Respiratory tree drawings

Thought I’d share a drawing with you guys in case it helps. It shows how the wall of the respiratory passageways changes as you go from bronchi to alveoli. There are three versions, so you can use it fully labeled, partially labeled, or unlabeled, however it suits you best. Let me know if you find it useful – if so, I’ll make more 🙂


Labeled with passageways only:

Fully labeled:



Exam scores are up!

Exam scores are back, finally! I don’t know what the holdup was – but they’re up now.

You guys did REALLY WELL. Here’s some stats, before adding a point (see below):

  • Mean: 46 (out of 49)
  • SD: 2.47
  • High score: 49
  • Low score: 34

All the questions except one performed really well (between 90-100% of the class got them right). The question that gave you guys trouble was this one:

Blood cells leave the marrow, circulate in the blood for a certain period of time, and eventually are removed from the blood. The cells that spend the longest amount of time in the blood are _____, and the cells that are in the blood for the shortest period of time are ______.

A. Platelets; neutrophils
B. Erythrocytes; platelets
C. Neutrophils; erythrocytes
D. Neutrophils; platelets
E. Erythrocytes; neutrophils

The correct answer was E (erythrocytes last about 4 months in the blood, platelets last around a week, and neutrophils are only in the blood a few hours before they exit into tissues). The class was about split between B and E, and I’m assuming it’s because I didn’t teach the point well enough.

I’m adding a point to everyone’s score for this question – so if you got them all right, you’ll see that your score is now 50/49.

Quick video on stomach vs. small intestine

Here’s the video I mentioned in class today. Stomach and small intestine can be confusing when you’re first learning this stuff – they both have glands at the bottom and other structures (pits in the stomach, villi in the small intestine) on top, and it can be hard to visualize all of that in 3D.

So I made a short video explaining the difference. I think it’s easier to understand if you can see someone drawing on the pictures. So here it is – I hope if some of you had the same problem that this will solve it!

You need your sleep. Really.

We talked a bit about the “glymphatic” system in the brain in class a while ago – and I wanted to share the TED talk I mentioned here, because it’s super interesting and super important. It’s sparked a flurry of research activity around the connections between lack of sleep and certain diseases, such as Alzheimer disease.  As Jeff Iliff explains, it turns out that while we sleep, the brain is not just sitting there doing nothing. Something very important happens in the brain during sleep – and it does not happen during waking hours.

The brain does more than clean itself during sleep, though. We know a TON more about sleep than we did even a few years ago – even about things that seem as incomprehensible as why we dream (fascinating!!).

Matthew Walker is one of the biggest names in sleep research, and his most recent book, “Why We Sleep,” is an easy and fun read (the audiobook is also excellent).

Or, for a more condensed version of his research, check out his conversation with Joe Rogan:

Lots of interesting facts, way beyond the typical “turn your phone off an hour before bed” stuff. For example: the World Health Organization has classified shift work as a probable carcinogen, based on the overwhelming research evidence that insufficient sleep is linked to significantly increased risk of certain types of cancer (colon, prostate, and breast). Yikes.

Here’s a really short video he put together that sort of summarizes all the bad things that happen if you don’t get enough sleep:

Oxytocin, high-fives, and exam performance

Here’s the article on oxytocin and exam performance I mentioned in class on Thursday. Oxytocin has been called the “cuddle hormone” because it has been shown to mediate trust, connection, monogamy, and basically any other good emotion that occurs in relationship with others. But you don’t have to cuddle to reap oxytocin’s benefits! This article talks at length about research showing how small, physical interactions (a touch on the arm, a high-five, etc.) have a positive effect on both the toucher and the touchee.

Some of the positive effects are what you’d expect: small touches have been shown to ease pain, soothe depression, deepen a relationship. But it turns out that small touches have another, more surprising effect: they can improve performance!  The article states:

“If a high five or an equivalent can in fact enhance performance, on the field or in the office, that may be because it reduces stress. A warm touch seems to set off the release of oxytocin, a hormone that helps create a sensation of trust, and to reduce levels of the stress hormone cortisol.”

How could oxytocin (a “relationship” hormone) have anything to do with personal performance? The article offers an interesting suggestion:

“In the brain, prefrontal areas, which help regulate emotion, can relax, freeing them for another of their primary purposes: problem solving. In effect, the body interprets a supportive touch as ‘I’ll share the load.’”

So: more high-fives, more touches on the arm, more secret handshakes around exam. It can’t hurt!

How to become 2.5 years younger

THIS is cool. And it involves the thymus, so it lines up well with our lectures!

Nature published a news article on September 5th entitled “First Hint that Body’s ‘Biological Age’ Can Be Reversed.” It summarizes a study in which the biological age of a small group of subjects actually reversed (yeah, you read that right, reversed!) following a year-long protocol involving three common drugs.

The study’s initial purpose was to see if drug therapy could stimulate regeneration of thymic tissue (remember how we said the thymus is biggest at puberty and gets smaller and smaller as you age?). But along the way, the researchers figured, hey, let’s also measure some methylation sites on the subjects’ DNA to see whether the treatment also affects epigenetic markers of aging.

Turns out the answer was yes on both counts: the subjects’ thymuses got bigger, and according to the DNA studies, the patients appeared an average of 2.5 years younger than when they started!

Okay, this is a small study, and it’s multifaceted, and there are always unintended/potentially dangerous side effects with drugs. STILL. SO COOL.