An increase in the permeability of the cells of the collecting tubule to water is due to a(n)

A. Impermeability of the collecting tubule to water: In the absence of ADH, the collecting duct is impermeable to water, allowing dilute urine to be excreted.
B. The presence of ADH: ADH increases water reabsorption, leading to concentrated urine, not dilute.
C. Relative permeability of the distal tubule to water: If the tubule is permeable to water (due to ADH), water is reabsorbed, and urine becomes concentrated.
D. Transport of sodium and chloride ions out of the descending nephron loop: The descending limb is not permeable to salts-only the ascending limb actively reabsorbs Na⁺ and Cl⁻.

A. The voluntary phase of swallowing takes place within the mouth: The oral phase is under voluntary control and involves tongue movement to push the bolus to the oropharynx.
B. The epiglottis assists in propelling food into the trachea: This is incorrect. The epiglottis prevents food from entering the trachea by covering the glottis during swallowing; it does not propel food.
C. The involuntary portion of swallowing takes place in the pharynx: After the oral phase, swallowing becomes involuntary, involving reflexive contractions of pharyngeal muscles.
D. The mouth, pharynx and esophagus all take part in swallowing: All three structures are involved in the three phases of deglutition: oral, pharyngeal, and esophageal.