Histology and Tissue Preparation

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Questions and Answers

What are the two main components of tissues?

Cells and lymphatic fluid

Cells and blood vessels

Cells and connective tissues

Cells and extracellular matrix (ECM) (correct)

Which macromolecules are primarily found in the extracellular matrix (ECM)?

Nucleic acids

Lipids

Collagen fibrils (correct)

Carbohydrates

What is the purpose of cutting thin sections of tissues for microscopy?

To separate different types of cells

To remove excess fluids from the tissue

To allow light to pass through for examination (correct)

To enhance the color of the tissue

How do cells influence the extracellular matrix (ECM)?

Cells produce the ECM locally (B) Signup and view all the answers

What is the equivalent of one micrometer in millimeters?

0.001 mm (D) Signup and view all the answers

What is the purpose of eosin in microscopy?

To serve as a counterstain (A) Signup and view all the answers

What is necessary for a proper understanding of tissue biology?

Familiarity with scientific methods and tools (D) Signup and view all the answers

Which of the following methods utilizes the hexose rings of polysaccharides for staining?

Periodic acid–Schiff (PAS) reaction (D) Signup and view all the answers

During what stage do cells and matrix become functionally specialized?

During developmental stages (A) Signup and view all the answers

What does the Feulgen reaction specifically stain?

Cell nuclei DNA (B) Signup and view all the answers

What do tissue slices prepared for microscopic examination preserve?

Structural features from the body (C) Signup and view all the answers

What is the main challenge in examining most tissues and organs under light microscopy?

Tissues are too thick for light to penetrate (D) Signup and view all the answers

Which of the following processes is typically used to analyze biopsies during surgery?

Rapid processing method (C) Signup and view all the answers

What is the function of enzyme digestion in the identification process of basophilic material?

To specifically target one substrate (D) Signup and view all the answers

What can be stained distinctly purple using the PAS reaction?

Carbohydrate-rich macromolecules (B) Signup and view all the answers

Which spatial unit is equivalent to one angstrom?

0.1 nm (B) Signup and view all the answers

What is the primary focus of histology?

The arrangement of tissues in organs (D) Signup and view all the answers

Which microscopy technique is most suitable for viewing live cells?

Phase-Contrast Microscopy (D) Signup and view all the answers

What is the primary purpose of embedding fixed tissues?

To provide firm consistency for thin sectioning (B) Signup and view all the answers

What is an advantage of using electron microscopy?

It provides superior resolution compared to light microscopy (B) Signup and view all the answers

Which of the following embedding materials is commonly used for light microscopy?

Paraffin (B) Signup and view all the answers

In which technique are specific molecules visualized through the use of antibodies?

Immunohistochemistry (A) Signup and view all the answers

What is the first step in preparing fixed tissue for embedding?

Dehydrating the tissue (B) Signup and view all the answers

What is the purpose of tissue embedding in histology?

To ensure that tissues maintain their structure for sectioning (D) Signup and view all the answers

How do dyes behave when staining tissues?

They form electrostatic linkages with ionizable radicals (C) Signup and view all the answers

What characteristic is unique to confocal microscopy compared to other light microscopy techniques?

It increases depth of field and optical resolution (C) Signup and view all the answers

What is usually the final ethanol concentration used during the dehydration process of fixed tissues?

100% ethanol (C) Signup and view all the answers

Which microscopy method uses a beam of electrons to create images of fine details?

Scanning Electron Microscopy (C) Signup and view all the answers

What is the role of staining in microscopy?

To make tissue components conspicuous and distinguishable (D) Signup and view all the answers

What is the main function of staining in histology?

To make specific structures in the tissue visible (B) Signup and view all the answers

What is a consequence of using plastic resins for embedding fixed tissues?

They can be adapted for both light and electron microscopy (D) Signup and view all the answers

Which property of dyes is important for their function in staining tissues?

Their selective interaction with tissue components (A) Signup and view all the answers

What staining method highlights cell surface glycoproteins and mucin in the epithelium lining the small intestine?

Periodic acid-Schiff (PAS) (B) Signup and view all the answers

What color do the cell nuclei appear when stained with H&E?

Purple (A) Signup and view all the answers

Which component of the small intestine epithelium primarily secretes mucus?

Goblet cells (D) Signup and view all the answers

How long might it take to prepare a slide from tissue fixation to microscopic observation?

12 hours to 2.5 days (D) Signup and view all the answers

What is the primary purpose of mounting a protective glass coverslip on a slide?

To prevent drying of the sample (B) Signup and view all the answers

In what way are PAS-positive regions characterized in the epithelium?

High content of oligosaccharides and polysaccharides (C) Signup and view all the answers

What magnification factor contributes to the total magnification in microscopy?

