U1 FCFC

What is Histology?

The study of the microscopic anatomy of cells and tissues of humans, animals, and plants.

What is Histopathology?

The microscopic study of diseased tissue.

What are Tissues

Assemblages of similarly specialized cells united in performing a specific function.

Cells and Extracellular Matrix (ECM) are the two components of what?

The two interacting components of tissues.

What is role of Extracellular Matrix (ECM)

Supports cells, transports nutrients, carries away wastes, and is produced locally by cells.

What is a Cell

The anatomical, functional, and genetic unit of living beings.

Key Characteristics of Cells?

Self-replication, synthesis of macromolecules, environmental interaction, energy production, digestion, catabolic processes aerobic+anaerobic respiration, & mobility.

What are different Shapes of Cells?

Cells can be flat, cuboidal, cylindrical, polyhedral, biconcave, elongated, filiform, or spherical.

What is Size Range of Human Cells?

From as small as lymphocytes (4 µm) to certain neurons (over 1 meter).

What are the Four Basic Types of Tissues?

Epithelial, connective, muscle, and nervous tissue.

Function of Epithelial Tissue?

Lining surfaces or body cavities & glandular secretion.

Function of Connective Tissue?

Support and protection of tissues and organs.

Function of Muscle Tissue?

Strong contraction and body movements.

Function of Nervous Tissue?

Transmission of nerve impulses.

Parenchyma vs Stroma differences?

Parenchyma refers to cells responsible for organ functions; stroma refers to supporting cells.

Why Are Tissues Sectioned?

Most tissues are too thick for light to pass through.

Steps in Preparing Tissue Sections

Sampling, cutting into smaller pieces, preparation, cutting with a microtome, assembling, staining, drying, transliteration & extension.

Fixation in Histology?

Preservation of tissue structure using chemicals, Formaldehyde & Glutaraldehyde.

Tissue Embedding Steps?

Dehydration, clearing, infiltration, and embedding.

Thickness of Sections for Light Microscopy

Typically 3-10 µm thick.

Thickness of Sections for Electron Microscopy

Less than 1 µm thick.

What does sectioning involve?

Involves rapidly freezing tissue, fixing it, and cutting slices using a cryostat, semi thin sections, tissue embedded in epoxy or acrylic resin thinner than 2 µm

Why is Staining Necessary in Histology?

Most cells and extracellular material are colorless.

Most Common Stain in Histology?

Hematoxylin & Eosin (H&E).

Hematoxylin Stains which structures?

Nuclei= purple RNA-rich cytoplasm= dark blue-purple.

What does Eosin Stain?

Other cytoplasmic structures and collagen pink. Eosin is considered a counterstain

Resolving Power of a Light Microscope

Approximately 0.2 µm.

Difference between TEM and SEM

TEM produces 2D images due to electrons passing through tissue; SEM produces 3D images by scanning electrons across specimen surface.

What is Enzyme Histochemistry?

Localizes cellular structures using specific enzymatic activity present in those structures.

Examples of Enzymes in Histochemistry

Phosphatases, dehydrogenases, and peroxidase.

Immunohistochemistry

Technique using antibodies to detect specific antigens in tissue sections.

Indirect Method in Immunohistochemistry

Uses unlabeled primary antibody and labeled secondary antibody to amplify the results

In Situ Hybridization (ISH)

Identifies specific gene sequences or RNA by binding complementary nucleic acid strands.

Fluorescence in Situ Hybridization (FISH)

Uses fluorescent probes to detect & localise specific DNA sequences on chromosomes.

Artifacts in Histology

Structural abnormalities not present in living tissue, often from preparation shrinkage.

Importance of 3D Structure consideration in Histology

3D structures must be considered to understand components missing in 2D sections.

Which chemicals are used for fixation?

Formaldehyde & Glutaraldehyde

Which is the more specific method direct or indirect?

Indirect is more specific & widely used

Is polyclonal or monoclonal more specific?

Polyclonal is not as specific, it is used more broadly, monoclonal is more specific