A&P 1 Histology Lab Week 1 In-lab Guide Epithelial Tissue ID: Squamous Tissue Lab Exercises with a special section on microscope use In this "In-lab Guide", we will be looking at squamous tissue. We will also be learning some basic skills with the microscope. YOU WILL NEED THE IMAGES IN YOUR TEXTBOOK OR LAB BOOK! Our lecture book has an excellent section on the tissues, including summary tables. There are always extra books in the room! PLEASE NOTE: Your group will be needing a microscope at the workstation. All of the steps in this guide are designed to be done at the workstation. If there are other scopes, DO NOT use a microscope that is already set up in the room, being used as a demo. Those are for another class. ALSO NOTE: This document uses terms you learned in the Microscopy lab, and is giving you a chance to use them. Make sure you understand those terms! The Steps found in this In-Lab Guide should be done in the order they are found. NOTE: if you have had microbiology, or some other college-level course that uses a microscope, and you feel comfortable with a microscope, you can skip this and use the alternative Pre-lab. If you have not had a class such as this, I encourage you to get a person in your group who has! I do not care about your ability to use a microscope! Please move through this as quickly as you can! Have one person talk through the document, while another person works the scope. Pick the person with the most experience to operate your scope. I do not care about your ability to use a microscope. Make sure everyone in your group looks into the microscope when I direct it! I will be walking around the room, helping you. If there are very few students with experience with microscopes, I will often read these instructions to you while you are working. This moves us along faster!
Step 1. ID Stratified Squamous Tissues, and learn some important lessons about microscopes, pointers, and tissue slides. Please move through this as quickly as you can! Have one person talk through numbers 1 8, while another person works the scope. Pick the person with the most experience to operate your scope. I do not care about your ability to use a microscope. #1 You will be working in groups of 3 or 4. Here s a job for each person to get ready: 1. Send 1 person to go get a slide that says Esophagus. Set it on your desk. 2. Have someone else open a lab book or lecture book to an image showing you stratified squamous. Use the index! Look in the HISTOLOGY chapter. 3. After reading this paragraph, another person should go get a microscope. Always grab a microscope by its handle and base. The accompanying image is showing you how to carry one. Be careful they are heavy! We keep our power cords in labeled drawers around the room. Get one of the cords & plug in your microscope. Don t turn it on yet. 4. Select a person to be in charge of using the microscope. It should be a person experienced with microscope usage. 5. Choose someone to read these instructions to the person working the microscope. #2 Find these parts on your scope you see in image C. Depending on exactly which type of microscope we have in the room, the Off/On button and light intensity knob might be in a different spot. Notice that the objective lenses can be changed by rotating them. Always make sure the objective lenses are set on the lowest power (the objective lens marked 4x ). This is called scanning power, because you use it to scan around. C How will you scan around? Most stages have knobs attached to them that move the stage up & down, right & left (not seen in Image C ). Find these knobs. Yours might look different. the Off/On button and light intensity knob might be in a different spot!
