Which of the following contributes maximum to the buffer capacity of human body?
1. carbonic acid/bicarbonate buffer system.
2. phosphate buffer system.
3. protein buffer system.
4. oxygen/carbondioxide buffer system.

Assertion: Penicillin should be administered in large doses and several times per day.
Reason: Penicillin is eliminated in the urine by very rapid secretion in the tubules.

1. Both assertion and reason are true and the reason is the correct explanation of the assertion.
2. Both assertion and reason are true but the reason is not the correct explanation of the assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

Regarding the reabsorption of bicarbonate ions in the proximal convoluted tubule, the correct statement is:
1. The cuboidal brush bordered epithelium directly reabsorb bicarbonate ions.
2. The cells secrete H⁺ ions to reabsorb all of the filtered bicarbonate.
3. Carbonic anhydrase is not found in the PCT.
4. More bicarbonate is reabsorbed and less bicarbonate is excreted in alkalosis.

What would be the logical consequence of an increased hydrogen ion concentration of the ECF?
1. An increase in ECF pH.
2. A slower respiratory rate.
3. An increase in urinary pH.
4. An increase in hydrogen ion secretion by kidney.

A triangular portion of the bladder floor bordered (ventrally) by the internal urethral opening or bladder neck and (dorsolaterally) by the orifices of the right ureter and left ureter, is called as:

1. detrusor.

2. dartos.

3. transitional epithelium.

4. trigone.