Yay sex! Not gonna lie; it was an interesting day. I can't tell if everyone is actually getting more mature or if we've just gotten better at holding back the giggles. Maybe that's all maturity is.
TIL: Sperm are not transported to the site of fertilization by their own means (e.g. their flagellate tail). An inert particle placed at the vaginal opening of the cervix will get to the site of fertilization just as fast as a sperm. The tail is used for smaller distances like getting to the egg once in the general vicinity and for penetrating the egg's membranous defenses.
Calcium intake has to be closely watched during pregnancy. If the mother cannot provide enough calcium from the diet, her body with start breaking down bone to fill the gap.
The placenta is very cancer-like. It grows rapidly, produces hormones in proportion to its own size, and is autologous (unresponsive to all normal feedback loops). It is only stopped by being removed during parturition (the time leading up to and including labor and delivery).
So to recap, pregnancy is like growing a parasite within a bubble of cancer inside your body. Yay!
Physiologists are terrible at drawing breasts. The lactating breast is like a bunch of grapes still connected to the stem. The stems are the lactiferous sinuses and ducts that branch out from the opening of the nipple. The grapes are alveoli that secrete milk and, upon manual stimulation of the areola*, can pump milk into the ducts in preparation for lactation. Suckling by the infant causes the release of the hormone oxytocin which feeds back to the alveoli causing contraction and release of milk. If the baby is not switched between the breasts when feeding, the unused breast can eventually begin leaking milk from over-stimulation by oxytocin.
Babies do not suck milk out of the breast. The ducts have very weak walls that would instantly collapse if placed under negative pressure. Instead a baby pinches the nipple in its mouth and rhythmically squeezes the breast tissue, quite literally milking it. There is probably some sucking going on, but that's not the principle means of excretion.
For some humor on the topic of maturity and breasts, enjoy this song by Tim Minchin (contains some explicit and inappropriate language):
*I had thought that areolus was the singular, but in fact areola is the singular and areolæ is the plural. Learned all sort of things today!
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