Both objective and ocular lenses (A) Signup and view all the answers

How does the PAS reaction affect the staining intensity at the lumen of the small intestine epithelium?

It produces intense staining at the lumen and in goblet cells (B) Signup and view all the answers

Which of the following methods is used to preserve cell structures and make the tissue ready for sectioning in a biopsy?

Rapid freezing in liquid nitrogen (D) Signup and view all the answers

What is the primary reason why frozen sections are preferred for studying lipids?

Frozen sections prevent the degradation of lipids during processing. (D) Signup and view all the answers

What is the primary function of the cryostat in the process described?

To section the frozen tissue (B) Signup and view all the answers

Which of the following is NOT a major benefit of using frozen tissue sections for histochemical studies?

Enhanced staining quality (C) Signup and view all the answers

Why is pretreatment with ribonuclease useful in examining cellular structures?

It reduces cytoplasmic basophilia, highlighting the nucleus. (A) Signup and view all the answers

Which of the following staining techniques is used to visualize lipid-rich structures in cells?

Sudan black staining (B) Signup and view all the answers

What is the primary advantage of using frozen sections for the study of sensitive enzymes?

Frozen sections prevent the degradation of enzymes. (B) Signup and view all the answers

Which of the following is a common technique used to visualize certain ECM fibers and cellular elements in nervous tissue?

Silver impregnation staining (A) Signup and view all the answers

Study Notes

Histology & Its Methods of Study

Histology studies tissues and how they form organs, focusing on cell structure and function optimizing organ function.
Tissues consist of cells and extracellular matrix (ECM).
ECM supports cells and transports nutrients & waste.
Cells influence ECM and vice-versa forming a functional continuum.
Tissue types become specialized during development, forming functional organs.
Histology relies on microscopes and biochemical techniques to analyze small structures.

Preparation of Tissues for Study

Tissue slices (sections) for light microscopy are prepared by:
- Fixation: Preserving structures by cross-linking proteins and inactivating degradative enzymes, typically in chemical solutions like formalin.
- Dehydration: Removing water using increasing concentrations of alcohol, often ending with 100% alcohol.
- Clearing: Removing alcohol with organic solvents miscible with both alcohol and paraffin.
- Infiltration: Replacing the clearing solution with melted paraffin, allowing the tissue to become infiltrated.
- Embedding: Placing the infiltrated tissue in a mold with melted paraffin and letting it solidify.
- Trimming: Exposing the tissue for sectioning on a microtome.
Microtome used to slice paraffin-embedded or resin-embedded tissue for light or electron microscopy respectively.
Electron Microscopy is used for higher magnification and resolution of cellular structures, and requires special fixatives and embedding resins (epoxy) than light microscopy.
Thin sections are placed on microscope slides and stained.

Embedding & Sectioning

Tissues are infiltrated/embedded in a material like paraffin for easier sectioning.
Paraffin is for light microscopy, resins for both electron and light microscopy.
Dehydration removes water using increasing ethanol concentrations.
Clearing removes ethanol with organic solvents miscible with both alcohol and the embedding medium.
Tissue is placed in melted paraffin and solidified (embedded).
Resin embedding avoids heat-related tissue distortion.
Microtome cuts thin sections for microscopy.

Staining

Most cells and ECM are colorless. Staining is essential for visualization and identification.
Dyes bind selectively to different tissue components.
Basic dyes (e.g., Hematoxylin) bind to negatively charged molecules (basophilic).
Acidic dyes (e.g., eosin) bind to positively charged molecules (acidophilic).
H&E staining (Hematoxylin & Eosin) is a common method, with Hematoxylin staining nuclei dark blue/purple and Eosin staining cytoplasm and collagen pink.
PAS reaction stains carbohydrate-rich structures (purple/magenta).
Staining specificity can be increased using enzyme digestion or metal impregnation.

Light Microscopy

Bright-field microscopy uses ordinary light to visualize stained tissue sections.
Optics include a condenser, objective lens, and eyepiece for magnification.
Magnification is determined by multiplying objective and eyepiece powers.
Resolution is the ability to distinguish two points as separate. Light Microscopy has a resolution around 0.2 micrometers. This limits the size of structures that can be visualized.
Virtual microscopy digitizes light microscopy images.

Medical Applications

Biopsies are tissue samples used for diagnostic analysis.
Formalin fixation is used for room temperature analysis.
Frozen tissue sections are used for rapid analysis of sensitive enzymes/molecules and lipid rich tissues.
Cryostat is a type of microtome used for frozen tissue sections.

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Description

This quiz covers the fundamentals of histology, including tissue structure, cellular components, and techniques for preparing tissues for microscopic study. You'll learn about the steps involved in the preparation of tissue samples and the significance of cell-extracellular matrix interactions in organ function.