An 80-year-old man falls and suffers a compound fracture of the femur. The most appropriate immediate action is to:

Correct Answer: C

Rationale: A compound fracture, with bone piercing skin, risks bleeding and infection, so the immediate action is stabilizing it. Splinting the leg as it lies immobilizes the fracture, minimizing further damage, blood loss, and pain until medical help arrives. Lying flat might worsen alignment or bleeding without stabilization. A tourniquet is extreme, used only for uncontrolled hemorrhage, not standard here. Straightening the leg risks worsening the injury, driving bone deeper or increasing bleeding. Splinting preserves the current state, aligning with first-aid principles for open fractures, ensuring safety and reducing complications before transport.

Correct Answer: D

Rationale: In a lever system, motion occurs when the effort (muscle contraction force) at the insertion exceeds the load (resistance), causing the movable bone to shift. For example, in a bicep curl, the biceps' effort at the radius (insertion) must overcome the weight to flex the elbow. If resistance at the insertion exceeds the load, it implies no motion, as the load wins. If the force is less than the load, no movement happens. Effort at the origin (stationary point) doesn't directly cause motion. Effort at the insertion exceeding the load is the correct biomechanical condition for lever movement, making it the right answer, reflecting how muscles drive skeletal levers.

Correct Answer: B

Rationale: Strabismus is the condition of misaligned eyes (crossed eyes), where eye muscles fail to coordinate, common in young children and treatable with therapy or surgery. The child recognizing people suggests vision is intact, just misaligned. Nystagmus is involuntary eye movement, not crossing. Presbyopia is age-related focus loss, irrelevant here. Myopia is nearsightedness, not alignment-related. Strabismus matches the crossed-eye presentation, making it the correct answer, as it's a muscle coordination issue distinct from refractive or movement disorders, often seen in pediatric cases.

Correct Answer: C

Rationale: Nodding yes involves extension (head tilts back) and flexion (head tilts forward) at the neck, driven by muscles like the sternocleidomastoid and splenius. Rotation and circumduction involve turning or circling, not nodding. Lateral/medial rotation twists the head, not tilting it. Abduction/adduction don't apply to neck nodding. Extension and flexion are the correct actions, as they describe the up-and-down motion, fundamental to neck kinematics in this gesture.

Correct Answer: C

Rationale: The human body contains approximately 640 muscles, a widely accepted estimate in anatomy reflecting skeletal muscles primarily, which vary slightly by individual due to small accessory muscles. This number excludes smooth and cardiac muscles' microscopic units but focuses on distinct, named skeletal muscles enabling movement. Fewer, like 340, undercounts the extensive network across limbs, torso, and face. Higher figures like 860 might exaggerate by including minor variants or non-skeletal types, but 640 aligns with standard texts. It accounts for paired muscles (e.g., biceps) and smaller ones (e.g., in the ear), balancing precision with practicality. This figure underscores the muscular system's complexity, supporting diverse functions from walking to facial expressions, and provides a reliable benchmark for anatomical study, distinguishing it from overly broad or narrow estimates.