Chapter 32, Problem 20A

Summary Introduction

Introduction:

A point where two bones meet or join is known as joints. Joints are classified based on the structure and the movement they can allow. There are five types of joints in the human body. They are ball and socket, pivot, hinge, gilding and sutures.

Answer to Problem 20A

Correct answer:

The correct answer is option (b) wrist −pivot joints.

Explanation of Solution

Explanation/justification for the correct answer:

Option (b) wrist −pivot joints. Pivot joints are present in the elbow where the radius and ulna meets. The pivot joint provides a rotatory type of movement. In wrist gliding joints are present. Thus, the wrist −pivot joint is a mismatch.

Explanation for incorrect answer:

Option (a) cranium −sutures. The cranium is a part of the skull that protects the brain. In the skull, sutures type of joint is present. This joint doesn’t allow any type of movement. There are 22 bones in the skull and all are joined by the suture type of joint. Thus it is correctly matched.

Option (c) shoulder −ball and socket. In ball and socket type of joint, a ball-like surface of one bone fits into a cup-like depression of another bone. Ball and socket joints provide a wide range of movements and are present in the hips and shoulders. Thus, it is correctly matched.

Option (d) knee −hinge joint. In hinge joint convex surface of one bone gets fits into the concave surface of another bone. These types of joints provide back and forth movement and are present in the knee and elbow. Thus, it is correctly matched.

Conclusion

In wrist gliding joints are present and pivot joints are present in the elbow where radius and ulna meet. Thus, Option (b) wrist −pivot joints is a correct answer as it is mismatched.