When a 90-year-old patient says, My old bones are just about done in, the nurse reminds him that his bones are being constantly renewed through the action of:

Correct Answer: A

Rationale: Bone renewal is an ongoing process called remodeling, driven by osteoblasts, cells that build new bone by depositing mineralized matrix. This counters the patient's notion of bones wearing out, as osteoblasts work with osteoclasts (which break down bone) to maintain skeletal health, even in old age. Stem cells contribute broadly to tissue repair but aren't specific to bone renewal. Free calcium ions are raw materials, not active agents. Phosphorus and vitamin D support mineralization, but osteoblasts execute the process. Highlighting osteoblasts reassures the patient that regeneration persists, emphasizing the dynamic nature of bone tissue over passive nutrient roles.

Correct Answer: A

Rationale: Buck's traction uses weights and pulleys to align a leg fracture, requiring proper positioning to avoid complications. Heels not touching the mattress suggest the legs are elevated or misaligned, risking pressure on the heels or traction ineffectiveness, necessitating repositioning. Rewrapping bandages addresses maintenance, not position. Feet against the footboard could indicate too much pull, but it's less urgent if traction remains functional. Free-hanging weights are correct for traction. Heels off the bed signal a positional flaw, potentially causing skin breakdown or misalignment, making it the priority for adjustment to ensure therapeutic effect.

Correct Answer: A

Rationale: Synergists are muscles that assist the prime mover by stabilizing joints or reducing unwanted movements, enhancing the efficiency of the intended action. For example, when flexing the elbow, synergist muscles stabilize the wrist to focus the biceps' effort. Antagonist' muscles oppose the prime mover, not assist it. Intramuscular (IM) injection is a medical procedure, not a muscle type. The prime mover is the primary muscle responsible for the action, not an assistant. Synergists play a crucial supportive role in refining movement, making them the correct choice, as they align with the description of reducing unnecessary motion while complementing the prime mover's function.

Correct Answer: A

Rationale: Nodding yes involves flexion, extension, and hyperextension of the neck, with the skull pivoting at the atlanto-occipital joint (fulcrum). This is a first-class lever, where the fulcrum (joint) lies between the effort (neck muscles, like the splenius) and the load (head weight). Like a seesaw, the head rocks forward and back. Second-class levers (e.g., standing on tiptoes) have the load between fulcrum and effort, not applicable here. Third-class levers (e.g., biceps curl) place effort between fulcrum and load, unlike nodding. The first-class lever system matches the neck's motion, making it the correct answer, as it aligns with the anatomical mechanics of head movement at the fulcrum.

Correct Answer: A

Rationale: At the wrist, forearm muscles enable flexion (bending), extension (straightening), abduction (radial deviation), and adduction (ulnar deviation). At the interphalangeal joints of fingers, only flexion and extension occur, as abduction/adduction apply to spreading fingers at metacarpophalangeal joints, not interphalangeal ones. Thus, flexion, extension, abduction, and adduction describe wrist movements but not interphalangeal finger actions, making it the correct answer. Other options omit key wrist motions or include finger-relevant terms, missing the distinction required by the question, which hinges on joint-specific movement capabilities.