Histology

• Histology is the study of the tissues of the body and how these tissues are arranged to constitute organs.
• Histology involves all aspects of tissue biology, with the focus on how cell's structure and arrangement optimize functions specific to each organ.
• Tissues are made up of two interacting components: cells and extracellular matrix.
• Extracellular matrix are highly organized molecules that form complex structures and perform functions such as furnishing mechanical support for the cells, transporting nutrients to the cells, and carrying away catabolites and secretory products.
• The preparation of tissue for study involves the removal of unwanted material and the preservation of the tissue.
• The tissue can then be preserved through a process called embedding, which involves the placement of the tissue in a support material.
• The sections can then be stained and mounted for viewing, a process that enhances the appearance of the tissue.
• The tissue can be sectioned for further study, a process that involves cutting the tissue into thin slices.
• The unwanted material can be removed through a process called fixation, which involves the use of chemicals to stabilize the tissue.
• The support material can be a variety of materials, including plastics, resins, and waxes.
• Histopathology deals with the study of the basic disease process, correlating the etiology of disease with the course development of anatomic and clinical changes brought about by disease.
• Histopathological techniques deal with the preparation of tissues for microscopic examination.
• The aim of histopathological techniques is to produce microscopic preparations of tissues, usually stained, that represent as closely as possible their structures.
• Exfoliative cytology is a branch of science that deals with the study of cells that have been desquamated from epithelial surfaces, originated from exfoliative cells coming from the lining epithelium and mucosa of different organs of the body.
• Cytology is the study of abnormal cells as in cancer cells.
• Cytotechnique is the study of the methods of preparing the cells for microscopic examination.
• Tissues from the body taken for diagnosis of disease processes must be processed in the histology laboratory to produce microscopic slides that are viewed under the microscope by pathologists.
• Hematoxylin stains acidic molecules shades of blue.
• Infiltration is the process where the melted wax penetrates in between the cells of the tissues, a necessary step to harden the tissues before their embedding.
• Trimming is the process of trimming the paraffin block to expose the tissue for sectioning on a microtome.
• Histotechnologies refer to the techniques for processing tissues, whether biopsies, larger specimens removed at surgery, or tissues from autopsy.
• Staining makes the various tissue components conspicuous and to permit distinctions between them.
• H & E stains are universally used for routine histological examination of tissue sections.
• Section cutting is the process of sectioning biological specimens into very thin segments for microscopic examination by means of a mechanical equipment, called the microtome.
• Eosin stains basic materials shades of red, pink and orange.
• Histotechnologists are responsible for fixation, which prevents autolysis and bacterial attack, and fixes the tissues so they will not change their volume and shape during processing.
• Embedding is the process by which tissues are surrounded by a medium such as agar, gelatin, or wax which when solidified will provide sufficient external support during sectioning.
• Histotechnologists are also responsible for dehydration, which removes fixative and water from the tissue and replaces them with dehydrating fluid.
• Clearing is the process of replacing the dehydrating fluid with a fluid that is totally miscible with both the dehydrating fluid and the embedding medium.
• A cell is the basic unit of all living things, including humans.
• Differentiation is the process by which cells of an embryo become specialized structurally to augment specific cytoplasmic activities for functions at the level of tissues and organs.
• Cells metabolize and release energy.
• Cells synthesize molecules.
• Cells provide a means of communication.
• Cells reproduce and provide for inheritance.
• Cytoplasm is a homogenous substance that fills the cell and the various formed elements embedded in it.
• The plasma membrane is the outermost layer of the cell, 7.5 - 10 nm thick, and is a lipid bilayer composed of phospholipids and cholesterol with proteins extending across or are embedded in either surface of the lipid bilayer.
• Apoptosis is the process of cell suicide, a rapid, highly regulated cellular activity that shrinks and eliminates defective and unneeded cells.
• Apoptosis results in small membrane-enclosed apoptotic bodies, which quickly undergo phagocytosis by neighboring cells or cells specialized for debris removal.
• The BCL-2 family is activated by either external signals or irreversible internal damage.