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Medical Laboratory Science · 400 Level
This is the complete lecture note for MLS 512 Medical laboratory histopathology, prepared for Medical Laboratory Science students at 400 Level. You can read it online below, open it in the full viewer, or download the PDF for offline study. It pairs with the course's video lectures, so you can read and watch together.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course code: MLS 512 Course title: Medical Laboratory Histopathology Course credit load: 2 Units Series 1: Theory And Methodology Of Histochemistry • Part 1.1: Fundamentals Of Histochemistry • Sub-Part 1.1.1: Definition and scope of histochemistry • Sub-Part 1.1.2: Principles and methodology of histochemical techniques • Sub-Part 1.1.3: Applications of histochemistry in medical laboratory practice • Part 1.2: Histochemical Techniques For Specific Tissues • Sub-Part 1.2.1: Chromaffin tissues and their staining methods • Sub-Part 1.2.2: Schmorl’s technique and its diagnostic use • Sub-Part 1.2.3: Diazo reaction and its applications • Sub-Part 1.2.4: Perls’ Prussian blue reaction for iron detection • Part 1.3: Methodological Considerations And Case Applications • Sub-Part 1.3.1: Technical limitations and challenges in histochemistry • Sub-Part 1.3.2: Case examples demonstrating histochemical diagnosis • Sub-Part 1.3.3: Integration of histochemistry with other laboratory methods Introduction Histochemistry is a cornerstone of histopathology, providing powerful techniques for visualising chemical components within tissues. By applying specific stains and reactions, histochemistry allows us to detect substances such as enzymes, lipids, and pigments directly in situ. This makes it an essential tool for diagnosis and research, as it bridges the gap between microscopic structure and biochemical function. In this Series, you will be introduced to the theory and methodology of histochemistry, preparing you to appreciate its role in medical laboratory practice. The aim of this Series is to equip you with the knowledge and skills to define the principles of histochemistry, describe its methodology, and analyse the diagnostic applications of selected histochemical techniques.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS We shall commence this Series by exploring the fundamentals of histochemistry, including its definition, scope, and applications. Next, we will move on to specific histochemical techniques, such as those used for chromaffin tissues, Schmorl’s method, the diazo reaction, and Perls’ Prussian blue reaction. Finally, we will wrap up by considering methodological challenges and case applications, showing how histochemistry integrates with other laboratory methods to support accurate diagnosis. Series Learning Outcomes Upon completing this Series, you should be able to: • SLO 1.1 define the principles and scope of histochemistry in medical laboratory practice, • SLO 1.2 explain the methodology of histochemical techniques and their applications, • SLO 1.3 describe the histochemical procedures used for chromaffin tissues, Schmorl’s method, the diazo reaction, and Perls’ Prussian blue reaction, • SLO 1.4 analyse the diagnostic significance of selected histochemical techniques in tissue studies, • SLO 1.5 evaluate methodological challenges and limitations in histochemistry, and • SLO 1.6 apply knowledge of histochemical procedures to case examples, integrating them with other laboratory methods. 1.1 Fundamentals Of Histochemistry 1.1.1 Definition and scope of histochemistry Histochemistry is the branch of science that combines histology and chemistry to study the chemical composition of cells and tissues. It involves the use of specific stains and reactions to visualise substances such as enzymes, lipids, carbohydrates, and pigments directly within tissue sections. This makes histochemistry a vital tool in medical laboratory practice, as it allows us to link microscopic structures with biochemical functions. Fill in the blank: Histochemistry combines histology and ______ to study the chemical composition of tissues.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.1: Relationship between histology, chemistry, and histochemistry 1.1.2 Principles and methodology of histochemical techniques The principle of histochemistry is based on the chemical reaction between a reagent and a specific tissue component, producing a visible colour change. The methodology involves preparing tissue sections, applying appropriate stains, and observing the results under a microscope. Each technique is designed to highlight a particular substance, such as iron, glycogen, or enzymes, thereby aiding diagnosis. Fill in the blank: The principle of histochemistry is based on a chemical ______ between a reagent and a tissue component. Plate 1.1: Histochemical staining of tissue sections
