Introduction To Histology 2024-2025 PDF

Faculty of Applied Health Sciences Technology Course name: Foundation in Health and Disease INTRODUCTION TO HISTOLOGY Dr/ Amel Marzouk Professor of Histology 2024-2025  INTRODUCTION TO HISTOLOGY Learning Objectives:  Identify the micros...

Faculty of Applied Health Sciences Technology Course name: Foundation in Health and Disease INTRODUCTION TO HISTOLOGY Dr/ Amel Marzouk Professor of Histology 2024-2025  INTRODUCTION TO HISTOLOGY Learning Objectives:  Identify the microscope.  Recognize the types of microscopes.  Compare between light & electron microscopes.  Identify the principle of preparation of histology slides for microscopic examination. List the types of tissue sections.  Know the types of staining methods.  What is Histology? Histology is the study of the microscopic structure of cells, tissues and organs of the body. *Tissues have two interacting components: cells and extracellular matrix (ECM). *Because of the small size of cells, the study of histology depends on the use of the microscope.  Microscope Definition: The microscope is an instrument having magnifying lenses for inspecting objects too small to be seen by the human eyes. Functions: 1. Resolution. 2. Magnification.  Resolution *Definition: Resolution is the power of the microscope to distinguish fine details. *Resolution of the microscope depends mainly on the quality of its objective lens. * Resolving power of the human eye is 0.2 mm. * Resolving power of the light microscope (LM) is 0.2 µm. * Resolving power of the electron microscope (EM) is 1 nm.  Magnification Magnification is of value ONLY when accompanied by resolution. Resolving power of LM (0.2µm) allows clear images magnified 1000 times. Resolving power of EM (1 nm) allows clear images magnified 100,000 times.  Let’s Think A B C D A, B, C & D are images of the same object seen by different microscopes. Describe the resolution & magnification of each image?  Types of Microscopes a) Light microscope (LM): is based on the passage of light through thin stained tissue sections. b) Electron microscope (EM): is based on the use of electron beams. There are two main types of EM: 1. Transmission electron microscope (TEM): is based on the passage of electron beams through ultrathin tissue sections to study fine tissue structures. 2. Scanning electron microscope (SEM): The electron beam scans the surfaces of cells, tissues and organs, providing a three dimensional (3D) image. An epithelial tissue examined by LM The same epithelial tissue examined by TEM The same epithelial tissue examined by SEM  Main Differences between LM & EM LM EM Resolving Power 0.2 µm 1 nm Magnification 1000 times 100,000 times Source of Light (have longer Electron Beam (have Illumination wavelength) shorter wavelength) Lenses Glass lenses Magnetic lenses Image of tissue Colored Black and white *Thinstained tissue sections must be prepared for microscopic examination of the tissue.  Main Types of Tissue Sections A) Paraffin sections: It is the most common type of tissue sections for LM. B) Frozen sections: It is a much more rapid processing method for LM. C) Plastic sections: It is used to prepare very thin (=ultrathin) tissue sections for EM. Paraffin section  Staining *Types of staining methods: 1. General staining methods: are used to reveal general structure of the tissue. The most common general stain used is the combination of hematoxylin and eosin (H&E): -Hematoxylin is a blue basic dye which stains acidic cell components such as nucleic acids (DNA & RNA). The cell components stained by basic dyes are called basophilic. -Eosin is a pink acidic dye which stains basic cell components such as most cytoplasm proteins (e.g. mitochondria). The cell components stained by acidic dyes are called acidophilic. The most common general stain used is hematoxylin & eosin (H&E)  Staining (continued) 2. Special staining methods: are used to reveal certain tissue components, e.g. Sudan black dye stains lipids. 3. Histochemical and cytochemical staining methods: are specific chemical staining methods based on binding of the dye with a specific tissue component, e.g. Periodic Acid Schiff (PAS) reaction stains carbohydrates (glycogen). Sudan black dye for staining of lipids PAS reaction for staining of glycogen  Complete: 1. The two interacting tissue components are …………… and …………………. 2. Study of histology depends on the use of ……………….. 3. The two main functions of microscopes are …….……… and ………………….. 4. …………………is the power of the microscope to distinguish fine details. 5. Electron microscopes are based on the use of beam of …………... 6. To study tissues by the microscope, ………………………sections must be prepared. 7. …………….. cell components are stained by acidic dyes. 8. The most common general stain used is …………………………..  Enumerate: 1. Types of microscopes. 2. Types of electron microscope. 3. Functions of the microscope. 4. Types of tissue sections. 5. Types of staining methods. 6. Differences between light and electron microscopes.  Choose the correct answer 1. The electron microscope is characterized by which of the following? a. Glass lens. b. Magnetic lens. c. Colored image. d. Use of light as a source of illumination. 2. In the light microscope, resolution mainly depends on which of the following parts? a. Objective lens. b. Ocular lens. c. Coarse focus. d. Fine focus. 3. For proper light microscopic examination, we use: a. Thick tissue sections. b. Thin stained tissue sections. c. Unstained tissue sections. d. Electron beam. 4. Which of the following are the function of microscope? a. Magnification only. b. Resolution only. c. Magnification and resolution. d. Magnification and staining. Choose the correct answer: 5. Which of the following is used to stain glycogen? a. Silver stain. b. Periodic acid-Schiff reaction. c. Sudan black dye. d. Iron hematoxylin stain. 6. Which of the following is the resolving power of light microscope? a. 1 nm. b. 1 mm. c. 0.2 µm. d. 0.2 mm. 7. Which of the following is a special staining method? a. Hematoxylin. b. Eosin. c. Sudan black. d. Hematoxylin and eosin. 8. Which of the following is a histochemical staining method? a. Hematoxylin. b. Hematoxylin and eosin. c. Eosin. d. Periodic acid-Schiff reaction.  Match Column A&B Column A Column B 1- Magnification a. Power of microscope to distinguish fine details 2- Resolution b. Provide a 3-D image 3- Scanning electron c. Stains lipids microscope 4- Light microscope d. Is 100,000 times in electron microscope 5- Sudan Black dye e. Stains glycogen 6- PAS reaction f. Has glass lenses  Lecture References - Junqueira's Basic Histology: Text and Atlas 17th Edition. Thank you