8. 1 Introduction Functions of joints include (p. 261)

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Chapter 8

Joints of the Skeletal System

8.1 Introduction

1. Functions of joints include ____________ (p. 261)

e. all of the above.

8.2 Classification of Joints

2. Describe how joints are classified. (p. 261)

The type of tissue that binds the bones together at each junction can classify joints. They can also be classified according to the degree of movement possible at the bony junctions.

3. Compare the structure of a fibrous joint with that of a cartilaginous joint. (p. 261)

A fibrous joint uses fibrous connective tissue to hold bones together that are in close contact with one another. A cartilaginous joint uses hyaline or fibrocartilage to hold the articulation together. Neither type allows much movement.

4. A ___________ is a fibrous joint with bones bound by long connective tissue fibers, whereas a _____________ is a fibrous joint where flat bones are united by a thin layer of connective tissue.

(p. 261)

syndesmosis, suture

5. Describe a gomphosis, and name an example. (p. 262)

A gomphosis is a joint formed by the union of a cone-shaped bony process in a bony socket. The peg-like root of a tooth fastened to a jawbone by a periodontal ligament is such a joint.

6. Compare the structures of a synchondrosis and a symphysis. (p. 262)

A synchondrosis uses bands of hyaline cartilage to unite to bones. Many of these joints are temporary structures that disappear during growth. This particular type of joint allows no movement. A symphysis has the articular surfaces of bones covered with hyaline cartilage that is attached to a pad of fibrocartilage. This particular type of joint allows a limited type of movement.

7. Explain how the joints between vertebrae permit movement. (p. 262)

Each of these is a symphysis joint. Between each pair of vertebra there is an intervertebral disk that is composed of a band of fibrocartilage that surrounds a gelatinous core. The disk absorbs shocks and helps equalize pressure between the vertebrae during body movement. As each disk is slightly flexible, the combined movements of many of the joints in the vertebral column allow the back to bend forward, to the side, or to twist.

8.3 General Structure of a Synovial Joint

8. Draw the general structure of a synovial joint, labeling all the main parts. (p. 263)

A synovial joint will include the following components:

a. Articular cartilage—thin layer of hyaline cartilage on the ends of the articulating bones.

b. Joint capsule—tubular structure that has two distinct layers. The outer layer is made up of dense fibrous connective tissue. The inner layer is a shiny vascular membrane called the synovial membrane.

c. Synovial fluid—a clear viscous fluid secreted by the synovial membrane for lubrication of the joint.

d. Ligaments—bundles of tough collagenous fibers that serve to reinforce the joint capsule.

e. Menisci—disks of fibrocartilage found in some synovial joints that serve as shock absorbers.

f. Bursae—fluid-filled sacs that cushion and aid the movement of tendons within a synovial joint.

9. Describe how a joint capsule may be reinforced. (p. 264)

Ligaments are used to bind the articular ends of bones together reinforcing the joint capsule. These can be thickenings in the fibrous layer of the joint capsule or accessory structures that are located outside of the joint capsule.
10. Explain the function of the synovial membrane. (p. 264)

The synovial membrane covers all surfaces within the joint capsule, except the areas the articular cartilage covers. It fills spaces and irregularities within the cavity. It secretes synovial fluid. It may store adipose tissue. It also reabsorbs the synovial fluid.

11. Explain the function of synovial fluid. (p. 264)

Synovial fluid helps to cushion, moisten, and lubricate the smooth cartilaginous surfaces within the joint. It also supplies the articular cartilage with nutrients.
12. Define meniscus. (p. 265)

A meniscus is a disk of fibrocartilage that occurs in some synovial joints dividing them into two compartments. It serves as a shock absorber and allows bony prominences to fit together easier.

13. Define bursa. (p. 265)

A bursa is a fluid-filled sac associated with freely moveable joints.

8.4 Types of Synovial Joints

14. Describe the six types of synovial joints, and name an example of each type. (p. 265)

Type: Example:

Ball-and-Sockethip joint, shoulder joint

Condyloid joints between the metacarpals and phalanges

Gliding— joints between the various bones of the wrist and ankle

Hinge— elbow joint, knee joint

Pivot—joint between the proximal end of the radius and ulna

Saddle—joint between the carpal and metacarpal of the thumb
15. Describe the movements permitted by each type of synovial joint. (p. 265)

Type of Movement

Ball-and-Socketmovement in all planes, as well as rotational movement around a central axis

Condyloid— variety of movement in different planes, but rotational movement is possible

Gliding—sliding back and forth motion only

Hinge— flexion and extension in one plane only

Pivot— rotation around a central axis only

Saddle— variety of movements
8.5 Types of Joint Movements

16. Joint movements occur when a muscle contracts and the muscle fibers pull the muscle’s movable end of attachment, the ___________, toward its fixed end, the _________________. (p. 267)

insertion, origin

17. Match the movements on the left with the descriptions listed on the right. (pp. 267-270)

1. Rotation D—moving part around an axis

2. Supination A—turning palm upward

3. Extension G—increasing angle between parts

4. Eversion F—turning the foot so the plantar surface faces laterally

5. Protraction C—moving part forward

6. Flexion B—decreasing angle between parts

7. Pronation I—turning palm downward

8. Abduction J—moving part away from midline

9. Depression H—lowering a part

10. Adduction E—moving part toward midline
8.6 Examples of Synovial Joints

18. Name the parts that comprise the shoulder joint. (p. 271)

The shoulder joint consists of the head of the humerus and the glenoid cavity of the scapula.