What idiot #3 Click your scope on, after reading this paragraph: If the decided - light does not turn on immediately, it is because your light means on?? intensity knob is set all the way down to its lowest setting (As it should be! That protects the light bulb from blowing out when you turn the scope on!). Please try to remember to do that when you are done with your microscope today! OK, turn it on. Without looking into the lens, turn that intensity dial away from you, all the way, until it can t go any farther, and then turn it all the way back towards you, watching as the light becomes stronger and weaker. Do it a couple of times! Now, set the dial somewhere in the middle, or lower, because I am going to ask you to look in the eyepiece, without a slide, and I don t want to fry your retinas. Believe it or not, I encourage students to look into a microscope with just one eye, placing your left eye on the right eyepiece, or vis a versa. It makes focusing MUCH easier! I know, I know other science teachers tell you to keep both eyes open, but that is silly unless you are going to become a scientist. I keep one eye closed! The truth is they usually do, too! Another thing if you wear glasses, take them off. If you do not, you will not put your eye against the lens, leaving a gap so you won t scratch your glasses. You will always struggle with focusing. And that eyepiece is a much better lens than your glasses, so you will make up for it when you focus! Look in one eyepiece with just one eye!!!! Now look in the other eyepiece. Notice that there is a pointer in one eyepiece only. Sometimes it is on the left, sometimes on the right. So if you ever are asked to ID something at the pointer, and you do not see a pointer: open your other eye! Duh! Pull off the lens that has the pointer (they slide off), and hold it up to the light in the ceiling. See the pointer?? Put the lens back on. Notice you can rotate the pointer by turning the lens. #4 Look at the accompanying image. You see a thin slice of an esophagus, without stain. Notice that you cannot see much in the way of layers or structures. So we stain them. The staining is different shades, depending on the fat and protein content of the cells and tissues. Staining the slice lets your brain see things much more clearly. Sometimes you will see the whole organ on the slide, especially if it from a mouse or other small animal. If it is from a larger animal, like a human, they will only give you a small piece (see box on image), but making sure you get a representation of all the layers you need to see (if present). Sometimes, if it is an older slide, the stain evaporates, as seen in the image. You should make sure you get the darkest slide available in the slide tray! Usually, when I have you look at a slide, I will start by having you simply holding it up to the light and orienting yourself. That way, you know what you are looking at! If it is a visceral organ, you should always find the lumen this way. Although there are other white areas on the slide, the lumen is the ocean of white. Do not assume the lumen is up as they might have taken the piece from another part of the tube!
#5 Go ahead and hold yours up to the light, letting everyone see it before putting it in the scope. Discuss where you think the lumen is on your slide. Notice that there is always more than one tissue on the slide, so you are going to have to move the stage & slide around to see what you want to see! Here, we want to see the mucosa, which is next to the lumen. Using the image on the previous page, figure that out! Clip the slide onto the stage. Look and make sure your tissue is under the objective lens if it is not, move the tray using the knobs until it is! Look in and focus, using the course focus knob to get it close to focus, then the fine focus knob in order to get the edges as crisp as you can. Notice that your field of view cannot get everything you saw while holding up the slide that is because your total magnification is 40x. Think of that as you are 40 times closer than you were when you held it up to the light! Remember: I had you start at the lowest power (scanning), so move the stage around, using the knobs that move the stage. You will notice that everything is flipped when you try to go right, the slide will appear to move left. If you ty to go up, the slide will appear to move down. That is because the lens is flipping the image. Don t worry you ll get the hang of it. Yours will look different. It might be upside down, or the lumen might be to the side! Try to get the mucosa under the pointer, with a good amount of lumen in view because when you go to a higher power, the field of view will zoom in closer to the pointer! Once you have this slide in focus, you will never have to use the course focus at higher magnification, because these microscopes are parfocal! Once there, let everyone take a look, remembering you are 40 times closer than you were when you held it up to the light! Some people will have to fine focus for their own vision, especially people who took off their glasses. or or #6 The truth is, this magnification is fine for identifying this tissue. We are next to the lumen, and there are several layers of cells (notice how far away the basement membrane is from the lumen). And we can see the submucosa. But If you are inexperienced at looking at slides, you probably aren t sure what a cell is yet, let alone the basement membranes, right? Rotate the objective lenses to the 10x (100x total magnification). You are now 100 times closer. Fine focus it again. Don t even think about touching the big knob, or you ll break the slide!! Get your pointer close to where it is in this image. How about now? Does your brain know what a cell is yet? Let s move on and make sure.
#7 Rotate the objective lenses to the 40x (400x total magnification). You are now 400 times closer. Re-focus with the fine focus only! The cells are shaped like a cat s eye. The nuclei stain dark. Some cells are missing nuclei (they might have popped out when they made the slide! The basement membrane is dark and wavy! Make sure everyone in your group knows what a cell is! TIP! Draw what you think a cell looks like! Make sure everyone in your group agrees! Remember I told you in the videos Remember I told you, in the videos, that the cells can look different down by the basement membrane than they do near the surface! #8 Now, a magic trick! Go back to the previous magnification. Re-focus. Look! You can still see cells! Now go to the lowest scanning power. You can still see the cells (Sort of)! More importantly: you do not have to see the cells to know what type of tissue it is! #9 And now I teach you a trick that will help you get ready for the lab practical better than actually looking at slides in the Learning Lab. It is called a Google Search. (Just take a look now, and try it at home. I will put these links in the slide box on the Lag Guide page) Click on this link. This is a google image search using the terms Stratified Squamosal Esophagus Scroll down the page. Ignore ones that aren t pertinent. Notice there are various magnifications. ID on each: Lumen Mucosa Submucosa Squamous cells Basement membrane You can still see cells! Here s what it looks like in the epidermis (it is just thinner): Stratified Squamous Skin You may be tested on this tissue at 100X or 400X. In the videos, I told you to come up with a descriptor term for each slide. Take out a clean piece of paper and label it Stratified squamous epithelium. Make a drawing of the tissue, if you d like. Under it, write down your Descriptor Term. Under that, write down some representative locations for this tissue. If your instructor mentioned any, make sure you write them down! Write down any extra information your instructor wants you to know (special cell names, etc.). If the answer is "none", just write that!
