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MindMap Gallery Introduction to Histology

Introduction to Histology

Histology and Embryology, summarizes the research content and significance, The development history of histology, common technical methods of histology, etc. Hope this mind map helps you!

Edited at 2024-02-08 17:05:18

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Introduction to Histology

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Outline

Histology and Embryology-Circulatory System
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- 1
- 1
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Histology and Embryology-Digestive Glands
- 81
- 2
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Mind map of the four basic tissues of histology and embryology
- 65
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epithelial tissue
- 38
- 1
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Embryonic Embryonic Chapter 6 Muscle Tissue
- 84
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Embryonics Chapter 4 Blood
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Introduction to Histology

Research content and significance

definition

A discipline that studies the microstructure of the normal human body and its related functions

research content

cell

The basic unit of body structure and function

organize

It is an organic combination of cells and extracellular matrix with similar morphological structures and similar physiological functions.

type

epithelial tissue

connective tissue

muscle tissue

nervous tissue

organ

It is composed of different types of basic tissues and has certain morphological structure and physiological functions.

system

It is an organic combination of several organs with different morphological structures and similar physiological functions, which can complete a certain continuous physiological function.

type

nerve

cycle

immunity

endocrine

Feel

Digestion

breathe

Urology

reproduction

significance

Morphological structure determines physiological function, and morphological structure is the basis of physiological function.

History of Histology

British scholar Hooke discovered the "cell"

British scholar Bixia proposed "organization tissue"

German scholar Meyer proposed "histology biology"

German scholars Schleiden and Schwan established the "cell theory"

German scholar Virchow proposed the "cytopathology theory"

The electron transmission microscope was introduced in 1932

Commonly used technical methods in histology

General light microscopy (LM)

Referred to as a light microscope, it can magnify objects 1000~1500 times with a resolution limit of 0.2μm.

specimen preparation method

slice method

paraffin sectioning

1) Material extraction: The thickness should not exceed 0.5cm, and the tissues and organs obtained from the material are called tissue blocks.

2) Fixation: In order to prevent the protein in the tissue block from decomposing and autolyzing, and to maintain the morphological structure of the cells during life, they need to be fixed with a fixative. Commonly used fixatives include formaldehyde, ethanol, acetone or mixed fixatives.

3) Dehydration: The purpose is to make the embedding agent easily immersed in the tissue block. The commonly used dehydrating agent is ethanol. Gradient dehydration prevents excessive water loss and affects normal morphology

4) Transparency: Use xylene, benzene, and chloroform to soak the tissues and organs to replace the ethanol.

5) Embedding: In order to increase the hardness of the tissue block and facilitate cutting into thin sections, paraffin, collodion, resin and other materials are commonly used for embedding.

6) Slicing: Use a microtome to cut the tissue block into thin slices with a thickness of 5~10 μm, and mount them on a glass slide.

7) Dewaxing: The process of removing paraffin components from paraffin sections through xylene is called dewaxing. Its purpose is to facilitate the coloring of dyes during dyeing.

8) Dyeing:

Principle: Based on the principle that the dye and tissue cells can chemically combine or physically adsorb, the different component structures of the tissue cells form a color difference (contrast), which is convenient for observation under a light microscope.

H-E staining (hematoxylin and eosin staining) Chromosomes and ribosomes are stained with hematoxylin and appear purple-blue; The cytoplasm and extracellular matrix are stained pink with eosin.

9) Sealing the slide: add drops of neutral gum and cover it with a coverslip. This is called a paraffin section specimen and can be observed under a light microscope.

cryosection

The extracted tissue blocks do not undergo steps such as fixation and embedding, but are directly frozen quickly and then sliced in a cryostat microtome.

Advantages: It can effectively preserve lipid components and enzyme activities in tissues and organs, and is often used in cell histochemistry research.

non-slicing method

Refers to the method of making slices without steps such as embedding and slicing.

