INTRODUCTION TO THE LAB

The lab is devoted exclusively to the microscopic study of  slides. Almost all of them are of mammalian tissue and organs, including many specimens from human beings. The slides are of professional quality—the kind you would see in a pathology lab—and, for the most part, beautifully stained.

What you're supposed to do in lab is learn to think histologically! What's really challenging about the lab is trying to see the material spatially in three dimensions and temporally in four dimensions. For example, if a section has many circular profiles of similar tissue, you might imagine that the profiles were connected in a coiled tube, while if a section has cells sharing the same space but with different characteristics, you might imagine that the cells were differentiating from a common source. That's thinking histologically! And what would you imagine was going on in a cell with a vesicular, salt-and-pepper nucleus, a large nucleolus and a basophilic cytoplasm? And what about…? etc.

So what are you supposed to do in lab? Prior to thinking histologically, you have to know what you're thinking about. Your first objective in the lab, therefore, is to sift through what you see on slides, and learn to recognize every tissue and cell type broadly and specifically. In other words, learn everything on the slides backwards and forwards. The work is intended to be accumulative, however,—building on itself—so what you learn one time is of value another time. I don't expect you to learn everything about the slides the first time through, and you shouldn't either! Give yourself a break and the material time to sink in. The labs will actually get easier as the material gets more familiar.

You must bring Eroschenko, V. P., di Fiore's Atlas of Histology with Functional Correlations, 9th edition. Philadelphia: Lippincott Williams & Wilkins; 2000 to lab. It has excellent and realistic pictures of most things you will be expected to know, but not everything is illustrated (e.g., whole mount of muscle spindle), and some things illustrated are not represented in your slide sets (e.g., section of sympathetic trunk ganglion). Regrettably, some of the illustrations are idealized (e.g., the layers of the cerebral cortex) and misleading, but the Atlas should serve well as a guide for identifying tissues and cell types and should be your constant companion in lab.

You will be supplied with a compound microscope of professional quality, and I’ll teach you how to use it correctly to study the slides. You are expected to adjust your microscope before beginning each lab and use the instrument correctly throughout the course. Otherwise, you're not optimizing your opportunity to learn and may even reduce your ability to identify structures correctly. You are expected to draw, label, and take notes on what you see, but your drawings will not be evaluated or graded. You will have to supply your own drawing material (pencil [you may use colored pencils], sharpener, plain white paper [no lines please!] and eraser). Only one drawing should be placed on a page, although you may use parts of the same page for views of the material at different magnifications. Include all the information given on the slide label as well as magnification on your drawing. You will probably find that your drawings are the best source of information you will have for preparing for practical exams.

So what about the practical exams? You are expected to know these slides so well that you can identify any structure seen in the microscope virtually instantaneously.  During the practical exams, you will have forty-five seconds to make each identification, and that's a generous fifteen seconds more than you should need.

LABORATORY EXERCISES

In all, you have eleven laboratory exercises. I'll supply you with these, or you can download them on line by double clicking the entry on the lab schedule (below). These exercises are assigned for the dates listed, but you may use the slides at other times as well. As you will see, the slides have been placed in seven Histology Slide Collections. Each week, you are required to find all the assigned slides in one or another of the collections (see individual lab exercises for slide numbers and collection), although you may not be able to view all the slides in order, since other students will be viewing slides and the collections have fewer than 18 slides of any type. You are, nonetheless, responsible for all the assigned slides. After studying a slide you are expected to return it to the proper collection so other students can find it there.

You are not responsible for drawings or preparing laboratory reports, although I will examine your drawings and comment on them. I will frequently draw what I see through your microscope in order to illustrate a point, so you should have drawing paper and a pencil at hand.

The laboratory operates informally in general with the exception of one item of laboratory etiquette. In the event you ask me a question regarding a slide or when I stop at your microscope on my tour of the lab, histology etiquette requires you to relinquish the lab stool. I will take your place and sit while looking through your microscope. Be sure it is adjusted correctly, since I will be unable to answer your question or ask one of my own if your microscope is poorly adjusted. If you notice that I have abandoned you, adjust your microscope before I come around again.

Each practical exams will have 25 questions, one at each microscopes (with one rest stop). You will have 45 seconds to answer each question and will move in file around the room through all the questions. The questions are typically, ‘What is at the tip of the pointer?' At the end of the practical, you will have 30 seconds to change answers, but you may not revisit any microscope. Your help in placing the microscopes before the exam and replacing them in their cabinets afterwards is appreciated.

At the end of the term, following the last practical, you are expected to restore all the slide collections to their pristine condition. Your participation in this exercise is required but need not be a burden and is generally accomplished in the spirit of a party.

HE: the section was stained with hematoxylin and eosin,
IH: the section was stained with iron hematoxylin,
Other stains are also be indicated on the label, such as Mallory's trichrome, Golgi, silver impregnation, etc. which will be discussed in lecture.

A caution: You must never view thick hole mounts and ground preparations with the high-power objective! They will be destroyed by the high-power objective, and the objective is liable to be scratched.

send me e-mail: sshostak@pitt.edu
last revised: Nov. 22, 2004