In the lab room, there is a Wall Chart labeled "Epithelial Tissues", with an example of Stratified Squamous Tissue (see green box accompanying image). Go look at the chart if it is available, or use the photo below The cells in the first photo (extreme upper left of chart) look VERY different than what we just saw with the esophagus. See the close-up view Explain why they look so different.
Step 2. ID Simple Squamous Tissues #1 #2 There are several slide trays in the room. Each tray has a different set of slides. Go and get a slide from the slide tray marked "LUNG". Now, we are going to clip it onto the microscope s stage. Make sure your scope is on low power (4x = 40 total magnification). Now, following the numbered instructions below (1-3), look in the eyepiece. 1. Move the slide around until you see something like this view. 2. 3. #3 Fine focus it again. On the microscope (not the photo), can you see a cell? A nucleus? Can you see cell shape? Don t even think about touching the big knob, or you ll break the slide!! Does your brain know what a cell is yet? Let s move on and make sure. #4 Put your pointer into an area as indicated above. Rotate the objective lenses, moving up to 10x (100x total magnification).
#5 Now, we will zoom in. Find something that looks like the insert photo below (labeled 100X). Now, following the numbered instructions below (1-3), look in the eyepiece. 1. Move the slide around until you see something like this view. 2. 3. Fine focus it again. On the microscope (not the photo), can you see a cell? A nucleus? Can you see cell shape? Don t even think about touching the big knob, or you ll break the slide!! Does your brain know what a cell is yet? Let s move on and make sure. #6 Put your pointer into an area as indicated above. Rotate the objective lenses, moving up to 40x (400x total magnification). 1. 2. 3. Move the slide around until you see something like this view. The cell s shape is not immediately obvious. The nuclei stain dark. You do not really have to see the plasma membranes to know where the cells are if you keep track of the nuclei. Make sure everyone in your group understand the drawing on the next page! If someone in your group still cannot see the cells, MAKE THEM TRY TO DRAW IT! This forces their brain to see! See next page for the drawing I made in college (in 1985!).
#7 This is what you are seeing on the last photo on the previous page: But wait! Where is the lumen? The center of the sac (1) and the blood vessel (2). In most of the lung, we are not going to see submucosa, muscularis, ect. Your lung is a bunch of microscopic sacs called alveoli, with blood vessels running through to pick up oxygen. Can you see it? You may be tested on this tissue at 100X or 400X. 2. 1 On the piece of paper you drew and took notes on Stratified squamosal, do the same for this tissue. Write down your Descriptor Term. Under that, write down some representative locations for this tissue. Write down any extra information your instructor wants you to know (special cell names, etc.). If the answer is "none", just write that! #8 Want to take a quick look at more examples? Click on this link. This is a google image search using the terms: Lung slide 400x Notice I added the power, so you wouldn t waste time looking at slides at scanning power. Keep this in mind! #9 Do you see the image on the right? This is what you just did. You are going to repeat this process for the other slides. I usually suggest you make yourself a simple drawing when you reach the magnification I will be testing you at. But it is not mandatory if that does not help you. Then, zoom back out, fine focusing each time, and make sure your brain knows what a cell is. Under the drawing, write down your Descriptor Term. Under that, write down some representative locations for this tissue. Write down any extra information your instructor wants you to know (special cell names, etc.). If the answer is "none", just write that!