Short Answer Essay Questions Joints are defined as sites where two or more bones meet. (p. 249) 9

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Ch 8 Answers to End-of-Chapter Questions

Multiple-Choice and Matching Question answers appear in Appendix H of the main text.

Short Answer Essay Questions

8. Joints are defined as sites where two or more bones meet. (p. 249)

9. Freely movable joints provide mobility; slightly movable joints provide strength with limited flexibility; immovable joints provide strong support, secure enclosures, and
protection. (p. 250)

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. 253)

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 or axes. (p. 256)

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. 258)

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. 258)

14. Uniaxial joints include hinge (elbow) and pivot (atlantoaxial and radioulnar) joints;
biaxial joints include condylar (knuckle) and saddle (thumb) joints; multiaxial joints
include ball-and-socket (shoulder and hip) joints. (pp. 254–255; Table 8.2)

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. 263–264)

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. Knees are poorly designed to do the latter. (p. 263)

17. Sprains and cartilage injuries are particularly problematic because cartilage and ligaments are poorly vascularized and tend to heal very slowly. (p. 264)

18. The fibrous layer, composed of dense irregular connective tissue, is the external layer of the articular capsule and strengthens the joint so that the bones are not pulled apart. Synovial fluid occupies all free spaces within the articular capsule, including that within the articular cartilages, and serves to reduce friction between the cartilages. Synovial fluid also contains phagocytic 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. 252)

Critical Thinking and Clinical Application Questions

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. 253)

2. a. The ankle joint is not really a stable joint. 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. 255)

b. Joint stability depends on ligaments, which tie the bones to each other. (p. 252)

c. A closed reduction involves returning bones back to position without an incision.
(p. 270)

d. Ligament repair is necessary because ligaments heal too slowly on their own, and joint stabilization needs to be done soon after injury for optimal healing. (p. 269)

e. Arthroscopy is 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. Mrs. Bell’s arthritis is probably due to gout, although gout is more common in males.

b. Arthritis due to gout is caused by a deposition of uric acid crystals in soft tissues of joints. (p. 270)

4. The vector for the bacteria that causes Lyme disease is the deer tick, a very small tick carried by deer and other small mammals. (p. 270)

5. When Tony’s mouth opened very wide, the mandibular condyle slid forward to the point that the joint dislocated. (p. 269)

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