Which of the following statements are true regarding the human throat? S1. The windpipe runs adjacent to the foodpipe in the throat. S2. A flap-like valve (epiglottis) is present in the throat. S3. Air and food share a common passage in the throat. S4. Sometimes food particles enter the windpipe, which may cause hiccups.

Which of the following organs is the longest part of the alimentary canal in humans?

The thinnest blood vessels in the human circulatory system, which are only one-cell thick, are called:

Which of the following statements regarding urine composition and micturition in a normal human is correct? A. Normal urine is slightly acidic (average pH ~6), though diet can shift it between 4.5 and 8. B. Daily urea excretion via urine is about 25 to 30 g. C. Presence of ketone bodies in urine indicates abnormal metabolism, commonly seen in uncontrolled diabetes mellitus. D. Micturition involves contraction of bladder smooth muscle (detrusor) and relaxation of urethral sphincter.