Which of the following muscles is responsible for smiling?
Buccinator
Zygomaticus
Mentalis
Orbicularis oris
Masseter
The Correct Answer is B
Choice A reason: The buccinator muscle compresses the cheek, aiding in actions like blowing and chewing. While it contributes to facial expression, it is not the primary muscle responsible for smiling.
Choice B reason: The zygomaticus muscle is the correct answer. It originates from the zygomatic bone and inserts into the corner of the mouth. Its contraction pulls the mouth upward and outward, producing a smile. It is the principal muscle involved in smiling.
Choice C reason: The mentalis muscle elevates and wrinkles the skin of the chin and protrudes the lower lip. It is involved in expressions of doubt or displeasure, not smiling.
Choice D reason: The orbicularis oris encircles the mouth and controls movements of the lips, such as puckering or closing. It is essential for speech and kissing but not for smiling.
Choice E reason: The masseter is a major muscle of mastication (chewing). It elevates the mandible to close the jaw and has no role in facial expressions like smiling.
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Naxlex Comprehensive Predictor Exams
Related Questions
Correct Answer is E
Explanation
Choice A reason: Central lamellae is not a recognized anatomical term. The central canal, however, is part of an osteon and contains blood vessels and nerves. It does not refer to lamellae between osteons.
Choice B reason: Concentric lamellae are rings of bone matrix that surround the central canal within an osteon. They are integral to the osteon structure and not found between osteons.
Choice C reason: Circumferential lamellae are located around the outer and inner surfaces of compact bone, encircling the entire bone structure. They are not found between osteons.
Choice D reason: Perforating canals, or Volkmann’s canals, run perpendicular to the central canals and connect them to the periosteum and medullary cavity. They are not lamellae and do not lie between osteons.
Choice E reason: Interstitial lamellae are remnants of old osteons that have been partially resorbed during bone remodeling. They fill the spaces between current osteons and are not part of any single osteon, making them the correct answer.
Correct Answer is D
Explanation
Choice A reason: "Osseosus" is not a recognized scientific law or principle. It appears to be a misspelling or fictional term.
Choice B reason: Dalton's Law pertains to the behavior of gases, specifically the partial pressures in a mixture. It has no relevance to bone remodeling.
Choice C reason: "Calcine's" is not a known law or principle in physiology or anatomy. It may be a misrepresentation or confusion with calcitonin, a hormone involved in calcium regulation.
Choice D reason: This is correct. Wolff's Law states that bone grows and remodels in response to the mechanical stresses placed upon it. This principle explains how bones adapt to increased load or disuse by altering their density and structure.
Choice E reason: Boyle's Law relates to the pressure and volume of gases in a closed system. It is unrelated to bone physiology.
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