Introduction to The Medical Histology Atlas

Objectives and Format

Welcome to the Pennsylvania State University College of Medicine’s Medical Histology Atlas. It was created for the study of medical histology, and we welcome students in schools of osteopathy, dentistry, and veterinary medicine, and other allied health professions. The atlas can even serve in biology programs that teach animal and human histology. It is intended to be used as a companion to any histology course, and as a study guide for board licensing exams such as the USMLE Step 1, COMLEX, etc. It is not intended to replace a course in medical histology, but to serve as a companion to it. The atlas is geared more towards the laboratory portion of a course and is best used in conjunction with traditional lectures and textbooks. In fact, this Atlas is actually the culmination of 35 years of medical histology education at PSU’s College of Medicine. It is the combination of information from our laboratory manual with an extensive slide collection (of mostly human tissue, sometimes of monkey), and the level of information and order of its presentation is based on the original course. The versatility of this resource, however, allows students outside of PSU to go through the material in the order of, and at the level of detail directed by, their own course in histology.

This resource teaches basic medical histology and will serve as a basis for the future learning of histopathology, so there is very little discussion of pathology here. Some features of the Atlas include a comprehensive review of slide images and pertinent identifications at the end of each chapter, and, in select chapters, the use of images from Gray’s Anatomy (ADD REF!) to bridge gross anatomical structure of a tissue or organ to its microstructure. We have included multiple images at various magnifications, some with labels for orientation and many without, to facilitate full comprehension of the material, rather than simply learning one unique snapshot of a structure.

The authors of this Atlas have no bias towards any particular textbook of histology, and encourage students to use this along with their recommended or preferred textbook. This resource can be used as a stand-alone laboratory manual/atlas, or in conjunction with that recommended for use in a student’s histology course.

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Why Not Virtual Microscopy?

While the authors considered the use of virtual microscopy, there are many reasons why that technology is not employed here. First, the technical aspects of creating a virtual microscopy slide set are cumbersome and costly. The use of proprietary hardware and software is troublesome, and instead this Atlas uses a universal format which is simple to implement and update. There are also immense storage requirements for each section imaged for use in virtual microscopy, so there is a balance of the cost of storage space and server management with the size of the collection. This Atlas maximizes the number of examples of high quality images at various magnifications and limits the cost of managing the server.

Second, the educational goals of a medical histology course are to have students learn “normal” histology and don’t necessarily require scanning across a section, as would be crucial in a histopathology course. This is why we have opted to include so many different views, because learning the variations of normal will provide a platform on which students can later learn abnormal. There is also a balance of time spent by students mechanically navigating a slide using virtual microscopy vs. time spent actually learning the material.

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Why TWiki?

Readers will probably wonder why the authors chose to use the TWiki format for this Atlas. Perhaps the most important reason is the simplicity of changing the content in real time, either adding information or making corrections. Any registered user also has editorial rights, and the authors welcome feedback, suggestions, and comments on the material presented here. In this sense, the Atlas is actually a globally collaborative effort.

TWiki is also easily navigable and offers some advantages to students and frequent users who register, in addition to editorial rights. Each registered user gets their own unique user home page, where they can take notes and create links to parts of the Atlas and to outside websites.

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How To Use This Atlas

Scale of Structures

Given that this Atlas doesn't require the use of a microscope, some users unfamiliar with the microscopic world might find themselves having difficulty picturing the actual size of the microstructures about which they are learning. First, here is an introduction to some common units of measurement used in histology and electron microscopy:

Unit	Symbol	In Millimeters (mm)	In Angstroms (\xC5)	In Inches (")
Millimeter	mm	1 mm	10,000,000 \xC5	0.03937"
Micron	μ or μm	0.001 mm	10,000 \xC5	0.000 039 37"
Millimicron	mμ	0.000001 mm	10 \xC5	0.000 000 039 37"
Angstrom	\xC5	0.0000001 mm	1 \xC5	0.000 000 003 937"

Here are the dimensions of select structures seen in this Atlas:

Structure	Size in Microns (μ)	Size in Angstroms (\xC5)
Ovum	100 μ	1,000,000 \xC5
Skeletal Muscle Cell	10-100 μ	100,000-1,000,000 \xC5
Cardiac Muscle Cell	9-20 μ	90,000-200,000 \xC5
Lymphocyte	6-10 μ	60,000-100,000 \xC5
Erythrocyte	7.7 μ	77,000 \xC5
Ribosome	0.015 μ	150 \xC5

Navigating the Atlas

The atlas is set up by chapters based on systems and structures in the human body. Chapters are named for easy navigation and each chapter is on a single topic page. Several features will help you navigate the atlas, including a left menu bar, master table of contents page, topic page table of contents, and an alphabetized index of structures.

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Left Menu Bar

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Contents Page (Master TOC)

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Topic Page Table of Contents

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Using the Index

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Printing

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Images (How they work here)

• links in text
• gallery of thumbs for each section (fxn of hide/show, how the gallery works when you click on a thumb)
• table of IDs has clickable images
  • Tables are sortable by clicking Column Titles
• review of all slides and all IDs
• Tables are sortable by clicking Column Titles

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Why Register?

• Comments (editorial rights) for RUs
• User Customizable Topic Page
• User Customizable Left Bar

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