Histopathology

INTRODUCTION:- In the laboratory setting, numerous histological specimens are received throughout the day for testing. It is important to maintain a systematic approach to ensure that all samples are accounted for and are being received and tested appropriately. Without it, there is a potential to misplace or lose samples. OBJECTIVES:-After reading this lesson, you will be able to:- *explain the process of receiving surgical specimens *describe preparation of gross room *receive the samples, label the sample and store.  RECEIVING OF SURGICAL SPECIMENS:- At the time of receiving the specimens, following points should be checked and  these points must match between requisition form and label on the sample container. 1. Name of the patient 2. Sex and age of patient 3. Registration no, OPD or indoor number 4. Type of sample like appendix or lymph node. After matching the above points carefully, accession number of the Histopathology laboratory should be given on the requisition form and on the sample container like it has been depicted in the form and sample bottle. A register should be maintained for record and for future reference Following points should be noted on the register (sample given) 1.Date 2.Accession number which was given by the pathology department. 3.Patients name, age, sex. 4.Patients registration number/ OPD/ indoor number. 5.Type of sample. 6.Number of samples received from one patient. 7.Remarks / final diagnosis which may be entered later on. After receiving the samples the consultant should be informed for grossing. If grossing to be done after some time, fixative should be put in all the samples to prevent autolysis of the specimen. PREPARATION OF GROSS ROOM:-   The routine work associated with a surgical pathology specimen includes gross and microscopic examination. Proper preservation of tissues and processing of the tissue are the most important aspects for correct diagnosis. The size and features of the gross room depends on the number of specimens and type of institution. Gross room should be well illuminated and ventilated.It should have a gross station and racks to keep the specimen in order of accession number.        Gross station – It should have ventilated hood. 1. Cutting board placed inside the metal box designed in such a fashion that all the fluids should flow directly into the sink 2. Ready access to sink with hot & cold water 3. Formalin – stock and 10% buffered formalin 4. Box of instruments containing                 (a) Scissors                                                     (b) Forceps                                                     (c) Malleable probe                                       (d) Scalpel handle with disposable blades (e) Long knife                                                      (f) Scale                                                            (g) Pins for attaching the specimens to corked surface if required 5. Containers with different fixatives 6. Bone cutter 7. Large disposal bin 8. Box with cassettes and labels These are the essential items. Depending upon the pathology service being rendered to the institution more sophisticated items may be added. Apart from the above items following items may be of help in keeping the records 1. Photographic facility                                   2. Refrigerator                                                  3. Balance to weigh the gross specimen     4. X-ray view box 5. Other equipments for tissue bank facility.

Introduction:- Microscopes are instruments designed to produce magnified visual or photographic images of objects too small to be seen with the naked eye. The microscope must accomplish three tasks: produce a magnified image of the specimen, separate the details in the image, and render the details visible to the human eye or camera. This group of instruments includes not only multiple-lens (compound microscopes) designs with objectives and condensers, but also very simple single lens instruments that are often hand-held, such as a loupe or magnifying glass Objective:- After reading this lesson, you will be able to: *describe the principle of light microscope *explain the parts of a light microscope *learn how to use a microscope. LIGHT AND ITS PROPERTIES:- Light radiates in all directions, with each ray traveling straight till infinity, unless Amplitude:- refers to the strength of energy or brightness of light. When light passes through any medium, the amplitude decreases depending upon the medium. Wavelength:- The distance between the apex of one wave and the next is the wavelength and measured in nanometers, and determines the color. Retardation:- Media through which light is able to pass, will slow down the speed of light (proportionate to density of medium). Refraction:- If light enters a medium (eg glass) at an angle, a deviation of direction occurs Image Formation .                                                                                                                                       Focal point:- Parallel rays entering a simple lens are brought together to a single point called focal point, where a clear image will be formed. Conjugate foci:– Object placed at one end of lens will form a clear image on a screen kept at other side of lens. Conjugate foci vary in position. If object is nearer the lens, the image will be formed further away, at a greater magnification and inverted. This “real” image is formed by objective lens of microscope. If the object is placed within focal point of lens, image is formed on same side as object, is enlarged, right way up and cannot be projected on a screen, this is the “virtual image”. The eye piece of microscope forms this image Image Quality:- As white light is composed of all spectral colors, different wavelengths will be refracted to different extent. This lens defect is called chromatic aberration.Spherical aberration is caused when light rays entering at a periphery are refracted more than those entering the centre of lens. Both these faults can be corrected by using combination of lenses and lens elements. COMPONENTS OF A MICROSCOPE:- Light source:- Light source can be external or inbuilt. Dispersal of heat, collection of greatest amout of light, direction and distance are carefully calculated by the designers of microscope for greatest efficiency.   Condensers:-                                                                                      The purpose of condenser is to concentrate the light into the plane of the object. The more the light at the specimen, better is its resolution. All condensers have aperture diaphragm with which the diameter of the light beam can be controlled.                Object stage :-                                                                                    It is a rigid platform with an aperture through which the light can pass. It supports the glass slide. It allows controlled movement in two directions.                                                   Objectives :-                                                                                           They are the most important parts of microscope. The main task of objective is to collect the maximum amount of light from the object, unite it and form a high quality magnified real image. Magnifying powers of objectives are from 1:1 to 100:1.                                                                                               Body tube:- Body tube can be monocular, binocular and the combine photo-binocular (also called trinocular). Binocular tubes have provision for inter-pupillary distance adjustment, enabling each observer to adjust for his eyes.                                                            Eyepiece:-                                                                                             The final stage in optical path, the eyepiece’s function is to magnify the image formed by the objective within the body tube, and present the eye with a virtual image.                                           Use of the Microscope:-