Graduate
Microanatomy, 1998 Graduate
Microanatomy, 1998
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visitors since 12/17/97 Date of last revision: 07/19/01 |
Introductory remarks: For today's introductory exercises, you will use your knowledge of basic Cell Biology to develop hypotheses about ways cells could be structured to handle a particular function. After we set some ground rules for the group process, one of you will go to the board and write the results of your brainstorming. When you are done, you will then use the learning aids and resources in the next 1-2 days (text, lectures and laboratories) to answer these questions. In the Wednesday PBL session, you will discuss the answers and solve the problems. You will also see how close your hypotheses have come to the final solution. The group facilitator’s job is to keep the discussion moving and make certain all students are able to participate in the process. He/she will also help the group decide on some ground rules for the group process as well as lead the evaluation of the discussion itself. The facilitator is not supposed to "come up with the answers", nor are these sessions supposed to serve as "review sessions led by the instructor". These are student-driven sessions. We will provide the resources needed for reviews as the unit progresses. The TGIF sessions will help us identify if all the resources were adequate. Problem solving exercises on epithelia. 1) What is a working definition of a "tissue"? 2) Epithelia provide important gateways between body cavities and hollow organs and surrounding tissues. They are structured to solve basic problems for the body or organ. From your knowledge of cell biology, speculate about some ways in which the epithelial cells could be structured to allow the tissue to function: Not all epithelia perform identical functions; some are unique and have specializations. Think about how you might design an epithelial tissue in terms of cell size, shape, layers, surface specializations, or polarity to solve the following problems:
3) Epithelia are frequently polarized to allow for different functions at different surfaces. This week you will be asked to read a paper discussing the intracellular regulation of polarity in intestinal epithelial cells. It is: Achler, C., Filmer, D., Merte, C. and Drenckhahn, D. Role of Microtubules in Polarized Delivery of apical membrane proteins to the brush border of the intestinal epithelium. J Cell Biol 109: 179-189. We will discuss the paper on Wednesday, along with the answers to questions 1 and 2. A) In the meantime, from your studies of cell biology, speculate about ways cells could control polarity? Return to Top of Page
Learning Aids Assigned reading: Chapter 2, Epithelia in Bloom and Fawcett; Assigned paper on GI epithelial cell polarity (enclosed with this packet. See above for citation.) Read your text chapter and the assigned paper. On Tuesday AM, there will be a lecture/discussion on epithelia. You will have read your chapter by then and can participate in the lecture. Use the above questions to guide your study. On Tuesday PM there will be a laboratory focused on epithelia. Follow the guide in the Laboratory exercises (see next section). Completed lab exercises are due by the end of the day, Tuesday.
Laboratory Exercises--Epithelia General comments about the laboratory Each of you will be given a slide box for your own use during this course. The lab exercises are designed for independent study and learning. Video tapes that cover the laboratory material are available (along with a VCR) in room 116, Medical Research Building. See Dr. Childs, or Ms. Judy Hawkins for help with these materials. Some of the units may also have resources on web pages. Dr. Childs will announce when and where these are available. In the learning laboratories on the third floor, Basic Science Buiilding, there are lockers containing microscopes. One will be assigned to you at the beginning of the course. Since these are shared with other classes, they are available for use in the learning laboratories only. Please do not remove them from the laboratory site. If you choose to do the exercises during the scheduled laboratory period, the instructor will be there to help orient you with the specific slides. However, you may choose to do the lab exercises at any time and place. See Dr. Childs if you need access to a microscope away from the learning laboratories. The Department of Pathology may also provide access for their students. A word of caution...you may be tempted to do the exercises without looking at the slides via a microscope. This is not advised, because you will be at a disadvantage in later years when having to evaluate cell and tissue structure. Also, the microscope will be used during the examinations and you will need practice with this learning modality. Some of the questions in the laboratory exercise will require that you view the electron micrographs in your text. Turn in the answers to the lab exercises by 5 PM on the day of the laboratory. There will be a box in room 10-104 designated for lab exercises. These will be graded by the instructor of that unit. You will receive a maximum of 3 points on your final total point score if you have 100% of the answers right. Partially correct answers will also count towards your score. Return to Top of Page
Laboratory Exercise: Epithelia Exercise 1. In the skin, the epithelium is designed to protect us from the outside world. It is called the "epidermis". Examine the epithelium of thick skin. Find the boundaries and compare them with the photo below. Then, look at an electron micrograph of the thick skin in your textbook. Do not worry about divisions of skin at this point or the divisions of the epithelium. List the features that you see that might be protective. {Think about the various ways in which the skin protects the body from abrasions and invasion of unwanted substances}. Click on the small photo, below for a view of thick skin.
Return to Top of Page Exercise 2. Find the slide of the esophagus. Looking at the epithelium, what similarities and difference (s) do you see between the esophageal epithelium and thick skin? Do you see nuclei in the top layers of cells (top of photo=apical surface). How is this different from skin epithelia? Click on the following photo to see an enlargement of this epithelium..
Return to Top of Page Exercise 3. Find the slide of the jejunum. Look at the epithelium lining the lumen. From the position of the nucleus and the amount of cytoplasm on top of the nucleus, one can classify it by its shape. What is its shape? Click on the photo below to see a higher magnification of this type of epithelium.
Look at an electron micrograph of intestinal epithelial cell in your text. What specializations allow it to a) control entry of substances into the body? b) absorb food c) Secrete mucus. What would be the function of the mucus? d) transport water and ions across the basal surface e) communicate from cell to cell Check out the next photo and answer the questions underneath.
Return to Top of Page Exercise 4. Find the slides of the trachea and olfactory epithelium. Look at the epithelium lining the lumen. Look at the amount of cytoplasm over the nucleus and define its shape? Click on the photo below to see a higher magnification of trachea epithelium.
What specializations allow it to: a) transport mucus across the surface b) secrete mucus c) clean the air that we breath d) protect against entry of foreign substances Note the layers of nuclei in the tracheal epithelium. Does this signify stratification of that epithelium? Why or why not? Find an electron micrograph of olfactory epithelium in your text. What surface specialization allows us to detect smells? What does pseudostratified mean and how can you tell for sure if an epithelium is stratified? Return to Top of Page Exercise 5. Find a slide of the kidney. Note two types of epithelia based on the size, shape and height of the epithelium. Name them. Click on the photo below to see a higher magnification.
Which type might be specialized to allow passive transport of substances across the epithelial surface? Circle the epithelium. Why did you choose this one? Which type might be specialized for active transport or secretion of material? Give the reason for your choice. Return to Top of Page Exercise 6. Find the slide of the bladder. Also, find an electron micrograph of the bladder epithelium. Why is it called "transitional epithelium"? Click on the image below to see a higher magnification of the bladder.
How is the epithelium structured to: a) allow distention of the bladder b) protect against leakage of urine into the blood stream
Problem Based Learning 2 Epithelia Wednesday discussion Note: Your research during the past 2 days should have allowed you to find answers to the questions posed on Monday. These will be readdressed and discussed during this hour. In addition, you will be asked to evaluate the assigned paper. 1) Do you have a better working definition of a tissue? 2) How is epithelial tissue designed to perform the following functions:
3) In your review of the paper on polarity in GI epithelial cells, lets discuss the following.
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