Anatomy chapter 9 SHORT ANSWER
A high school student comes to the emergency room complaining of persistent pain and stiffness in her shoulder joint. In talking with her, you discover that she has been spending many hours trying to improve her pitching skills for her school's softball team. What is likely causing the pain?
Her pain is probably caused by injury to the rotator cuff, which can result from repetitive motion, trauma, or excessive force. The rotator cuff consists of the tendons of four muscles that stabilize the shoulder joint. If torn, surgical repair may be indicated.
How are osteoarthritis and rheumatoid arthritis different?
Osteoarthritis is a "wear-and-tear" disease seen usually in the elderly. Rheumatoid arthritis is an autoimmune disease in which the body's immune system attacks synovial joints, triggered by an infection or some other cause.
Why is the inferior region of the shoulder joint most vulnerable to dislocation?
The anterior, superior, and posterior surfaces of the shoulder joint are reinforced by ligaments, muscles, and tendons, but the inferior capsule is poorly reinforced. As a result, a dislocation caused by an impact or a violent muscle contraction is most likely to occur at this site. Such a dislocation can tear the inferior capsular wall and the glenoid labrum.
When the triceps brachii muscle contracts, what movements does it produce?
The triceps brachii attaches to the olecranon process. Contraction of the triceps brachii muscle causes the ulna to rotate around the distal humerus, causing extension of the forearm.