On Monday, in our connective tissue lecture, we talked about hyaluronic acid, this incredibly huge glycosaminoglycan (over a million daltons – wow!) that does all kinds of things, including holding up to 1000 times its weight in water.
We talked about how it’s used in dermal fillers like Restylane and Juvederm. And I mentioned that old formulations of topical hyaluronic acid had just plain old huge hyaluronic acid molecules in them (so they just sat on top of the skin and – at most – did a little moisturizing) – but now, there are products that contain several different sizes of hyaluronic acid molecules (some even have HA packed into nanoparticles), so they can actually permeate the skin and add some resiliency. Nice!
So I thought I’d share some information on topical hyaluronic acid products here in case you’re interested.
First, here’s a great overview article on topical hyaluronic acid products from this great website called Into the Gloss. You may already know this, but in case you don’t: the creator of Into the Gloss, Emily Weiss, started a skin care and beauty brand called Glossier several years ago. The products are so good, and so reasonably priced, that they very quickly gathered a cult following – and in 2019, Glossier officially became a unicorn (a business valued at over 1 billion dollars).
Anyway – Glossier has a great hyaluronic acid product called Super Bounce that’s only $29. I was talking with a few students after class and one mentioned The Ordinary’s hyaluronic acid serum which is also really good, and only $13.50 (they have a ton of really high quality products at incredible prices – no idea how they do it!). If you have a favorite, email me, and I’ll post it here! Who knew histology could be so practical?!
Q. Why are the 2 central microtubules not a pair but the 9 pairs on the outside are considered pairs (instead of 18 microtubules) in the cilia? Is that because they are of a different type?
A. Thank you for bringing this up! It is confusing that we call this a “9+2” arrangement when it looks like there are 9 pairs of microtubules around the outside, and one pair of microtubules in the middle! Seems like it should be either “9+1” or “18+2.” There’s a good explanation, though. Here’s a diagram of an axoneme – we’ll talk about the “2” part and the “9” part separately below.
The “2” part of the axoneme The two microtubules in the center of the axoneme are totally separate from each other. So they can be considered to be 2 separate, independent units.
The “9” part of the axoneme The 18 microtubules around the outside are bound together, two at a time – so they can be thought of as 9 separate, independent units.
It turns out that in each of these 9 units, one of the microtubules is incomplete. If you look at the microtubules circled in red, you can kind of see that the top one looks round, and the bottom one looks like it’s not quite round, and has sort of just latched on to the top one. The bottom one is actually not a fully-formed microtubule (if you pulled the two apart, the top one would be round, and the bottom one would look like a C-shaped structure). So we really shouldn’t even call these guys “pairs” since they don’t consist of two fully-formed microtubules. The official name is “doublet” – and that is a little better than “pair,” I guess.
Here are some great questions about glandular cells!
Q. I wanted to clear up some confusion I have about exocrine glands and glandular cells types. I understand that there are 3 different glands; merocrine, holocrine, and apocrine. Within these glands with specific processes of secretion, there are different kinds of glandular epithelial cells; ion-transporting, serous secretory, mucous secretory, neuroendocrine, and myoepithelial cells. Is this correct? Continue reading →
Here’s the Ted talk I mentioned in class today that covers the way the brain cleans itself during sleep.
Very cool. Also, scary, because it’s become almost a badge of honor to get by with little sleep.
I recently read the book “Why We Sleep” by Matthew Walker. I sorta got sucked into it after watching him on Joe Rogan:
Here are the podcast notes if you’re interested but don’t want to watch the whole thing. 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 short video he put together that sort of summarizes all the bad things that happen if you don’t get enough sleep.
Tomorrow we’ll be talking about the events that happen in the first several weeks of life. It’s a really amazing process – you start with one cell, and then that cell turns into a ball of cells, and then a little flattened pancake appears, and then the pancake becomes three-layered, and then the pancake rolls up its edges to make a tube…and you end up with something that looks much more like a shrimp than a tiny baby!
In previous years, this lecture included a section on something called the pharyngeal arches. But it turns out that we talk about the pharyngeal arches in detail in Oral Histology (which makes sense, since the pharyngeal arches help form the oral cavity and head). So this year, to streamline things a bit, I deleted the pharyngeal arch content from our embryology lecture.
I just wanted to point that out, because the embryology summary videos and crossword contain content related to the pharyngeal arches, and that kind of discrepancy would drive me nuts as a student unless the course director explicitly said don’t worry about that pharyngeal arch stuff, it’s not on the test.
So I just wanted to let you know that none of the pharyngeal arch stuff will be on our exam. Sorry for the discrepancy!
Also, just a heads up, after cutting out that redundant content, our lecture is now shorter – we should finish in an hour.
It was so fun to meet you guys today! Thank you for your patience with the computer issues. It will NOT take that long to start class every day; apparently no one had been in the room so everything had been unplugged and needed to be rebooted.
I posted an updated version of today’s lectures slides on our lectures page. The main difference is that that this new updated version has some lecture objectives at the beginning. There are a couple other minor differences: I added a slide on what this class will be like, and I deleted the slide on toluidine blue slide (because it wasn’t super important).
I try very hard not to do this (go back after class and upload new slides), because I know it is annoying. But I really wanted you to have lecture objectives so you can see what I consider to be the most important take-aways from the lecture.
I’m so glad you liked the cookies! In case you didn’t get a chance to look at the diagram of your cookie(s), here are the drawings:
I’m so excited to meet all of you and start our General Histology course. Tomorrow is our first class session together (yay!) and I just wanted to tell you a few things so you know what to expect.
Obviously, you’ve made it to our website, GeneralHistology.com. This is where all of our course stuff will reside. Here’s a quick summary of what this website contains:
Our Home page (the page you’re on right now) is where I’ll post anything related to the course (student questions, schedule changes, stuff I run across that’s related to what we’re talking about in class, etc.).
The About page has the basic information you’ll want to know about our course. You can also download our course syllabus here, which is very long and boring but has all the official school policies in it.
Our class schedule is listed on the Lectures page. You’ll also find the PowerPoint slides for each lecture here, as well as the lecture recordings (I’ll post these as soon as they’re available – usually they’re ready a few hours after lecture).
The only thing not on this website is grades; these will be posted on Canvas.
So that’s about it for the website. Tomorrow, we’ll have class at 1:00 – and although the schedule says we have class until 2:55 we’ll probably end earlier than that. I’ll spend a little time at the beginning just talking about the course, so you know what to expect. Then we’ll have a short lecture to introduce you to some basic principles of histology.
Also, we’ll have a yummy AND educational surprise tomorrow in class. I’ve been working hard on it this weekend (actually, it’s not work, it’s really fun)…here’s a sneak peek:
Hello! If you’ve found your way here, you must be an incoming first year student – welcome! I’m SO excited to start our course and meet you!
I’m in the process of updating this website to fit what we’ll be doing this year – so there will be some changes here and there over the next few days. But feel free to poke around and see what’s here. And if you have any questions, please email me at email@example.com.
Class starts in just 11 days – so I hope you’re enjoying these last sunny days of freedom! I look forward to meeting you and talking about some really interesting and beautiful stuff in our histology course.