Smear: directly apply blood, semen, isolated cells, exfoliated cells, etc. on a glass slide

Spreading: tear the mesentery and subcutaneous tissue into thin slices and lay them directly on the glass slide

Grinding: Mechanically grind hard tissues and organs such as teeth and bones into thin slices and attach them to a glass slide.

Special optical microscopy technology

Fluorescence microscopy technology, inverted microscopy technology, phase contrast microscopy technology, dark field microscopy technology, laser confocal microscopy technology

Electron Microscopy (EM)

Principle: The electron beam (electron gun) is used instead of the light source, and the electromagnetic lens is used instead of the condenser, eyepiece, and objective lens. The electron beam produces different short wavelengths under different voltages. Therefore, the resolution limit of the electron microscope is 0.1~0.2nm, which can magnify the object by nearly 100 nm. Ten thousand times.

Commonly used techniques

Transmission electron microscopy

Sample preparation: 1 mm × 1 mm × 1 mm tissue is fixed with glutaraldehyde or osmic acid, embedded in resin, and made into 50~100 nm ultrathin sections using an ultramicrotome, mounted on a copper grid, and covered with lead and uranium. After the heavy metal salt is electron stained, it is observed under an electron microscope.

Any part that is electron-stained and bound by heavy metal salts has a darker image and is said to have high electron density. On the contrary, if the image is brighter, it is said that the electron density is low.

The staining method that combines the detected structure with heavy metal salts is called positive staining. The staining method when the heavy metal salt does not bind to the structure to be examined but binds to the area around the structure to be examined is called negative staining.

Scanning electron microscope technology, freeze etching replica technology, freeze cutting technology, scanning electron microscope casting technology, X-diffraction microanalysis technology, ultra-high voltage electron microscope technology, scanning probe electron microscope technology

Histochemistry and Cytochemistry Techniques

Principle: Based on the principles of physical and chemical reactions, certain chemical substances to be detected in tissue cells form colored precipitates, which facilitates qualitative, localization and quantitative research on them under a light microscope or electron microscope.

research content

1. Sugar

It is shown that polysaccharides and proteoglycans are commonly used in periodic acid-Schiff reaction, referred to as PAS reaction.

Principle: The periodic acid oxidation reaction can oxidize the ethylene glycol group of the sugar molecule to form a glyoxal group. The latter is combined with the colorless basic fuchsin in the Schiff reagent to form a purple-red reaction at the site where the original sugar molecule exists. The product forms a precipitate, indirectly showing the status of intracellular sugar substances.

2. Lipids (including fats and lipids)

In order to prevent organic solvents from dissolving it, frozen sections are often used.

Sudan black, Oil Red O, Nile Blue and other lipid-soluble dyes can be used for dyeing; Osmic acid fixation and dyeing can also be used. Fatty acid or choline treatment can reduce osmic acid to OsO₂, making the lipids appear black.

3. Enzyme

The basic principle is to use an enzyme to hydrolyze and oxidize its corresponding substrate. When the reactant produced by the enzyme reacts with the capture agent, a colored product can be formed. The intensity of the color of the final product is often used to indicate the strength of the enzyme activity.

4. Nucleic acid

Fulgen reaction reveals DNA Principle: The bond between deoxyribose and purine in DNA is opened after treatment with dilute hydrochloric acid. After forming an aldehyde group, it reacts with the basic fuchsin in Schiff reagent to make the DNA purple-red.

Methyl green-pyronine (pyro red) reaction Can make DNA appear blue-green and RNA appear red at the same time

Immunohistochemistry and immunocytochemistry technology, in situ hybridization technology, cell stoichiometry technology, autoradiography technology, in vitro culture technology, cell fusion technology, tissue engineering technology

study method

Basophilic structure

Nucleus, rough endoplasmic reticulum, free ribosomes

dye

Commonly used acid dyes: eosin, fast green, orange G, etc.

Commonly used alkaline dyes: hematoxylin, methylene blue, basic fuchsin, etc.