Introduction to Histology and Cell Structure

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Questions and Answers

What does the term 'Histology' specifically refer to?

The study of tissues (correct)

The study of organisms

The study of organs

The study of cells

Which microscopy technique offers the highest magnification power?

Fluorescence microscopy

Transmission electron microscopy (correct)

Light microscopy

Confocal microscopy

What is the primary purpose of the fixation process in histology?

To enhance the color of tissues

To prepare tissues for freezing

To conduct microscopic analysis

To preserve tissues in a life-like state (correct)

Which of the following is NOT a basic preparation technique of histological sections?

Transfection Signup and view all the answers

What is a primary tissue type specialized for conducting nerve impulses?

Nervous tissue Signup and view all the answers

What is the primary purpose of dehydration in tissue processing?

To remove water from the sample for paraffin impregnation Signup and view all the answers

During the clearing process, which agent is primarily used?

Xylene Signup and view all the answers

What is the purpose of sectioning in tissue preparation?

To cut the sample into thin slices for examination Signup and view all the answers

What is the most commonly used stain for routine histological examination?

Hematoxylin and Eosin (H & E) Signup and view all the answers

What is the result of embedding tissue in hard paraffin?

A hard block of paraffin wax containing the tissue is formed Signup and view all the answers

What is the most commonly used basic staining technique in histology?

Hematoxylin - eosin Signup and view all the answers

What color does hematoxylin typically stain the nuclei of cells?

Blue Signup and view all the answers

Which of the following structures is most likely to be basophilic?

Ribosomes Signup and view all the answers

What is the main purpose of using xylene in tissue processing?

Clearing the tissue Signup and view all the answers

During histological processing, what agent is typically used to remove water from tissues?

Xylene Signup and view all the answers

What is the role of a mounting medium in microscopy?

To protect and support the sample Signup and view all the answers

What is the main component stained by Sudan black dye?

Lipids Signup and view all the answers

Which embedding medium is most commonly used in histology?

Paraffin Signup and view all the answers

Study Notes

Histology Introduction

Histology is the study of tissues
The name "Histology" comes from Greek words "Histos" (tissue) and "logos" (study of)
Histology studies the microscopic structure of cells and organs
Histology is used to correlate structure to function, and understand pathologies of diseases
Histology uses thin slices of tissue viewed under light or electron microscopes.
This is sometimes enhanced by histological stains

Levels of Organization

The levels of organization in the body are organized in a hierarchy
Cell → Tissue → Organ → System

Cell Components

Cytosol
Organelles
Inclusions
Cytoskeleton
Cell Membrane

Tissues

Tissues are groups of similar, specialized cells designed to perform a particular function.
Tissue types include: Epithelial, Connective, Muscle, Nervous

Microtechniques

Microtechniques prepare tissue to study them microscopically
Methods include paraffin method and freezing
Basic techniques include fixation, dehydration, clearing, infiltration, embedding, cutting/sectioning, staining, and mounting.

Fixation

Fixation preserves tissues to "life-like" state
Prevents autolysis and putrefaction
Simple fixatives: formaldehyde, alcohol, acetic acid, osmic acid, and picric acid
Complex fixatives: Bouin's fluid, Zenker's fluid, and special mixtures
10% formaldehyde is the cheapest and easiest.

Dehydration

Dehydration aims to remove water for paraffin impregnation
Done by increasing alcohol concentrations
Prevents tissue shrinkage

Clearing

Clearing removes alcohol and allows paraffin to permeate the tissue.
The tissue is immersed in xylene (xylol) which is miscible with both dehydration and embedding mediums
The process is named for the resulting clear tissue appearance

Infiltration

Infiltration (impregnation with paraffin) immerses the specimen in a medium for easy cutting
Melted paraffin penetrates the tissue and replaces xylene
Usually takes 15 minutes in the oven

Embedding

Embedding in hard paraffin involves placing the tissue in a mould with melted paraffin, then allowing it to solidify
Forms a hard paraffin block of wax that contains the tissue

Sectioning

Sectioning cuts the paraffin block into thin slices (4-10 µm)
This is done with a microtome to prepare for microscopic viewing
Tissue sections are then transferred to glass slides

Staining

Staining adds color to tissue structures, enabling differentiation
Numerous different staining procedures exist
Hematoxylin and eosin (H&E) is the most common stain
H&E stains nuclei blue and cytoplasm pink

Hematoxylin and Eosin (H&E)

H&E stains are commonly used in routine histological examination of tissue.
Hematoxylin is used as a basic dye that stains acidic components of cells blue.
Eosin is used as an acidic dye that stains basic components of cells reddish-pink
Commonly used across tissue specimens

Other Staining Techniques

Periodic acid-Schiff (PAS) stains polysaccharides (e.g., glycogen)
Masson's Trichrome stains collagen
Sudan black and Oil Red stains lipids

Mounting

Mounting places a protective medium on the tissue specimen
Refractive index of the mounting medium should be similar to the glass
This is done to allow for microscopic viewing while protecting the slide

Microscopy

Light Microscopy has a maximum magnification of x1000
Electron Microscopy has a maximum magnification of x1,000,000

Embedding Medium

Paraffin is the most common embedding medium

Section Thickness

Typical section thickness for light microscopy is 4-10 μm

Additional Information

Tissue Processing Steps for FFPE Samples
Questions regarding the above topics and processes

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Description

This quiz covers the fundamentals of histology, including the structure and organization of tissues and cells. Learn about the levels of organization in the body and the techniques used to prepare tissues for microscopic study. Perfect for students beginning their journey into the study of tissues and cells.