The structural and functional unit of the thyroid gland is the

Correct Answer: A

Rationale: The thyroid gland's functional unit is the follicle, where thyroid hormones are synthesized and stored. 'Follicle,' is correct, per histology texts like Ross and Pawlina, consisting of follicular cells around colloid. 'Acini,' are exocrine gland units (e.g., pancreas). 'Islets of Langerhans,' are pancreatic endocrine units. 'Alveoli,' are lung units. Follicles' role in T3/T4 production distinguishes A as the accurate answer, specific to thyroid anatomy.

Correct Answer: D

Rationale: Micturition (urination) is regulated by the autonomic nervous system, with parasympathetic and sympathetic inputs, though somatic control aids voluntary aspects. 'Autonomic,' is correct, per physiology (e.g., Tortora), coordinating bladder contraction (parasympathetic) and inhibition (sympathetic). 'Somatic,' controls external sphincter voluntarily, not the full process. 'Parasympathetic,' is partial, not whole. 'Sympathetic,' inhibits, not controls alone. Autonomic's overarching role makes D the precise answer.

Correct Answer: B

Rationale: Tidal volume is the air moved in a normal breath, about 500 ml. 'Tidal volume,' is correct, per respiratory physiology (e.g., Guyton). 'Vital capacity,' is maximum breathable volume. 'Residual volume,' remains after exhalation. 'Inspiratory reserve volume,' is extra inspiratory capacity. Tidal volume's resting measure makes B the accurate answer.

Correct Answer: C

Rationale: Connective tissues support and connect, with diverse forms. 'Muscle,' is correct as the exception, a contractile tissue, per histology (e.g., Ross). 'Bone,' and 'Cartilage,' are skeletal connective tissues. 'Blood,' is fluid connective tissue. Muscle's distinct function distinguishes C as the accurate answer.

Correct Answer: C

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.