19. Name the major ligaments associated with the shoulder joint. (p. 271)

Coracohumeral ligament—connects the coracoid process of the scapula to the greater tubercle of the humerus.

Glenohumeral ligament—three binds of fibers that appear as thickenings in the ventral wall of the joint capsule and extend from the edge of the glenoid fossa to the lesser tubercle and the anatomical neck of the humerus.

Transverse humeral ligament—runs between the greater and lesser tubercles of the humerus.

Glenoidal labrum—attached along the margin of the glenoid fossa and forms a rim with a thick free edge that deepens the fossa.
20. Explain why the shoulder joint permits a wide range of movements. (p. 271)

The shoulder joint permits a wide range of movements due to the looseness of it attachments and the relatively large articular surface of the humerus compared to the shallow depth of the glenoid fossa. The movements include flexion, extension, abduction, adduction, rotation, and circumduction.

21. Name the parts that comprise the elbow joint. (p. 272)

The elbow joint includes the trochlea of the humerus, the trochlear notch of the ulna, the capitulum of the humerus, and a fovea on the head of the radius.

22. Name the major ligaments associated with the elbow joint. (p. 272)

Radial collateral ligament—connects the lateral epicondyle of the humerus to the annular ligament of the radius.

Annular ligament—connects the margin of the trochlear notch of the ulna and encircles the head of the radius.

Ulnar collateral ligament—connects the medial epicondyle of the humerus to the medial margin of the coronoid process. It also connects posteriorly to the medial epicondyle of the humerus and to the olecranon process of the ulna.
23. Describe the movements permitted by the elbow joint. (p. 273)

The only movements permitted between the humerus and ulna is flexion and extension. The head of the radius, however, is free to rotate in the annular ligament, which allows pronation and supination of the hand.

24. Name the parts that comprise the hip joint. (p. 274)

The hip joint consists of the head of the femur and the cup-shaped acetabulum of the coxal bone.

25. Describe how the articular surfaces of the hip joint are held together. (p. 274)

Acetabular labrum—horseshoe-shaped ring of fibrocartilage at the rim of the acetabulum deepens the acetabular cavity and encloses the head of the femur.

Iliofemoral ligament—connects the anterior inferior iliac spine of the coxal bone to the intertrochanteric line between the greater and lesser trochanters of the femur.

Pubofemoral ligament—extends between the superior portion of the pubis and the iliofemoral ligament.

Ischiofemoral ligament—originates on the ischium just posterior to the acetabulum and blends with the fibers of the joint capsule.
26. Explain why there is less freedom of movement in the hip joint than in the shoulder joint. (p. 274)

Muscles surround the joint capsule of the hip. The articulating parts of the hip are held more closely together than those of the shoulder, allowing considerably less freedom of movement.

27. Name the parts that comprise the knee joint. (p. 274)

The knee joint consists of the medial and lateral condyles at the distal end of the femur, and the medial and lateral condyles at the proximal end of the tibia. The femur also articulates anteriorly with the patella.

28. Describe the major ligaments associated with the knee joint. (p. 274)

Patellar ligament—continuation of a tendon from the quadriceps muscle group that extends from the margin of the patella to the tibial tuberosity.

Oblique popliteal ligament—connects the lateral condyle of the femur to the margin of the head of the tibia.

Arcuate popliteal ligament—extends from the lateral condyle of the femur to the head of the fibula.

Tibial collateral ligament (medial collateral ligament)—connects the medial condyle of the femur to the medial condyle of the tibia.

Fibular collateral ligament (lateral collateral ligament)—connects the lateral condyle of the femur and the head of the fibula.

Anterior cruciate ligament (ACL)—originates from the anterior intercondylar area of the tibia and extends to the lateral condyle of the femur.

Posterior cruciate ligament (PCL)—connects the posterior intercondylar area of the tibia to the medial condyle of the femur.
29. Explain the function of the menisci of the knee. (p. 276)

The menisci serve as shock absorbers. They also function to compensate for the differences in shapes between the surfaces of the femur and tibia.

30. Describe the locations of the bursae associated with the knee joint. (p. 276)

Suprapatellar bursa—located between the anterior surface of the distal end of the femur and the quadriceps muscle group above it.

Prepatellar bursa—located between the patella and the skin.

Infrapatellar bursa—located between the proximal end of the tibia and the patellar ligament.
8.7 Life-Span Changes

31. Describe the process of aging as it contributes to the stiffening of fibrous, cartilaginous, and synovial joints. (p. 279)

Joint stiffness is often the earliest sign of aging.

a. Collagen changes cause the feeling of stiffness.

b. Regular exercise can lessen the effects.

Fibrous joints are the first to begin to change and strengthen over a lifetime.

Synchondroses of the long bones disappear with growth and development.

Changes in symphysis joints of the vertebral column diminish flexibility and decrease height.

Over time, synovial joints lose elasticity.

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