Monday, April 16, 2007

More Female Anatomy and PBL

We continued with female anatomy today. One of the cadavers had her feet tied up like she was having a Pap smear done. This was to show us the external female genitalia. That station actually wound up being pretty interesting because the resident was showing us how to do pelvic exams. One of the pearls of wisdom she gave us was that we should never touch the woman's clitoris or urethra when inserting a speculum into the woman's vagina. Well, that is good information to know I suppose, although I really hope that giving tons of pelvic exams is not in my future.

The other cadavers were dissections of the internal genitalia and the nerves and blood vessels. There were only four groups today, so there were more of us in each group than normal. That would have been annoying, but the cadaver for the blood vessels and nerves smelled so strongly that I didn't have any trouble getting up to the front for as much of a look as I wanted. Plus, I went back later in the afternoon for office hours and went through both cadavers a second time. Lately no one else has been coming to office hours while I'm there, so one of the anatomy profs goes through all of the cadavers with me one on one.

Our new PBL case is a good one. I'm pretty sure that we already know what's wrong with the patient, although our tutor kept asking how we were so sure. This case has a lot of anatomy and embryology in it, so I volunteered to do the embryology learning objective for Wednesday. It's actually really interesting, which is not my normal feeling about embryology. All fetuses start out undifferentiated, meaning that they aren't obviously male or female. If they have a Y-chromosome, they start to develop into males, but it takes a couple of months for that to happen. The default sex for humans is female though. So if something goes wrong with a fetus's development, a boy could come out looking like a girl even if he's genetically a boy, or vice versa.

Interestingly, in other species (like birds), the opposite is true. They are males by default. And, unlike humans, they don't have X and Y sex chromosomes. Instead, male birds are ZZ and females are ZW. And then in some animals like turtles, sex determination for an embryo depends on environmental factors like where in the nest the egg is. The hottest eggs near the top become the females, while the eggs in the cooler part of the nest become the males. In alligators, the hotter eggs become males. Weird stuff, completely useless to know, and nonetheless fascinating.

No comments: