Histologi

Histologi is the branch of biology and medicine that studies the microscopic structure of tissues. It describes how cells organize into tissues and how that organization relates to function in organs and systems.

Histology covers the four basic tissue types: epithelium, connective tissue, muscle, and nervous tissue, and examines their organization, development, and interactions within organs.

Preparation and staining: To observe tissues, specimens are fixed to preserve structure, embedded in paraffin or resin, sectioned into thin slices, mounted on slides, and stained. The most common stain is hematoxylin–eosin (H&E), which contrasts nuclei and cytoplasm. Additional stains and techniques, such as Masson's trichrome, Periodic acid–Schiff (PAS), and specialized stains, highlight connective tissue, carbohydrates, and other components.

Microscopy and techniques: Light microscopy is standard; electron microscopy reveals ultrastructure; modern methods include immunohistochemistry, immunofluorescence, and in situ hybridization to detect proteins and nucleic acids. Fluorescence and confocal microscopy enable detailed three-dimensional imaging.

Applications and relation to pathology: Histology is essential in basic research and medical education, and forms the foundation of histopathology, the examination of tissue for disease. It is distinct from cytology, which studies individual cells, and from gross anatomy, which involves macroscopic structures.

History: The discipline developed in the 19th century with advances in microscopy and tissue processing.