Which curve of the spine is formed when a child begins to walk?

Correct Answer: C

Rationale: The lumbar curve, a secondary curvature, forms when a child walks, shifting weight to an upright posture, enhancing balance. Cervical forms earlier (head lifting). Thoracic and sacral are primary, fetal curves. Lumbar's development, per spinal ontogeny, makes 'c' correct.

Correct Answer: C

Rationale: Regional anatomy studies all structures (bones, muscles, nerves, etc.) within a specific body area, like the ankle and foot, making it ideal for a comprehensive focus on that region's anatomy. Microscopic anatomy examines cells/tissues at a cellular level, not gross structures. Muscle anatomy is too narrow, focusing only on muscles, not all ankle/foot components. Systemic anatomy studies body systems (e.g., skeletal) across the whole body, not one region. Regional anatomy's localized, all-inclusive approach, per anatomical study methods, makes 'c' the correct specialty.

Correct Answer: C

Rationale: In cold, the body breaks down stored energy (e.g., glycogen, fat) via metabolism to generate heat (thermogenesis), maintaining core temperature. Blood to hands/feet decreases (vasoconstriction) to save heat. Lethargy isn't primary shivering is. Blood oxygen doesn't spike, it's steady. Energy breakdown, per thermoregulation, makes 'c' correct.

Correct Answer: C

Rationale: Ultrasounds use sound waves, safe for pregnancy, avoiding radiation risks to the fetus, commonly monitoring development. CT and X-rays emit ionizing radiation, harmful. PET uses radioactive tracers, also risky. Ultrasound's non-invasive safety, per medical practice, makes 'c' correct.

Correct Answer: A

Rationale: Slow, oxidative skeletal muscle fibers (Type I) excel in endurance, resisting fatigue due to high mitochondrial density and oxidative enzyme activity, relying on aerobic metabolism. Their red color stems from abundant myoglobin, an oxygen-storing protein, and rich capillary networks, supporting sustained activity like posture maintenance or marathon running. Fast fibers (Type II), white or pale, depend on glycolysis, fatiguing quickly in bursts like sprinting. Pink fibers, an intermediate type (Type IIa), blend traits but aren't slow or maximally enduring. Histochemical staining reveals Type I's oxidative capacity up to 50% more mitochondria than fast fibers and their myoglobin content, absorbing red light. White fibers, low in myoglobin, fatigue rapidly under anaerobic conditions. Red fast fibers exist but prioritize speed over endurance. Exercise science links these traits to function: slow fibers' fatigue resistance suits long-term effort, contrasting with fast fibers' power, making their slow, red profile distinct in muscle classification.