synovial joints have articular surfaces or ligaments that prevent them from being hyperextended. Try hyperextending some of your synovial joints and list a few for which this is impossible.

Think About It

A chimpanzee sitting on the ground reaches out and grasps an object between its fingertips. Then it raises its hand to its face and turns the object to examine it. List the diarthrotic movements that would occur and identify the joint at which each one would occur.

Key Point Review

7. What are the two components of a joint capsule? What is the function of each?

8. What types of joints are described as monaxial, biaxial, and multiaxial? Give an example of each and explain the eason for its classification.

9. Name the joints that would be involved if you reached directly overhead and screwed a lightbulb into a ceiling fixture. Describe the joint actions that would occur.

10. Where are the effort, fulcrum, and resistance in the act of dorsiflexion? What class of lever is this? Would you expect it to have a mechanical advantage greater or less than 1.0? Why?

Anatomy of Selected Diarthroses

Objectives

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

• identify the major anatomical features of the jaw, shoulder, elbow, hip, knee, and ankle joints; and
• explain how the anatomical differences between these joints are related to differences in function.

Think About It

Comment on this proposition from the standpoint of human evolution and functional anatomy: There would be no professional baseball players if Homo sapiens had not descended from arboreal primates.

Key Point Review

11. What keeps the mandibular condyle from slipping out of its fossa in a posterior direction?

12. Explain how the biceps tendon braces the shoulder joint.

13. What structure elsewhere in the skeletal system has a structure and function similar to the acetabular labrum of the os coxae?

14. What keeps the femur from slipping backward off the tibia?

15. What keeps the tibia from slipping sideways off the talus?

Copyright ©1998 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use and Privacy Policy.
McGraw-Hill Higher Education is one of the many fine businesses of The McGraw-Hill Companies.
For further information about this site contact mhhe_webmaster@mcgraw-hill.com.