Introduction to Cell Histology – Key Vocabulary

A comprehensive set of vocabulary flashcards covering major terms, structures, stains, tissue types, processing steps, and pathological concepts introduced in the lecture on cell histology.

Histology

The study of cells and tissues and their microscopic structure.

Tissue

A group of similar cells performing a common function.

H&E Stain

Routine stain using hematoxylin (blue-purple) and eosin (pink-red) to impart contrast to tissues.

Hematoxylin

Basic, positively charged blue dye that binds nucleic acids and other negatively charged (basophilic) structures.

Eosin

Acidic, negatively charged pink-red dye that binds positively charged (acidophilic) structures such as cytoplasm and collagen.

Basophilic

Describes cellular structures that stain with basic dyes like hematoxylin (e.g., DNA, rRNA).

Acidophilic (Eosinophilic)

Describes structures that stain with acidic dyes like eosin (e.g., cytoplasm, extracellular matrix).

Basophil (leukocyte)

White blood cell with cytoplasmic granules that bind hematoxylin intensely.

Acidophil (eosinophil)

White blood cell whose granules bind eosin strongly.

Fixation

Initial tissue-processing step that inactivates degradative enzymes and preserves morphology.

Dehydration

Removal of water from tissue using graded alcohols during processing.

Clearing

Replacement of alcohol with an organic solvent to prepare tissue for infiltration.

Infiltration

Penetration of tissue by melted paraffin or plastic to enable sectioning.

Embedding

Allowing infiltrated tissue to harden in paraffin/plastic to create a block for cutting.

Microtome

Instrument that slices hardened tissue blocks into thin (1–10 µm) sections.

Sectioning Artifact

Artificial defect (fold, tear, chatter) introduced during cutting of tissue sections.

Basement Membrane

Specialized extracellular layer underlying epithelium; composed of basal and reticular laminae.

Apical Surface

The free (luminal) surface of an epithelial cell.

Basal Surface

Portion of an epithelial cell contacting the basement membrane (abluminal side).

Lumen

Central cavity or channel within a tubular organ or duct.

Adluminal

Toward the lumen or free surface (apical).

Abluminal

Away from the lumen; toward the basal side or basement membrane.

Mesothelium

Simple squamous epithelium lining closed body cavities (pleura, peritoneum, pericardium).

Endothelium

Simple squamous epithelium lining blood and lymphatic vessel lumens.

Epithelium

Tissue category that covers surfaces, lines cavities, and forms glands; cells are tightly packed and avascular.

Simple Epithelium

Single layer of epithelial cells (e.g., simple squamous, cuboidal, columnar).

Stratified Epithelium

Multiple layers of epithelial cells; named by shape of cells at the apical surface.

Glandular Epithelium

Epithelial tissue specialized for secretion; forms exocrine or endocrine glands.

Exocrine Gland

Secretes products via ducts to an epithelial surface.

Endocrine Gland

Ductless gland that releases hormones into the bloodstream; typically highly vascular.

Connective Tissue

Tissue type providing support and connection; composed of cells, fibers, and ground substance.

Ground Substance

Amorphous material of extracellular matrix occupying spaces between cells and fibers.

Collagen Fiber

Strong, acidophilic extracellular fiber composed of collagen protein; stains pink in H&E.

Elastic Fiber

Stretchable extracellular fiber composed of elastin; visualized with Weigert’s elastic stain.

Loose Connective Tissue

Connective tissue with abundant ground substance and loosely arranged fibers.

Dense Regular Connective Tissue

Connective tissue with parallel bundles of collagen fibers and fibroblasts; resists tensile stress (e.g., tendon).

Dense Irregular Connective Tissue

Connective tissue with randomly arranged collagen fibers; provides multidirectional strength (e.g., dermis).

Cartilage

Firm connective tissue with chondrocytes and avascular ECM rich in proteoglycans.

Bone

Mineralized connective tissue containing osteocytes within a rigid ECM.

Adipose Tissue

Connective tissue specialized for lipid storage; cells appear as empty vacuoles in H&E.

Blood

Fluid connective tissue consisting of cells suspended in plasma.

Mucosa

Mucous membrane composed of epithelium, basement membrane, and underlying lamina propria.

Submucosa

Fibrous supporting connective tissue layer deep to mucosa.

Muscularis Mucosae / Tunica Muscularis

Smooth muscle layer beneath submucosa causing local movements of mucosa.

Serosa

Outer covering of organs within body cavities; simple squamous epithelium plus connective tissue.

Capsule (organ)

Connective tissue layer enclosing an organ.

Cortex (organ)

Outer region of an organ.

Medulla (organ)

Inner region of an organ.

Parenchyma

Functional cellular component of an organ.

Stroma

Supporting connective tissue framework of an organ.

Muscle Tissue

Contractile tissue type; includes skeletal, cardiac, and smooth muscle.

Skeletal Muscle

Striated, multinucleated voluntary muscle with peripheral nuclei.

Cardiac Muscle

Striated, branched involuntary muscle with central nucleus and intercalated discs.

Smooth Muscle

Non-striated, spindle-shaped involuntary muscle with single central nucleus.

Cytoskeleton

Network of microtubules, actin filaments, and intermediate filaments providing structural support to cells.

Rough Endoplasmic Reticulum (rER)

Membranous organelle studded with ribosomes; basophilic due to rRNA; site of protein synthesis.

Smooth Endoplasmic Reticulum (sER)

Membranous organelle lacking ribosomes; functions in lipid synthesis and detoxification; usually unstained in H&E.

Secretory Vesicle

Membrane-bound packet of secretory product; may appear as acidophilic or basophilic granules.

Inclusion

Non-membranous cytoplasmic storage product (e.g., glycogen, lipid droplets, pigment).

Neuron

Excitable cell that transmits electrical impulses; contains prominent cell body, axon, and dendrites.

Glial Cell

Supportive cell in nervous tissue; surrounds neurons and maintains microenvironment.

Axon

Long neuronal process that conducts impulses away from the cell body.

Immunohistochemistry (IHC)

Technique using antibodies tagged with labels to detect specific proteins in tissue sections.

In Situ Hybridization (ISH)

Method using labeled nucleic acid probes to detect specific DNA or RNA sequences in tissue.

FISH (Fluorescence In Situ Hybridization)

Fluorescent ISH technique commonly used to visualize genes or chromosomal abnormalities.

Trichrome Stain

Three-color stain (e.g., Mallory) highlighting collagen in blue or green and muscle in red.

PAS Stain

Periodic acid–Schiff reaction that stains polysaccharides, glycogen, and basement membranes magenta.

Weigert’s Elastic Stain

Stain that colors elastic fibers dark blue/black, useful for vasculature.

Silver Stain

Impregnation method highlighting basement membranes, reticular fibers, or certain pathogens in black.

Golgi Technique

Silver nitrate method staining entire neurons (cell bodies & dendrites) black for neurological study.

Electron Microscopy

High-resolution imaging technique using electron beams to visualize ultrastructure below light-microscope limits.

Artifact (histology)

Structural distortion or defect introduced during tissue processing (e.g., folds, tears, bubbles).

Metaplasia

Reversible replacement of one mature cell type by another, often in response to stress.

Neoplasia

Pathological proliferation of abnormal cells forming a mass; can be benign, in situ, or malignant.

Hypertrophy

Increase in cell size without increase in cell number.

Hyperplasia

Increase in the number of cells within a tissue or organ.

Ground Rules for Identifying Tissues

Assess cell density, presence of surface, extracellular matrix, nucleus location, and contextual clues to distinguish tissue types.