Which fracture is characterized by a bone breaking through the skin?

Correct Answer: B

Rationale: A compound (open) fracture breaks through the skin, exposing bone, risking infection (e.g., tibia piercing). Simple stays internal. Stress is microdamage from overuse. Greenstick bends, common in kids. Compound's external breach, per trauma classification, makes 'b' correct.

Correct Answer: B

Rationale: The knee joint, or femorotibial joint, is between the femur and tibia, a hinge for leg movement. Humeroulnar is elbow, coxofemoral is hip, talocrural is ankle. Femorotibial's specificity, per joint nomenclature, makes 'b' correct.

Correct Answer: A

Rationale: An organ, like the stomach, is a collection of similar tissues (e.g., muscle, epithelium) working together for a specific function (digestion). An organelle is a cellular structure (e.g., mitochondria), not tissues. An organism is the whole living entity. An organ system like the digestive system includes multiple organs, broader than one. The organ's tissue-based, functional unity, per anatomical hierarchy, makes 'a' correct.

Correct Answer: B

Rationale: Childbirth uses a positive feedback loop: uterine contractions increase oxytocin, intensifying contractions until delivery, amplifying the stimulus. Blood pressure , fluid balance , and temperature use negative feedback to stabilize. Positive feedback's escalating nature in labor, per physiology, makes 'b' correct.

Correct Answer: A

Rationale: Smooth muscle, found in visceral organs like the stomach and blood vessels, lacks striations due to its unorganized actin and myosin arrangement, unlike the sarcomeres of skeletal and cardiac muscle. It operates involuntarily, controlled by the autonomic nervous system, enabling functions like peristalsis without conscious effort. Skeletal muscle, attached to bones, is striated and voluntary, governed by the somatic nervous system for deliberate movements. Cardiac muscle, in the heart, is striated with intercalated discs and involuntary, but its rhythmic contractions distinguish it from smooth muscle's slower, sustained actions. Visceral typically denotes internal organs, aligning with smooth muscle's role, not cardiac or skeletal. Histologically, smooth muscle's spindle-shaped, uninucleate cells contrast with skeletal's multinucleate fibers and cardiac's branched structure. Physiological texts emphasize smooth muscle's unique calcium regulation via calmodulin, not troponin, reinforcing its distinct involuntary nature. This specificity clarifies why only smooth muscle fits all three descriptors, avoiding overlap with striated types.