Quiz 1 and 2

I posted the scores for quiz 1 on Canvas just now. I added a point to everyone’s score for that question about community-acquired pneumonia that was miskeyed. Please take a look and make sure that your score looks right!

Also – tomorrow we’ll have quiz 2 at the beginning of the hour, and then a short lecture on Upper GI Pathology. Quiz 2 will cover everything we’ve done since quiz 1, which means Respiratory Pathology (slides 46-63) and Renal Pathology.

Let me know if you have any questions!

Quiz 1 coverage

Just a quick note about what quiz 1 will cover.

In class today, we went through most of the Respiratory Pathology lecture (we did slides 1-45) – but we did not talk about lung cancer (slides 46-63).

So on Monday (9/26), we’ll begin with quiz 1, which will cover everything we’ve done so far (all the lectures from 9/7-9/21). Then we’ll finish off the rest of Respiratory Pathology (slides 46-63).

All of this is listed on our lectures page.

Please let me know if you have any questions!

Which direction does blood flow through the ductus arteriosus?

Here’s a great question from last year that helps sort out the issue of which way blood flows through the ductus arteriosus.

Q. I just had a quick question for you. Our notes say that a ductus arteriosus allows flow from the pulmonary artery to the aorta, which I knew. However, they also say that it’s a left to right shunt, and that it can become right to left. This confuses me, since from what I know, flow would be going from right (pulmonary artery) to left (aorta).

A. When we talk about the ductus allowing flow from the pulmonary artery (right) to aorta (left), we’re talking about intrauterine flow through the ductus. Before birth, the pressure on the right side of the heart is greater than the pressure on the left – so blood flows from pulmonary artery to aorta (through the ductus).

After birth, though, the pressure on the left becomes greater than the pressure on the right. In most babies, the ductus closes (probably in response to the new levels of oxygen in the blood). In some babies it remains patent, in which case flow would now be from the aorta (left; higher pressure) to the pulmonary artery (right; lower pressure).

If the ductus is widely patent, then after a while, that left to right shunt can put enough pressure on the lungs that they react by closing down vessels, effectively making it more difficult to push blood through. Now the right heart has to work really hard to push blood through the lungs – and it can get to the point where the right heart is actually bigger and stronger than the left, making the shunt reverse and go from pulmonary artery (right; higher pressure) to aorta (left; lower pressure).