Introduction to Histology Lecture (1) - PDF

INTRODUCTION TO HISTOLOGY ❑ Histology: is the study of the microscopic structure of cells, tissues, and organs. ❑ Tissue: is an aggregate of more or less similar cells, which perform one function or more. ❑Organ: is a collection of tissue sharing one or more functions. ❑ System: is an...

INTRODUCTION TO HISTOLOGY ❑ Histology: is the study of the microscopic structure of cells, tissues, and organs. ❑ Tissue: is an aggregate of more or less similar cells, which perform one function or more. ❑Organ: is a collection of tissue sharing one or more functions. ❑ System: is an association of several organs that perform particular functions such as digestion, circulation, reproduction, and immunity. (digestive, circulatory, reproductive, immune).  These tissues do not exist in the body as isolated units; they are associated together to form the organs of the body.  Origin of tissues 1. Epithelial tissue: derived from any of the three germ layers (ectoderm, mesoderm, and endoderm). 2. Connective tissue: derived from mesoderm. 3. Muscular tissue: derived from mesoderm. 4. Nervous tissue: derived from ectoderm ❖ The resolving power of a microscope is a measure of the capacity of a microscope to separate two points close together. ❖ The resolving power of the light microscope for example is about 0.2 microns.  The most important units of measurement used in histology are : ❑ One centimeter (cm) = 10 millimeters (mm) ❑ One millimeter (mm) = 1000 micrometers (µm) = 1000 microns (µ) ❑ One micrometer (one micron) = 1000 namaometer (nm). ❑ One micrometer (one micron) = 10.000 Angstrom (Ao) ❑ One nanometer (nm) = 10 Angstrom = 10 Ao ❑ One Angstrom (Ao) = 1/10.000 of micron Several types of microscopes are available for the study of biological materials. Major kinds of microscopes 1. Light microscope: utilize light elimination. 2. Electron microscope: utilize electron beam. Light Microscope Transmission Electron Microscope ‫الميكروسكوب االلكتروني النافذ‬  Differences between Light Microscope and Electron Microscope Light Microscope Electron Microscope Illuminating source Light. A beam of electrons. Specimen preparation takes usually few minutes to hours. takes usually takes few days. Specimen type Live or Dead specimens may be seen. Only Dead or Dried specimens are seen. lenses glasses electromagnetic Magnification power 500X to 1500X. 100,000X to 300,000X. thickness of the object 5µm or thicker. 0.1µm or thinner. Air and glass Medium Vacuum is essential for its operation. Vacuum is not required. The specimen is coated with heavy metals to Stain stained by colored dyes reflect electrons. Colored. Black and White. Color of the image Image is seen by eyes through ocular lens. Fluorescent Screen study of detailed gross internal the study of the external surface, ultrastructure of Importance structure. cells and very small organisms.