rmxyz, you left your joke incomplete...Lemme complete the 2nd part:

Lecturer in a medical college class: Man's semen contains glucose.

One of the female students had doubt and she asks: Then why it
doesn't taste sweet?

The professor replies, "Because your tase buds are located on the tip of your tongue, not at the back of your throat".  After this, the red-faced student runs outta the class too ashamed to utter a word!!