Human Females Menstruate to Eliminate Unviable Fetuses

From a female perspective, pregnancy is always a huge investment. Even more so if her species has a hemochorial placenta. Once that placenta is in place, she not only loses full control of her own hormones, she also risks hemorrhage when it comes out. So it makes sense that females want to screen embryos very, very carefully. Going through pregnancy with a weak, inviable or even sub-par fetus isn't worth it. That's where the endometrium comes in. You've probably read about how the endometriu...

 Gamification Pickup and Deliver Mechanic

Dr. Boxer decides to create a game board that depicts a cell and pieces for 12 different materials that might be transported into or out of the cell. Students are assigned to teams and given the opportunity to place certain materials either in the cell or in the bloodstream (which surrounds the cell and through which these materials move around the board). He then adds a small role-playing element to the game by giving each team an identity (such as a moving company) and an objective separate...

 The Chemical Decline in Energy

It is the destiny of wine to be drunk, and it is the destiny of glucose to be oxidized. But it was not oxidized immediately: its drinker kept it in his liver for more than a week, well curled up and tranquil, as a reserve aliment for a sudden effort; an effort that he was forced to make the following Sunday, pursuing a bolting horse. Farewell to the hexagonal structure: in the space of a few instants the skein was unwound and became glucose again, and this was dragged by the bloodstream all t...