Objectives Classification of Joints

1. Define joint or articulation.

2. Classify joints structurally and functionally.

Fibrous Joints

3. Describe the general structure of fibrous joints. Name and give an example of each of the three common types of fibrous joints.

4. Describe the general structure of cartilaginous joints. Name and give an example of each of the two common types of cartilaginous joints.

5. Describe the structural characteristics of synovial joints.

6. Compare the structures and functions of bursae and tendon sheaths.

7. List three natural factors that stabilize synovial joints.

8. Name and describe (or perform) the common types of body movements.

9. Name and provide examples of the six types of synovial joints based on the type of movement(s) allowed.

10. Describe the elbow, knee, hip, jaw, and shoulder joints in terms of articulating bones, anatomical characteristics of the joint, movements allowed, and joint stability.

Homeostatic Imbalances of Joints

11. Name the most common joint injuries and discuss the symptoms and problems associated with each.

12. Compare and contrast the common types of arthritis.

13. Describe the cause and consequences of Lyme disease.

14. Discuss factors that promote or disturb joint homeostasis.

A. Structural classification focuses on the material binding the bones together and whether or not a joint cavity is present (p. 249; Table 8.1).

1. In fibrous joints the bones are joined together by fibrous tissue and lack a joint cavity.

2. In cartilaginous joints the bones are joined together by cartilage and they lack a joint cavity.

3. In synovial joints, the articulating bones are separated by a fluid-containing joint cavity.

B. Functional classification is based on the amount of movement allowed at the joint (p. 249).

1. Synarthroses are immovable joints.

2. Amphiarthroses are slightly movable joints.

3. Diarthroses are freely movable joints.

II. Fibrous Joints (pp. 249–250; Fig. 8.1; Tables 8.1–8.2)

A. Sutures occur between bones of the skull and use very short connective tissue fibers to hold the bones together (p. 249; Fig. 8.1).

B. In syndesmoses, the bones are connected by a ligament, which is a cord or band of fibrous tissue (pp. 249–250; Fig. 8.1).

C. A gomphosis is a peg-in-socket fibrous joint (p. 250; Fig. 8.1).

A. Synchondroses involve a bar or plate of hyaline cartilage uniting the bones, such as the epiphyseal plate (pp. 250–251; Fig. 8.2).

B. In symphyses, such as the pubic symphysis, the articular surfaces are covered with articular cartilage that is then fused to an intervening pad or plate of fibrocartilage (p. 251; Fig. 8.2).

IV. Synovial Joints (pp. 251–269; Figs. 8.3–8.8, 8.10–8.13; Tables 8.1–8.2)

A. The general structure of a synovial joint contains five distinguishing features (pp. 251–252; Fig. 8.3).

1. Articular cartilage covers the ends of the articulating bones.

2. The joint (synovial) cavity is a space that is filled with synovial fluid.

3. The two-layered articular capsule encloses the joint cavity.

4. Synovial fluid is a viscous, slippery fluid that fills all free space within the joint cavity.

5. Reinforcing ligaments cross synovial joints to strengthen the joint.

B. Bursae and tendon sheaths are bags of lubricant that reduce friction at synovial joints (p. 252; Fig. 8.4).

C. Factors Influencing the Stability of Synovial Joints (pp. 252–254)

1. The shapes of the articular surfaces of bones found at a synovial joint determine the movements that occur at the joint, but play a minimal role in stabilizing the joint.

2. Ligaments at a synovial joint prevent excessive or unwanted movements and help to stabilize the joint; the greater the number of ligaments at the joint, the greater the stability.

3. Muscle tone keeps tendons crossing joints taut, which is the most important factor stabilizing joints.

D. Movements Allowed by Synovial Joints (pp. 254–259; Figs. 8.5–8.6; Table 8.2)

1. In gliding movements one flat, or nearly flat, bone surface glides or slips over another.

2. Angular movements increase or decrease the angle between two bones.

a. Flexion decreases the angle of the joint and brings the articulating bones closer together.

b. Extension increases the angle between the articulating bones.

c. Dorsiflexion decreases the angle between the top of the foot (dorsal surface) and the anterior surface of the tibia.

d. Plantar flexion decreases the angle between the sole of the foot (plantar surface) and the posterior side of the tibia.

e. Abduction is the movement of a limb (or fingers) away from the midline body (or of the hand).

f. Adduction is the movement of a limb (or fingers) toward the midline of the body (or the hand).

g. Circumduction is moving a limb so that it describes a cone in the air.

