Histology is the study of human tissue. This term is composed of two terms from the Greek and Latin languages. “Histos” in Greek means “tissue” and “logos” in Latin means “teaching”.
What is histology?
Histology is the study of human tissue. In histology, medical professionals use technical tools such as a light microscope to see the structure of different structures. In histology, physicians use technical tools such as a light microscope to recognize the structure of different structures. Microscopic anatomy divides organs in terms of their components, which become progressively smaller as the examinations go deeper into the different structures. Mainly the fields of early diagnosis, pathology, anatomy and biology deal with this medical specialty.
Treatments and therapies
Microscopic anatomy divides organs into three groups in terms of their size and components. Histology, as the study of human tissue, is a major component of biology, medicine, anatomy and pathology. Cytology already goes deeper into the human tissue layers and deals with cell theory and functional composition. Molecular biology is devoted to the smallest components of human cells, the molecules, which are also called particles. The main task of histology is the early diagnosis of tumors. Using the finest examination methods, the physicians find out whether the changes are pathological, i.e. malignant tumors, or whether the tissue is still healthy and the tumors are benign. Furthermore, histologists are able to detect bacterial, parasitic and inflammatory diseases as well as metabolic disorders. Tissue diagnosis also forms the starting point for subsequent therapeutic approaches based on the histological findings. Histologists and pathologists use histology to make “small things big or visible.” A part of the diseased tissue is removed from the patient with a sample excision (biopsy). A pathologist then examines this tissue sample by making micrometer-thin sectional patterns. In the next step, these samples are stained and viewed under a light microscope. Sometimes a high-resolution electron microscope is also used, but this is mainly used in research. Histotechnics deals with how the tissue is processed before the examination. A medical technical assistant (MTA) is responsible for this step. He fixes the tissue in order to achieve stabilization. The assistant looks at the cut tissue macroscopically (by eye), dehydrates and impregnates it in liquid kerosene. The tissue sample is then blocked in kerosene and the next step is to make a section of 2 to 5 µm in diameter. This is attached to the glass slide and stained. The routine state of the art is the preparation of an FFBE preparation, a “formalin-fixed paraffin-embedded tissue”. The tissue sample is stained in a hematoxylin-eosin. This process takes one to two days from the first step to the last. A less time-consuming tissue examination is the frozen section examination. This is done whenever the surgeon needs timely information about the removed tissue during surgery. For example, if the surgeon removes a tumor from the kidney, he needs information about the nature of the tissue while the operation is still in progress. He needs to know whether the tumor has already been completely removed or whether malignant tissue at the margins indicates further pathological changes. The findings of the frozen section examination determine the further course of the operation. The tissue sample is frozen and stabilized at -20°C within ten minutes. Using a microtome, a 5 to 10 µm section is made, mounted on a glass plate as a microscope slide, and stained. The findings are immediately forwarded to the operating room so that the surgeon is able to make a decision on how to proceed with the operation.
Diagnosis and examination methods
The main technical tools of histology are the various staining methods. Histology classifies cell structures according to their color response to the dye used. These are biological staining methods.Neutrophil cell structures are not stained by either acid or basic dyes. The components are lipophilic. Basophilic cell structures work with basic dyes such as hematoxylin. Acidophilic cell structures stain by basic and acidic dyes such as eosin, acid fuchsin, and picric acid. Other cell structures are nucleophilic and argyrophilic. Argyrophilic cell structures bind silver ions, nucleophilic DNA-binding and basic dyes. Hematoxylin-eosin staining (HE staining) is most commonly used as routine and survey staining by computer-controlled automatic staining machines. In parallel, manual special stains are used for individual questions. Histochemical studies present a complex picture of chemical-physical processes with respect to electroadsorption, diffusion (distribution) and interfacial adsorption in connection with the charge distributions within the dye molecules. Ion bonding generates the main binding force by binding acidic dyes to basic proteins. In histochemical processes, a dye reacts to a tissue constituent. Enzyme histochemical methods cause color development through the activity of cellular enzymes. Since the 1980s, classical histochemistry has been supplemented by immunohistochemistry. This detects cell properties on the basis of an antigen-antibody reaction. This is visualized by a multi-slice technique based on the color reaction at the site of the antigen (protein). A decade later, in situ hybridization was invented. Specific nucleotide sequences are detected by the fusion of double-stranded DNA and spontaneous docking of single strands using RNA or DNA. The nucleic acid sequences are visualized using probes with fluorochrome labeling. This method is called fluorescence in situ hybridization (FISH). Important staining methods include azane staining, Berliner blue reaction, Golgi staining, Gram staining, and Giemsa staining. These staining methods work with red cell nuclei, reddish cytoplasm, blue reticular fibers and collagens, red muscle fibers, detection of “trivalent iron ions,” silvering of individual ions, bacterial differentiation, and differentiating blood cell staining.
