9.9: Applied Thinking Self‑Check

Challenge Yourself

• Purpose: Show how joint structure explains joint movement and stability.
• How to answer (per question):
  1. Direct answer: one sentence that clearly answers the main prompt.
  2. Mechanism: 3 to 5 sentences that explain how structure (bones, cartilage, ligaments, capsule, muscles) creates the function (movement/stability). Use cause → effect language.
  3. Example or small diagram: 1 to 2 sentences (or a simple labeled sketch) that supports your claim.

1. Define how joints are classified based on function. Describe and give an example for each functional type of joint.
2. The periodontal ligaments are made of collagen fibers and are responsible for connecting the roots of the teeth to the jaws. Describe how scurvy, a disease that inhibits collagen production, can affect the teeth.
3. A student reports jaw clicking and brief “lock” when chewing gum. Explain how the temporomandibular joint (a modified hinge with an articular disc) can cause these symptoms. Include the role of the disc, the joint’s gliding + hinge motions, and muscle tension. Suggest one self-care change (e.g., softer diet, limiting gum) and the mechanism for relief.
4. Which joint is more mobile and which is more stable: the shoulder (glenohumeral) or the hip? Explain how their structures (socket depth, labrum, capsule tightness, surrounding ligaments, muscle support) create these differences. Give one common injury risk for each joint and one strategy to protect it in daily life.
5. Explain how the knee becomes stable in full extension (“locks”) and how it “unlocks” to start flexion. Then predict what movement or activity becomes harder or riskier if the anterior cruciate ligament (ACL) is torn, and why. Include the role of rolling-gliding and one stabilizer (e.g., menisci, collateral ligaments, capsule).
6. The elbow does two main things: hinge flexion/extension and forearm pronation/supination. Name the joints that do each movement (humeroulnar/humeroradial vs proximal radioulnar) and explain how their shapes (hinge vs pivot) allow these actions. Give one everyday task for each movement (e.g., lifting a cup vs turning a doorknob) and link it to the joint.
7. Compare the pubic symphysis (fibrocartilage, limited movement) with the knee (synovial, hinge with menisci). How does each joint’s tissue and design match its function in walking and load-bearing? Predict one problem that occurs if the meniscus is torn or if the pubic symphysis becomes too mobile, and explain why.