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Necropsy
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Objective :

  • To learn the procedure for performing necropsy in rats to uncover the cause of death by defining possible etiology and pathogenesis to arrive at a diagnosis.
  • To learn the anatomical structure of the different organs of rat.

Principle :

            The examination of dead or terminally ill animals offers opportunities in studying the processes involved in disease situations. Various medical imaging techniques have evolved in recent years providing adequate information on the morphologic alterations of organs and tissues following disease. However, necropsy still provides a firsthand look on what really happened along the course of the disease. In poorly understood disease situations, tissue alterations resulting from or as a reaction to the disease process may or may not be detected during clinical examination. Results of clinical examination alone may not be sufficient to define the process involved. Thus, gross and microscopic examination of diseased organs and tissues may lend valuable information in understanding the pathogenesis of a disease.

            Morphological changes when correctly recorded and interpreted provide a basis for correlating functional changes seen in a particular disease process. Not all disease processes will show dramatic morphologic alterations in organs and tissues. Some clues may be derived however from necropsy examination that will provide valuable information in the recognition of such functional disturbances. The challenge is on the examiner to recognise these clues.

            The purpose of necropsy does not end on the recognition of the lesions alone. Skillfully performed necropsy with all the information gathered, accurately recorded and interpreted will provide valuable assistance in the formulation of animal health and production strategies aimed to prevent and control animal diseases in a herd or flock. Yet, the usefulness of necropsy resides on the application of the information gathered in the formulation of appropriate treatment, control and disease prevention measures.

Theory :

            The post-mortem examination of an animal is called a necropsy (nec - dead, opsy - to view).  Necropsies provide important information about the cause of death and this information can be used in a wide variety of ways. Necropsies on animals are routinely performed when a new disease breaks out, to determine which animals carry the disease and what the effects of the disease on animals might be. Scientific researchers also necropsy the subjects of their research to learn more about how their research is working in living systems. Experimental animals are sacrificed / euthanised  (avoid the term 'killed') for various reasons. These include the need for cells or tissues for in vitro research; for blood, tissues or other samples at certain stages of a study or at the end of a study; for veterinary pathology or diagnostics; to prevent unavoidable pain and distress when the approved endpoint is reached; and to cull animals that are no longer needed (e.g., from a breeding program) when no other use consistent with the tenet of the Three Rs can be found for them. Whenever an animal is killed in the course of research, teaching, testing or production for scientific purposes, it must be done with respect and in a way that ensures the death is as painless and free of distress as possible.

            Providing a complete history of the animal is extremely important because it will provide the veterinarian and the pathologist with pertinent background information which increases the chances of finding the true cause of death. Changes in tissues occur as soon as 20 minutes after an animal has expired. Since these changes may obscure the true cause of death in an animal, it is important to sample tissues as soon after death as possible for an accurate diagnosis. This is particularly true if the weather is hot, the animal was febrile (had a fever), or when disease symptoms suggest involvement of the gastrointestinal (GI) tract. For these reasons it is important that the animal be examined as soon after the time of death as possible and tissue samples should be properly collected and thoroughly chilled until examination. In the use of animals in science, it is essential that the scientific community take on the mantle of responsibility for applying scientific judgment and up-to-date knowledge to ensure that this is achieved. Euthanasia means a humane killing / gentle death in the context of animals used in science. The most important criteria for acceptance of a method of euthanasia is that it have a rapid initial depressive action on the central nervous system (CNS) to ensure immediate insensitivity to pain, and that steps are taken to minimize distress in the animal prior to the procedure.

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