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HISTOLOGY & EMBRYOLOGY Teaching PPT Dept. of Anat., Hist. & Embry. School of Medicine Xi’an Jiaotong University


Qiu Shudong HIS TOLOGY

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INTRODUCTION Definition : A science: study normal micro-structure & its related function of human body. 4 structural levels : Cell : the smallest structural & functional unit. Tissue : groups of cells (similar in morphology or related in function)+ intercellular materials 4 types of fundamental tissue epithelium connective tissue muscular tissue nervous tissue


Organs : organizations of various kinds of tissues in particular ways & perform a specific function. System : formed by several function-related organs which together perform a continuous physiological function. For example: digestive system

Why to study histology ?:

Why to study histology ? To complete the knowledge of human body’s structures----from gross to microscopic Be able to understand how the different tissues function----the basis of physiology Can find the diseases only after the normal is known----the basis of pathology It is related to some modern science fields: cell apoptosis, cell recognition, implantation of embryo stem cells, eugenics and etc. It is also a foundation of clinic sciences—for a good doctor needed in futrue

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Unit used in microscope 1μm=1/1000 mm 1 n m=1/1000μm Maximum resolution Light microscope: 0.2μm Transmission electron microscope: 0.2nm Scanning electron microscope: 5 nm

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Investigative methods of histology I. L ight microscopy


l 1. Tissue p reparation A. paraffin section preparation Specimen: as fresh as possible Fixation: fixative: formalin solution; purpose: to preserve the structural organisation Dehydration: replace the water in the tissue by alcohol C learing: replace the alcohol by xylene E mbedding: replace the xylene w/ melted paraffin Sectioning & mounting

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B. Frozen section: Better for preserving chemical components (e.g. enzymes) Freezing → cryotomy →s taining C. the others: Smear preparations: for blood etc; Grind preparations: for bone


2. Staining Purpose: To make tissue section pigment for observation. H-E Staining: Hematoxylin : basic dye, purple-blue Eosin : acid dye, pink color B asophilic : components bonded by basic dye (H); pruple-blue(nuclear chromatin & basophilic substance in cytoplasm) Acidophilic : components bonded by acidic dye (E); pink (cytoplasm & collagenous fiber)

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Neutrophilic: do not stain w/ both basic and acid dyes Metachromasia: a dye stains tissue a different color from that of dye solution, e.g. toluidine blue stains mast cells in purple color Special staining: Argyrophilia Fluorescent staining

HO (Hoechst 33258)-PI staining shows the apoptosis in human HL-60 cells:

HO (Hoechst 33258)-PI staining shows the apoptosis in human HL-60 cells Silver staining of the neuron and the bile canaliculi

II. Electron Microscopy:

1. Transmission Electron Microscope (TEM) Using a beam of electrons (short wave-lengths) instead of visible light. S ection preparation: similar to those for L.M mainly, plastic instead of paraffin, 50-70nm thick, heavy metal salts instead of HE. Resolution : 0.1-0.5 nm (0.2nm) Ultrastructrue: The structure in EM Electron-dense / electron-lucent II. Electron Microscopy

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Transmission E lectron Microscope

Diagrams of TEM:

Diagrams of TEM

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2. Scanning Electron Microscope (SEM) Sowing the 3 dimensional surface Architecture of cells and tissues Resolution: 5 nm

III. Histochemistry & Cytochemistry:

III. Histochemistry & Cytochemistry R eveal the chemical composition in situ (e.g. proteins, a.a., nucleic acid, lipids, enzymes etc.) w/ chemical, biochemical methods. The product of chemical reaction should be insoluble / colored / electron- scattering, & be seen in LM or EM

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polysaccharide + HIO 4 (hydroxyl group) (oxidise) Aldehyde group + Shiff’s reagent (colorless) Purplish red depositor For instance : PAS ( P eriodic Acid Schiff) reaction: for manifesting polysaccharide and proteoglycan (e.g. glycogen).

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PAS reaction in the hepatocytes


Immunocytochemistry Based on antigen binds to specific antibody. Tissue section w/ Antigen + labelled antibody labelled Ag-Ab complex Fluoresceinlabelling enzyme labelling colloidal gold labelling

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NOS positive neuron in hypothalamus of rat NOS & GnRH positive Neurons in hypothalamus of rat

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m-ATPase activity in skeletal muscles

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IV. tissue culture V. isotopic tracing VI. in situ hybridization (ISH) — nucleic acid molecular hybridization Use nucleotide probe to check target fragment of intracellular DNA or mRNA in situ, in order to study the g ene expression.

Expression of PSA and PSAmRNA in human prostate (histochemistry & ISH):

Expression of PSA and PSAmRNA in human prostate (histochemistry & ISH)

The method in learning histology:

The method in learning histology Combination of the 2 dimentional structure with 3 dimentional

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Combination of the theory with practice Combination of the structure with function Concern the dynamic change

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