Epithelial Tissues - Histology Flashcards

Flashcards covering epithelial tissue classification, histology basics, cell polarity, cellular junctions, basement membrane structure, and epithelial clinical conditions such as Bullous Keratopathy.

Histos

A Greek root word meaning tissue.

Logos

A Greek root word meaning study of.

Histology

The study of tissues.

Hematoxylin and Eosin Stain

The most common stain used in histology and pathology, commonly abbreviated as H&E stain.

Hematoxylin

A histologic stain that colors cell nuclei blue, as well as rough endoplasmic reticulum, ribosomes, collagen, myelin, elastic fibers, and acid mucins.

Eosin

A histologic stain that colors the cell cytoplasm pink, as well as collagen.

Hydrophobic Structures in H&E Staining

Structures rich in lipids (e.g., adipocytes, myelin around neuron axons, and Golgi apparatus membranes) that tend to remain clear during H&E staining.

Four Basic Animal Tissue Types

The four fundamental tissue types found in animals: epithelial tissue, connective tissue, muscle tissue, and nervous tissue.

Surface Epithelia

Sheets of epithelial cells that line all body surfaces and cavities.

Solid Organs (Epithelial context)

Epithelial-derived gland structures categorized as exocrine and endocrine glands.

Epithelial Tissue Functions

Major functions including barrier/protection, absorption/diffusion of nutrients/fluids, transport across cellular layers, and synthesis/secretion of hormones, enzymes, and mucous.

Cell Polarity

The structural property of epithelial cells having distinct apical, basal, and lateral domains.

Apical Surface

The free domain of an epithelial cell exposed to the outside environment or luminal space.

Basal Surface

The domain of an epithelial cell attached to the underlying basement membrane.

Lateral Surfaces

The domains of an epithelial cell attached to adjacent neighboring epithelial cells.

Basement Membrane

A thin sheet-like, bi-layered extracellular matrix specialized in attaching and anchoring epithelial and endothelial cells to underlying connective tissue.

Lamina Lucida

The clear, upper electron-lucid layer of the basal lamina within the basement membrane.

Lamina Densa

The electron-dense layer of the basal lamina situated between the lamina lucida and reticular connective tissue.

Reticular Lamina

The connective tissue layer underlying the basal lamina that completes the basement membrane structure.

Avascularity of Epithelium

The characteristic that blood vessels never cross the basement membrane, leaving epithelial cells reliant on diffusion from underlying supporting tissues.

Keratins

Intermediate filament proteins exclusively expressed by all epithelial cells that form the cytoskeleton and anchor desmosomes and hemidesmosomes.

Tight Junction

A cell-cell junction located near the apical domain that seals neighboring cells together, preventing paracellular diffusion.

Adhesive Belt

Also known as adherens junction, a cell-cell junction located below tight junctions that anchors actin filaments between adjacent cells.

Desmosome

A cell-cell junction anchored by keratin intermediate filaments that provides strong mechanical cell-to-cell adhesion.

Hemidesmosome

A specialized cell-matrix junction that anchors the intracellular keratin intermediate filaments of an epithelial cell to the underlying basement membrane.

Gap Junction

An intercellular junction that provides passageways allowing direct chemical and electrical communication between adjacent cells.

Focal Adhesion

A cell-matrix junction connecting the actin cytoskeleton of a cell to the extracellular matrix or basement membrane.

Simple Epithelium

An epithelium composed of a single layer of cells involved in diffusion, absorption, and secretion, offering no protection against abrasion.

Stratified Epithelium

An epithelium composed of two or more layers of cells, primarily serving a protective function.

Squamous Cells

Thin, flattened epithelial cells that resemble fish scales when viewed from the side.

Cuboidal Cells

Epithelial cells that appear square in side view and polygonal from a top view, containing a centrally located nucleus.

Columnar Cells

Tall, rectangular epithelial cells in side view with polygonal top views, containing nuclei typically located near the base.

Microvilli

Microscopic apical cell membrane extensions that function to increase surface area for absorption.

