In histology, doctors use technical aids such as a light microscope to identify the structure of different structures.

Microscopic anatomy divides the organs according to their components, which become increasingly smaller the deeper the examinations go into the different structures. The areas of early diagnosis, pathology , anatomy and biology are mainly concerned with this medical field.

Treatments & Therapies

The microscopic anatomy divides the organs into three groups according to their size and components. Histology as the study of human tissue is a major part of biology, medicine, anatomy and pathology.Cytology 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, also known as particles. The main task of histology is the early diagnosis of tumors . Using the finest examination methods, the physicians find out whether there are pathological changes, i.e. malignant tumors, or whether the tissue is still healthy and the tumors are benign. Furthermore, the histologists are able to detect bacterial, parasitic and inflammatory diseases as well as metabolic diseases .

The histology also forms the starting point for later therapeutic approaches that are based on the histological findings. Histologists and pathologists use histology to “make small things big or visible”. Part of the diseased tissue is removed from the patient in a test excision (biopsy). This tissue sample is then examined by a pathologist by making micrometer-thin cutting patterns. In the next step, these patterns are colored and viewed under the light microscope. Sometimes a high-resolution electron microscope is also used, but this is mainly used in research. Before the examination, the histology deals with how the tissue is processed. A medical technical assistant (MTA) is responsible for this step. He fixes the tissue

The assistant examines the cut fabric macroscopically (with the eye), dehydrates and impregnates it in liquid paraffin. The tissue sample is then blocked in paraffin and in the next step a section with a diameter of 2 to 5 µm is made. This is attached to the glass slide and stained. The routine state of the art is the production 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 to the last step. A less time-consuming tissue examination is frozen section examination. This is always done when the surgeon needs timely information about the removed tissue during an operation.

If the surgeon removes a tumor from the kidney , for example, he needs information about the condition of the tissue during the operation. He needs to know whether the tumor has already been completely removed or whether malignant tissue on the edges indicates further pathological changes. The findings of the frozen section examination decide on the further course of the operation. The tissue sample is frozen and stabilized at -20°C within ten minutes. A 5 to 10 µm section is made using a microtome, attached to a glass plate as a slide and stained. The findings are immediately forwarded to the operating room so that the surgeon is able to make a decision about the further course of the operation.

Diagnosis & examination methods

The most important technical aids in histology are the various staining methods. The histology classifies the cell structures according to their color reaction to the dye used. These are biological colorings. Neutrophil cell structures are not stained by either acidic or basic dyes.The components are lipophilic. Basophil cell structures work with basic dyes such as hematoxylin. Acidophilic cell structures stain with 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. The hematoxylin-eosin stain (HE stain) is most commonly used as a routine and overview stain by computer-controlled automatic stainers. At the same time, manual special stains are used for individual questions.

Histochemical investigations present a complex picture of chemical-physical processes with regard to electroadsorption, diffusion (distribution) and interfacial adsorption in connection with the charge distributions within the dye molecules. Ionic bonding creates the main binding force by binding acidic dyes to basic proteins. In histochemical processes, a dye reacts to a tissue component. Enzyme histochemical methods cause color development through the activity of the cell’s own enzymes . Since the 1980s, classical histology has been supplemented by immunohistochemistry. This assigns the cell properties on the basis of an antigen – antibody-Reaction after. This is made visible using a multi-section technique based on the color reaction at the site of the antigen ( protein ).

A decade later, in situ hybridization was invented. Certain nucleotide sequences are detected by melting double-stranded DNA and spontaneous docking of single strands using RNA or DNA. The nucleic acid sequences are displayed using fluorochrome-labeled probes. This method is called fluorescence in situ hybridization (FISH).

Important staining methods are the azane stain, Prussian blue reaction, Golgi stain, Gram stain and Giemsa stain. 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 differential blood cell staining.