Pathology (Greek „pathos” – suffering and „logos” – science) is a visual medical discipline that studies disease changes in the human organism at the organ, tissue and cellular level. It also provides morphological diagnostics for clinical practice. This is essential for all surgical medical specialties, as well as for a number of others – pediatrics, gastroenterology, rheumatology, skin diseases.
In our country (Bulgaria), there are two main sections of pathology – general and clinical pathology.
General pathology studies the morphological changes of pathological processes. It is closely related to preclinical medical disciplines – biophysics, biochemistry, genetics, pathophysiology, microbiology, immunology, pharmacology. The main sections studied by general pathology are intracellular and extracellular degenerations, circulatory disorders, inflammation, immunity pathology, regeneration, compensatory-restorative and tumor processes.
Clinical pathology (systemic, special pathology) studies the morphological changes in the organs in individual diseases (the so-called „nosological units“, from the Greek „nosos” – disease). In the countries of Western Europe, USA, Canada, Australia, an analogue of our Clinical pathology is Surgical pathology. In these countries, there is also a separate specialty of clinical pathology, but it has a larger scope and also includes clinical laboratory, microbiology, immunology, parasitology.
Pathology deals with various generally biological and social medical concepts:
Health – a sustainable dynamic equilibrium with the environment, in which the correspondence between structure and function of the organism allows it to realize its biological potential. It is related to maintaining the constancy of its internal environment, the so-called homeostasis.
Illness – disruption of the balance in the body, due to changes in the environment or weakness of the individual’s biology (e.g. in the case of genetic diseases). The disease manifests itself with functional and structural changes.
Etiology – science of the causes of diseases (Gr., aitia – cause). Knowing the etiological factors gives a chance for treatment and prevention.
Pathogenesis (Gr. genesis – origin) – science of the mechanisms of disease development. This makes it possible, through appropriate treatment, to interrupt the pathogenetic chain in cases where the causative factor is unknown, irremovable or has already started the disease process.
Morphogenesis represents the sequence of local structural changes in the course of a given disease.
Pathognomonic (Gr. gnomos — knowledge) are those morphological changes that are most important and completely sufficient for making the correct diagnosis.
Sanogenesis (lat. sano – heal) studies the mechanisms of healing;
Thanatogenesis (Gr. thanatos – death) studies the cause-and-effect relationships of the disease processes that led to the occurrence of death.
The death of the organism goes through two stages. The first – clinical death, occurs with cessation of breathing, cardiac activity and cessation of reflexes. This stage is reversible within a few minutes, in which vital functions could be restored with intensive resuscitation measures. Recovery time is possible before irreversible changes have occurred in brain tissue, which is most sensitive to lack of oxygen. This period is 7-10 minutes, but in cold weather it can reach 15-20 minutes, because the metabolism slows down when the temperature drops. After this stage, biological death occurs. It is manifested by early death changes, which are sure signs of death. These are: post mortem staining (livor mortis), postmortem cooling (algor mortis) and post mortem rigidity (rigor mortis). Decay is a late postmortem change and its stages are studied by forensic medicine.
Post mortem staining (livor mortis) are a bluish-violet discoloration of the skin in the low-lying parts of the corpse. They are caused by the blood flowing downwards, in the subcutaneous tissue, under the force of the earth’s gravity. Post-mortem marks are absent on the parts of the body where the corpse comes into contact with a hard surface. Once formed, cadaveric spots do not change their location, due to destruction of the walls of small blood vessels and impregnation of tissues with blood.
Post mortem cooling (algor mortis) is a gradual lowering of the corpse’s temperature, which continues until it equals that of the environment. At an air temperature of about 20 degrees and optimal humidity, postmortem cooling progresses at about 1 degree Celsius per hour. This allows, when measuring the temperature of the corpse, an approximate orientation for the time of death. In very cold weather, cooling occurs faster. This mark is checked with the back of the palm placed on the skin of the carcass.
Post mortem rigidity (rigor mortis) is a hardening of the skeletal muscles, which makes it extremely difficult to perform passive movements of the limbs. The hardening of the muscles is so pronounced that if it is necessary to forcibly open the mouth of the deceased, it can also lead to broken teeth. The test is done by trying to bend and unbend a limb. The special thing is that, once forcibly overcome, the stiffness does not develop again, due to the breaking of the connections between the actin and myosin of the muscle fibers.
These three main signs of biological death begin to appear within an hour, an hour and a half after the occurrence of death, and by the fourth hour are already clearly visible.
Methods of pathology
Autopsy (dissection) The pathological autopsy is performed after the signs of biological death appear (after the 4th hour). Its object is non-violent death (as opposed to forensic autopsy). In pathology, patients who died in hospitals are autopsied.
The aims and objectives of the autopsy are:
– training of students and specialists
– establishing the cause of death
– diagnosis of all diseases of the deceased
– study of rare or newly discovered diseases
– control of diagnostic work in the clinic
– control of the healing process
After performing the autopsy, the macroscopic changes are applied to organs and systems in an autopsy protocol. It also describes the results of the microscopic examination of various tissues taken during an autopsy (necropsy). Finally, according to the morphological changes and clinical data for the patient, the final patho-anatomical diagnosis and epicrisis is formed. Discrepancies with clinical diagnosis and reasons for gaps in diagnosis and treatment are reported. Discrepancies regarding the underlying disease or the immediate cause of death, as well as other interesting cases (lat. casus – case), are discussed in a collegial atmosphere. Thus, pathology also realized its last task, which is written as a motto above the doors of the section rooms:
Gefrir – the express histological examination during operative intervention. It is performed on sections prepared with a freezing microtome (German: „gefrieren machen“ – to freeze). The answer is given within 20 minutes, by phone, to the surgeon in the operating room. Depending on the diagnosis, the surgeon determines the volume of the operation.
Biopsy (Greek „bios” – life; „opsis” vision) is a microscopic diagnosis during life of surgically excised tissues or puncture and endoscopic materials (from bone marrow, liver, kidney, lung, myocardium, stomach, intestine, etc.). The treatment of a number of processes, especially tumors, cannot be started without a histological examination. The submitted material must be accompanied by a detailed biopsy slip with guiding clinical data and a description of the operative finding. It is inadmissible for the material to be divided by the surgeon and sent to several laboratories. Thus, conflicting answers will be obtained, since non-uniform parts of the object will be examined. After detailed macroscopic description, the materials were shaped into cubes of approximately 1 cm side to allow the formalin fixative to completely absorb the tissue for 24 h before autolytic changes occurred.
Types of biopsies:
The excisional biopsy (lat. exido — cut out completely) should be taken by cutting out the whole pathological process.
Incisional biopsy – only part of the pathological process is cut out.
Thick needle biopsy – the material is taken with a thick needle from dense parenchymal organs – liver, prostate, kidneys.
Fine needle aspiration – thyroid gland
Gastroenterological biopsy – from the mucous membranes of the stomach, small and large intestines
Punch – biopsy – in dermatology.
Cytological (cellular) diagnostics – gynecological smears or prints from tissue sections. Cytological examination is also performed on various body fluids – urine, pleural effusions, ascites fluid.
Experimental pathology studies diseases reproduced in experimental animals and follows the morphological changes during their treatment.
Pathology uses all methods of normal morphology: light and electron microscopy, histochemistry, immunohistochemistry, immunofluorescence, phase contrast, cytophotometry, autoradiography, morphometry, etc.
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