Select the one INCORRECT statement about skeletal muscles

Correct Answer: A

Rationale: An agonist drives movement (e.g., biceps in flexion), not opposes antagonists (e.g., triceps) do. Origin is the fixed attachment, skeletal cells are syncytial (multinucleate), and fixators stabilize. The agonist's role as prime mover distinguishes the error, key to movement dynamics.

Correct Answer: C

Rationale: A convergent fascicle pattern features fibers converging from a broad origin to a narrow insertion, like a fan, maximizing force direction versatility, as in the pectoralis major, which spans the chest to insert on the humerus. Biceps brachii has parallel fascicles along its length. Gluteus maximus is multipennate, with angled fibers for power. Rectus femoris has a bipennate structure, not convergent. Pectoralis major's triangular, convergent design, enabling shoulder adduction and flexion, matches this pattern, making 'c' correct.

Correct Answer: C

Rationale: The erector spinae, a muscle group along the spine (e.g., iliocostalis, longissimus), provides postural support, extending the back to maintain upright stance against gravity. Arm movement involves deltoid or latissimus dorsi. Pelvic stabilization is more gluteal or abdominal. Rotation involves obliques or rotatores, not primarily erector spinae, which focuses on extension. Its role in posture, critical for standing/sitting, makes 'c' the correct function.

Correct Answer: B

Rationale: The gastrocnemius, a two-headed muscle overlying soleus, is the largest in the lower leg, spanning from femoral condyles to the Achilles tendon, driving plantarflexion (e.g., calf raises). Soleus , beneath it, is smaller but assists. Tibialis anterior dorsiflexes, and tibialis posterior inverts both are slimmer. Gastrocnemius's bulk and superficial prominence, critical for locomotion, make 'b' the correct answer.

Correct Answer: B

Rationale: The body of a cervical vertebra (C3-C7) is oval-shaped when viewed superiorly, wider side-to-side than front-to-back, supporting the neck's weight and mobility. Round doesn't fit cervical bodies aren't circular. Heart-shaped applies more to sacral vertebrae in some contexts, not cervical. Triangular describes vertebral foramina, not bodies. The oval shape, seen in anatomical diagrams, optimizes load distribution and flexibility, making 'b' the correct description.