Histology (Gr histo, tissue + logos, study) is the study of the microscopic structure of cells, tissues and the extracellular matrix of tissues and the structural and functional relations between the individual components.
Sub-disciplines include histochemistry, histophysiology, histopathology and immuno-histochemistry, all which help to understand normal and abnormal tissue biology.
Coetzee et al p3-5
Why study histology?
Histology is central to biological and medical sciences since it bridges the gap between physiology, biochemistry, genetics and molecular biology on the one side and disease processes and their effects on the other side.
Studying the arrangement of different tissues at the microscopic level gives insight into the gross structure and function of organs and systems.
Studying the fine structure and molecular organization of cells greatly improves comprehension of biochemical and physiological processes.
Histology is essential for understanding pathology.
Histology is essential for the accurate diagnosis and treatment of cancer. Classification of tumours is determined by histology and accurate histological tumour assessment is the foundation of modern cancer treatment.
Stevens & Lowe p1-4
Chemical level: atoms, ions, molecules
Organelle level: chemical components combine to form organelles like mitochondria, endoplasmic reticulum, etc
Cellular level: organelles are arranged to form cells
Tissue level: a collection of similar cells that are specialized to perform a specific function
Organ level: different kinds of tissues arranged together to perform a special function
System level: various organs organized together to perform a complex function
Wheater's Functional Histology p32
What is a cell?
Cells are the smallest structural units that display the characteristics of life.
Complex aqueous gel made of protein, carbohydrates, fat, nucleic acids and electrolytes
Each cell is surrounded by a membrane that separates it from the environment and from other cells
Cell are divided into specialized functional compartments (organelles) by inner membrane systems
Cytology (Gr kytos, cell + logos) is the study of individual cells
General cell structure is studied with the light microscope
Ultrastructure is studied with electron microscope and reveals fine detail
Coetzee et al p9-12
Wheater's Functional Histology p2-3 (3e Ed) or p4-5 (4e Ed)