Histologist Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Histologist and links to relevant pages within the course.
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The focus of this course will be on the technical process of producing human tissue blocks embedded in paraffin wax. Other embedding techniques using various media such as gelatin, ester wax, polyethylene glycol, and epoxy resin are also used in some histological techniques. However, in this course we will be discussing the method of embedding human tissue samples in molten, or melted, paraffin wax. This is the most commonly utilized method for routine tissue embedding and is the method most utilized in nearly all hospital histopathology laboratories for processing human tissue samples for diagnostic interpretation.In the order of events (chronology) of the total histology process, paraffin embedding takes place following tissue processing and prior to and in preparation for microtomy. For proficiency in paraffin embedding, the histologist needs:An understanding of basic anatomy for use in tissue type orientationKnowledge of basic tissue sampling methods used in gross dissectionTo develop manual dexterity and spatial reasoning in order to correctly orient the specimen in the tissue block for microtomyThis course will introduce and review some of the essential background information needed for correct embedding technique. Also discussed in this course will be guidelines for orientation of common histology specimens. Mastery of this information facilitates practice and application of these concepts during execution, to increase the histologist's technical proficiency at paraffin embedding in the histology laboratory.
|Basic Anatomy and Tissue Identification|
The embedding histologist must practice to develop rapid visual recognition of tissue types and be able to determine the correct orientation for each specimen using their knowledge of anatomy and tissue sampling techniques. It is often helpful to consider the reason(s) that each specimen may have been selected for submission to histology. Also, remember that clear goals are outlined for each specimen to arrive at a diagnosis based on the type of specimen and the suspected reason for the surgical procedure performed.Gross dissection of tissue samples is determined by a pathologist or pathologist's assistant (PA). Many laboratories follow established protocols for the gross dissection of particular types and categories of specimens. Specimens are identified using a numbering system that associates a unique number with a specific patient, medical record number, and tissue sample upon receipt. The cassette containing the specimen from that unique patient and procedure is also identified with this number. This unique number is transcribed on the slanted top edge of the tissue cassette by either hand or machine, shown in the lower image. The slides prepared from the block in the histology lab from this cassette are likewise identified with this unique number, as shown in the image on the right.Tissue is selected for microscopic examination to document important details about each specimen. Some examples of specimens that may be selected for submission to histology include:All lesions grossly identified - Tissue between lesions may be included with the lesion to determine if the lesion is separate or interconnected to surrounding normal tissue.Representative sections of all normal tissues or structures that are not included with suspected disease-containing sections.All surgical margins, when appropriate.Frozen-section remnants for permanent sections.
|Spatial Reasoning and Visualization|
Histology is literally, "the study of tissue." Tissue sections cannot be produced which are completely accurate and representative "snap shots" of the tissue in its' living state. But instead, histologists seek to preserve the tissue in the most life-like state possible. In reality, what we are able to achieve is a somewhat distorted, yet permanent, representation of the tissue's living condition.Histologists must learn to be able to visualize how specimen handling, including gross dissection and tissue processing, affect the appearance of tissues at both the macroscopic and microscopic levels.A clear understanding of anatomy and the ability to spatially visualize the specimen in three dimensions is extremely helpful. The histologist must use this background knowledge and understanding to visual identify any alterations in the tissue appearance caused during gross dissection and/or tissue processing; Apply this insight for correct specimen orientation during embedding.In visually assessing and identifying tissue samples, note that: Some sections cut through tubes or invaginations are not large enough to show the entire lumen. Many cells and tissues are organized into partitions, which divide the structure into numerous smaller areas which may be transected in any given specimen.Many submitted specimens may not show all the structural details that are depicted in images in histology atlases or anatomy textbooks. You may become quite skillful at visually identifying many specimen types, but you MUST still verify the specimen type using an electronic or paper-based worksheet.
|Specimens Containing a Lumen|
Any specimen that is a transverse section of a hollow structure or a specimen containing a lumen will almost always be placed in the block face to show the lumen or other opening in cross-section on the final slide. For any organs with very large lumen's in which the tube has been transected, you will embed on the cut surface to demonstrate the lining and layers present. Of special concern are specimens with very tiny lumen openings, such as temporal arteries or vas deferens. Since the lumen opening is so tiny, it is sometimes difficult to see. Some laboratories may lightly dip the end of the tiny tube opening in black ink. This indicates the "end" that should be placed down in the block face. Some laboratories may submit such tiny tubes whole and ask that they be cut into cross-section at embedding. This allows the histologist to clearly see the opening during dissection. Other means to flag these specimens can be by using an abbreviation on the cassette such as "vas" for vas deferens, alerting the histologist that the specimen contained will need to be embedded on end to show the lumen in cross-section.
|On all of the following specimens, the histologist is given the embedding orientation instructions to "embed on edge." For which specimen is this orientation NOT appropriate?||View Page|