3. Rotation is the turning of a bone along its own long axis.

4. Special Movements

a. Supination is rotating the forearm laterally so that the palm faces anteriorly or superiorly.

b. Pronation is rotating the arm medially so that the palm faces posteriorly or inferiorly.

c. Inversion turns the sole of the foot so that it faces medially.

d. Eversion turns the sole of the foot so that it faces laterally.

e. Protraction moves the mandible anteriorly, juts the jaw forward.

f. Retraction returns the mandible to its original position.

g. Elevation means lifting a body part superiorly.

h. Depression means to move an elevated body part inferiorly.

i. Opposition occurs when you touch your thumb to the fingers on the same hand.

E. Types of Synovial Joints (p. 259; Fig. 8.7; Table 8.2)

1. Plane joints have flat articular surfaces and allow gliding and transitional movements.

2. Hinge joints consist of a cylindrical projection that nests in a trough-shaped structure, and allow movement along a single plane.

3. Pivot joints consist of a rounded structure that protrudes into a sleeve or ring, and allow uniaxial rotation of a bone around the long axis.

4. Condyloid, or ellipsoid, joints consist of an oval articular surface that nests in a complementary depression, and permit all angular movements.

5. Saddle joints consist of each articular surface bearing complementary concave and convex areas, and allow more freedom of movement than condyloid joints.

6. Ball-and-socket joints consist of a spherical or hemispherical structure that articulates with a cuplike structure. They are the most freely moving joints and allow multiaxial movements.

F. Selected Synovial Joints (pp. 259–269; Figs. 8.8, 8.10–8.13)

1. Knee Joint

a. Enclosed in one joint cavity, the knee joint is actually three joints in one: the femoropatellar joint, the lateral and medial joints between the femoral condyles, and the menisci of the tibia, known collectively as the tibiofemoral joint.

b. Many different types of ligaments stabilize and strengthen the capsule of the knee joint.

c. The knee capsule is reinforced by muscle tendons such as the strong tendons of the quadriceps muscles and the tendon of the semimembranosus.

2. Elbow Joint

a. The elbow joint provides a stable and smoothly operating hinge joint that allows flexion and extension only.

b. The ligaments involved in providing stability to the elbow joint are the anular ligament, the ulnar collateral ligament, and the radial collateral ligament.

c. Tendons of several arm muscles, the biceps and the triceps, also provide additional stability by crossing the elbow joint.

3. Shoulder (Glenohumeral) Joint

a. Stability has been sacrificed to provide the most freely moving joint in the body.

b. The ligaments that help to reinforce the shoulder joint are the coracohumeral ligament and the three glenohumeral ligaments.

c. The tendons that cross the shoulder joint and provide the most stabilizing effect on the joint are the tendon of the long head of the biceps brachii and the four tendons that make up the rotator cuff.

4. Hip (Coxal) Joint

a. The hip joint is a ball-and-socket joint that provides a good range of motion.

b. Several strong ligaments reinforce the capsule of the hip joint.

c. The muscle tendons that cross the joint contribute to the stability and strength of the joint, but the majority of the stability of the hip joint is due to the deep socket of the acetabulum and the ligaments.

5. Temporomandibular Joint

a. The temporomandibular joint allows both hingelike movement and side-to-side lateral excursion.

b. The joint contains an articular disc that divides the synovial cavity into compartments that support each type of movement.

c. The lateral aspect of the fibrous capsule contains a lateral ligament that reinforces the joint.

V. Homeostatic Imbalances of Joints (pp. 269–271; Figs. 8.9, 8.14–8.15)

A. Common Joint Injuries (pp. 269–270; Figs. 8.9, 8.14)

1. Sprains occur when the ligaments reinforcing a joint are stretched or torn.

2. Cartilage tears often occur at the knee, when a meniscus is subjected to compression and shear stress at the same time.

3. Dislocations occur when the bones are forced out of alignment.

B. Inflammatory and Degenerative Conditions (pp. 270–271; Fig. 8.15)

1. Bursitis, an inflammation of the bursa, is usually caused by a blow or friction; tendonitis is inflammation of the tendons, and is usually caused by overuse.

2. Arthritis describes many inflammatory or degenerative diseases that damage the joints, resulting in pain, stiffness, and swelling of the joint.

a. Osteoarthritis is the most common chronic arthritis. It is the result of breakdown of articular cartilage and subsequent thickening of bone tissue, which may restrict joint movement.

b. Rheumatoid arthritis is a chronic inflammatory disorder that is an autoimmune disease.

c. Gouty arthritis results when uric acid is deposited in the soft tissues of the joints.

d. Lyme disease is an inflammatory condition caused by a type of spirochete bacteria transmitted by the bites of ticks living on deer and mice.

