Respiratory tree drawings

Tomorrow we’re going to be talking about the histology of the respiratory system. It’s kind of like the GI tract, in a way, in that it consists of a series of tubes that have different histologic features. So it’s pretty easy to break down into parts (bronchi, bronchiole, etc.) and summarize.

I like to make drawings to summarize things like this – and I thought I’d share this one with you in case you find it useful. It shows how the wall of the respiratory tree 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 🙂

Unlabeled:

Labeled with passageways only:

Fully labeled:

Question about muscularis layers in GI tract

Q. I am slightly confused about muscularis externa. Is muscularis externa only present in places where muscularis mucosa is not? For example, the oral cavity, upper esophagus, and anal canal. Is it possible for them both to be present? And muscularis is not always present as a layer in the GI tract, correct? When present does it typically present in the same layer that the muscularis mucosa would be?

A. Those are great questions! As you noted, there are two “muscularis” layers in the GI tract: the muscularis mucosa and the muscularis externa.

  • The muscularis mucosa is a thin little layer of smooth muscle that is part of the mucosa (which includes epithelium, lamina propria, and muscularis mucosa). It innervates the inner layers of the mucosa, and it also shows you nicely where the mucosa ends, and the submucosa begins.
  • The muscularis externa is a thick layer of muscle that provides the main structural support all along the GI tract. It sits between the submucosa and the serosa/adventitia.

Basically the GI tract is just a tube with four concentric layers, like this:

From inside to outside, there’s mucosa (epithelium, lamina propria, and muscularis mucosa), submucosa, muscularis externa, and serosa/adventitia.

All levels of the GI tract have this exact structure, except for:

  • the mouth (which I’m not allowed to discuss with you lol)
  • the anus (which is only slightly different…its mucosa is comprised of just epithelium, with no lamina propria or muscularis mucosa).

I think that pretty much covers it.  Having said all that, here are my direct answers (in blue)!

I am slightly confused about muscularis externa. Is muscularis externa only present in places where muscularis mucosa is not? For example, the oral cavity, upper esophagus, and anal canal. No. Both the muscularis mucosa and muscularis externa are present at every level of the GI tract except for mouth and anus (as mentioned above). The upper esophagus btw is not an exception – it has the same four-layered structure you see everywhere else. Is it possible for them both to be present? Yep! And muscularis is not always present as a layer in the GI tract, correct? No – both types of muscularis layers are pretty much always present. When present does it typically present in the same layer that the muscularis mucosa would be? No – the muscularis mucosa is always part of the mucosa (the innermost of the four layers), and the muscularis externa is always located between the submucosa and serosa/adventitia. 

Quick video on stomach vs. small intestine

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. I hope if some of you had the same problem that this will solve it!

Information about Exam 2

This post contains specifics and logistics for exam 2 in General Histology (DDS 6214). Please email me if you have any questions not answered here! I’ll send out an email with the password to the exam a little before midnight tonight 🙂

Start and end time

The exam is scheduled for tomorrow (Friday, September 17), and you may take it any time between 12:01 am and 11:59 pm that day. Once you open the exam you have a maximum of two hours to complete the exam. All submissions must be uploaded by 11:59 pm on Friday, September 17, in order to receive a grade.

Content

There are 36 questions on the exam, and the lecture breakdown is as follows:

Blood: 7 questions
Hematopoiesis: 5 questions
Lymphoid system: 8 questions
Cardiovascular system: 7 questions
Endocrine system: 9 questions

Examplify Information

You will take this exam using Examplify installed on your PC/Macintosh laptop or desktop computer. If Examplify is currently installed, it may require an update and computer restart before the exam If it is not installed, you should download and install the most up-to-date version of Examplify before the exam.

This exam will be remotely proctored using ExamID and ExamMonitor. This means you will take a photo of yourself at the start of the exam for identity verification and you will be recorded during the exam. Thus, only laptops/desktops with a working camera & microphone and Chrome or Firefox browsers can be used to complete the exam. Please note, iPads are not compatible with the ExamMonitor software and may not be used for this exam.

I have enabled the digital notepad and highlighter within the Examplify software. There will be no scratch paper allowed. Also, just as if we were in the classroom, there will be no additional electronics allowed such as phones, tablets, smart watches, headphones, etc.

If you experience any anomalies while taking the exam (examples include barking dogs, interruption by a family member, etc.) please email me at kkrafts@umn.edu immediately after completing the exam to let me know.

Please access this link for a quick troubleshooting guide for Examplify for your reference.

Grading

After you take the exam, you will immediately receive your raw score. Final scores will be posted to your ExamSoft Student Portal as soon as possible after I have had the opportunity to review the exam metrics (I hope to be able to do that on Saturday morning).