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 1.1.3 Applications of histochemistry in medical laboratory practice Histochemistry has wide applications in medical laboratory practice. It is used to detect abnormal deposits such as iron in haemochromatosis, glycogen in storage diseases, and enzymes in metabolic disorders. It also helps differentiate between normal and pathological tissues, supporting accurate diagnosis. In research, histochemistry provides insights into cellular function and disease mechanisms. Fill in the blank: Histochemistry can detect abnormal deposits such as ______ in haemochromatosis. Application Key significance Detection of iron in haemochromatosis Identifies abnormal iron deposits in tissues; aids diagnosis of iron overload disorders Identification of glycogen in storage diseases Demonstrates glycogen accumulation in cells; useful in metabolic disease diagnosis Demonstration of enzymes in metabolic disorders Reveals enzyme activity or deficiency; helps in characterising metabolic abnormalities Differentiation of normal and pathological tissues Highlights structural and chemical differences; supports histopathological diagnosis Research into cellular function and disease mechanisms Provides insights into biochemical processes and pathogenesis at the tissue level Box 1.1: Applications of histochemistry in medical laboratory practice Pilot questions 1.1 1. What is histochemistry? 2. Which two sciences are combined in histochemistry? 3. What is the principle of histochemical techniques? 4. Name one abnormal deposit that histochemistry can detect. 5. Mention one application of histochemistry in medical laboratory practice. 1.2 Histochemical Techniques For Specific Tissues 1.2.1 Chromaffin tissues and their staining methods Chromaffin tissues are specialised cells found mainly in the adrenal medulla that store and secrete catecholamines such as adrenaline. They are called chromaffin because they take up chromium salts during staining, producing a characteristic brown colour. This reaction is useful in identifying adrenal medullary tumours and other neuroendocrine lesions. Fill in the blank: Chromaffin tissues are specialised cells that store and secrete ______.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Plate 1.2: Chromaffin tissue staining with chromium salts 1.2.2 Schmorl’s technique and its diagnostic use Schmorl’s technique is a histochemical method used to demonstrate reducing substances such as lipofuscin pigments in tissues. Lipofuscin is a wear-and-tear pigment that accumulates with age or in certain pathological conditions. Schmorl’s stain produces a blue-green colour, making it easy to identify these pigments in tissue sections. Fill in the blank: Schmorl’s technique is used to demonstrate ______ pigments in tissues.
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Figure 1.2: Schmorl’s technique for detecting lipofuscin pigments 1.2.3 Diazo reaction and its applications The diazo reaction is a histochemical technique used to detect aromatic amines and proteins in tissues. It involves coupling reactions that produce coloured azo compounds, which can be visualised under the microscope. This method is particularly useful for demonstrating certain enzymes and protein components in cells. Fill in the blank: The diazo reaction produces coloured ______ compounds that can be visualised under the microscope. Application Key significance Detection of aromatic amines in tissues Identifies specific chemical groups; useful in biochemical and pathological studies Demonstration of protein components Highlights protein structures and distribution in tissues Identification of certain enzymes Reveals enzyme activity/localisation; supports metabolic and functional analysis Box 1.2: Applications of the diazo reaction 1.2.4 Perls’ Prussian blue reaction for iron detection Perls’ Prussian blue reaction is a classic histochemical technique used to detect iron deposits in tissues. The method involves treating tissue sections with hydrochloric acid and potassium
LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS ferrocyanide, which react with ferric iron to produce a blue colour. This technique is widely used in diagnosing conditions such as haemochromatosis and siderosis. Fill in the blank: Perls’ Prussian blue reaction produces a ______ colour when iron deposits are present. Plate 1.3: Perls’ Prussian blue reaction for iron detection Pilot questions 1.2 1. What are chromaffin tissues and what do they secrete? 2. Which pigment is demonstrated by Schmorl’s technique? 3. What type of compounds are produced in the diazo reaction? 4. What colour is produced by Perls’ Prussian blue reaction? 5. Name one condition diagnosed using Perls’ Prussian blue reaction. 1.3 Methodological Considerations And Case Applications 1.3.1 Technical limitations and challenges in histochemistry Although histochemistry is a powerful diagnostic tool, it is not without limitations. One challenge is the specificity of stains, as some reagents may react with multiple tissue components, leading to false positives. Another issue is the preservation of tissue samples, since fixation methods can alter chemical structures and interfere with staining reactions. Furthermore, interpretation requires skill, as subtle differences in colour intensity may carry significant diagnostic meaning.
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