A. Joints develop at the same time as bones, resembling adult form by eight weeks gestation (p. 272).

B. At late middle age and beyond, ligaments and tendons shorten and weaken, intervertebral discs become more likely to herniate, and there is onset of osteoarthritis (p. 272).

Laboratory Correlations

1. Marieb, E. N., and S. J. Mitchell. Human Anatomy & Physiology Laboratory Manual: Main Version. Eighth Edition Update. Benjamin Cummings, 2009.

Exercise 13: Articulations and Body Movements

Online Resources for Students

myA&P™

www.myaandp.com

Memory Game: Synovial Joint Movements

Memory Game: Types of Joints

Section 8.5 Homeostatic Imbalances of Joints (pp. 269–271)

Case Study: Articulations

Case Study: Craniosynotosis

Section 8.6 Developmental Aspects of Joints (p. 272)

Chapter Summary

Crossword Puzzle 8.1

Crossword Puzzle 8.2

Web Links

Art Labeling Quiz

Matching Quiz

Multiple-Choice Quiz

True-False Quiz

Chapter Practice Test

Study Tools

Histology Atlas

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Flashcards

8. Joints are defined as sites where two or more bones meet. (p. 248)

9. Freely movable joints provide mobility; slightly movable joints provide strength with limited flexibility; immovable joints provide strong support, secure enclosures, and protection. (p. 249)

10. Bursae are synovial membrane-lined sacs that function to prevent friction, and are located where ligaments, muscles, skin, and/or muscle tendons overlie and rub against bone. In the latter case, the friction-reducing structures are called tendon sheaths. (p. 252)

11. Nonaxial movements mean slipping movements only, uniaxial movements mean movement in one plane, biaxial movements mean movement in two planes, and multiaxial movements mean movement in or around all three planes and axes. (p. 253)

12. Flexion and extension refer to decreasing or increasing the angle of a joint and bringing the two articulating bones together along the sagittal plane, while adduction and abduction refer to moving a limb closer to or away from the body midline along the frontal plane. (p. 255)

13. Rotation means to turn a bone around its own long axis, while circumduction means to move a limb so that it describes a cone in space, an action that involves a variety of movements. (p. 256)

14. Uniaxial—hinge (elbow) and pivot (atlantoaxial and radioulnar); biaxial—condyloid (knuckle) and saddle (thumb); multiaxial—ball and socket (shoulder and hip). (p. 259)

15. The knee menisci deepen the articulating surface of the tibia to prevent side-to-side rocking of the femur on the tibia and to absorb shock transmitted to the knee joint. The cruciate ligaments prevent anterior/posterior displacement of the articulating bone and help to secure the joint. (pp. 262–264)

16. The knees must carry the total body weight and rely heavily on nonarticular factors for stability. The knees can absorb an upward force of great intensity; although they must also absorb direct blows and blows from the side, they are poorly designed to do so. (p. 262)

17. Cartilages and ligaments are poorly vascularized and tend to heal very slowly. (p. 264)

18. The fibrous capsule, composed of dense irregular connective tissue, is the external layer of the articular (joint) capsule, and strengthens the joint so that the bones are not pulled apart. Synovial fluid occupies all free spaces within the joint capsule, including that within the articular cartilages, and serves to reduce friction between the cartilages. Synovial fluid also contains phagocyctic cells that rid the joint cavity of microbes or cellular debris. Articular cartilage is glassy-smooth hyaline cartilage that covers the opposing bone surfaces. These thin, spongy cushions absorb compression placed on the joint, keeping bone ends from being crushed. (p. 251)

1. Most likely bursitis of the subcutaneous prepatellar bursa. It is a good guess that Sophie spends a good deal of time on her knees (perhaps scrubbing the floors). (p. 270)

2. a. Not really. The shape of the articular surfaces is not as enclosed as other joints, and has a greater degree of flexibility due to the fact that three bones, not two, create the joint. Also, there are relatively few strong muscles and ligaments that cross this joint, compared to other joints, such as the hip or knee. (p. 262)

b. Ligaments, which tie the bones to each other. (p. 262)

c. Returning bones back to position without an incision. (p. 270)

d. Sprains heal slowly and need repair to stabilize joint. (p. 270)

e. The examination of a joint by means of an endoscope. (p. 269)

f. Using arthroscopic surgery, only small incisions are needed instead of an open surgical wound. There is less chance of infection and healing is considerably faster. (p. 269)

3. a. Probably gout, although it is more common in males.

b. Caused by a deposition of uric acid crystals in soft tissues of joints. (p. 271)