Cilia

Hair-like apical structures capable of coordinated beating to transport mucus or fluids across epithelial surfaces.

Simple Squamous Epithelium

A single layer of tightly packed, flat cells with interdigitations, specialized for fluid transport, nutrient exchange, and gaseous exchange.

Endothelium

Simple squamous epithelial-like tissue lining the internal surfaces of blood vessels, lymphatic vessels, and heart chambers.

Mesothelium

Simple squamous epithelium lining major closed body cavities, including the pleural, pericardial, and abdominal cavities.

Interdigitations

Interlocking membrane boundaries between adjacent simple squamous epithelial cells that enhance structural integrity.

Simple Cuboidal Epithelium

A single layer of cube-shaped cells with central nuclei, functioning primarily in secretion and absorption in kidney tubules, mammary glands, and sweat gland ducts.

Simple Columnar Epithelium

A single layer of tall rectangular cells with basally aligned nuclei, lining the small intestine, large intestine, gall bladder, and stomach.

Metabolic State and Columnar Height

The property where simple columnar epithelial cell height varies from low to high depending on the metabolic rate of the tissue.

Simple Columnar Epithelium with Cilia

A simple columnar epithelium featuring apical cilia, functioning in conduction, transport, and absorption in the female reproductive tract, bronchi, and bronchioles.

Stratified Squamous Epithelium

A multi-layered epithelium with flattened superficial cells designed for protection and resistance to friction and mechanical forces.

Non-Keratinized Stratified Squamous Epithelium (SSNK)

A stratified squamous epithelium where superficial cells retain their nuclei; found in the mouth, esophagus, cornea, and vagina.

Keratinized Stratified Squamous Epithelium (SSK)

A stratified squamous epithelium where superficial cells lose their nuclei and fill with keratin, forming an impermeable layer in the epidermis of the skin.

Stratified Cuboidal Epithelium

A multi-layered epithelium composed of cuboidal cells that functions in transport, absorption, and secretion within salivary and sweat gland ducts.

Pseudostratified Columnar Epithelium

A single layer of columnar cells where all cells rest on the basal lamina but not all reach the apical surface, creating non-aligned nuclei.

Respiratory Epithelium

Ciliated pseudostratified columnar epithelium with mucus-secreting goblet cells that lines the respiratory tract.

Transitional Epithelium (Urothelium)

A specialized stratified epithelium lining the urinary tract that changes shape from cuboidal when non-distended to flattened when distended.

Superficial Cells of Urothelium

Large, rounded, dome-shaped superficial cells in non-distended transitional epithelium that may contain two nuclei and provide a waterproof barrier.

Stratified Columnar Epithelium

A rare epithelium with columnar surface cells lining the conjunctiva of the eye and some large excretory ducts.

Corneal Endothelium Shape

A single layer of simple squamous epithelial-like cells that appear hexagonal when viewed from above.

Corneal Endothelium Function

Active transport of fluid and nutrients into the avascular cornea while pumping excess fluid out to maintain corneal transparency.

Bullous Keratopathy (BK)

A condition causing corneal clouding due to stromal edema resulting from corneal endothelial failure to maintain corneal dehydration.

Epithelial Bullae

Subepithelial fluid-filled blisters that form on the corneal surface in Bullous Keratopathy.

Symptoms of Bullous Keratopathy

Decreased visual acuity, loss of contrast, glare, photophobia, pain, and foreign body sensation upon bullae rupture.

Fuchs Corneal Endothelial Dystrophy

The most common underlying cause of Bullous Keratopathy.

Endothelial Trauma

A secondary cause of corneal endothelial cell loss leading to Bullous Keratopathy.

Complication of Ruptured Bullae

Bacterial invasion of a ruptured bulla leading to corneal ulcer formation.

Treatments for Bullous Keratopathy

Topical dehydrating agents, IOP-lowering agents, therapeutic soft contact lenses, and curative corneal transplantation.

Cornea Barrier Function

Epithelial protection of internal ocular tissues against external pathogens and damage while maintaining optical clarity.

Aqueous Humor

Fluid filling the anterior chamber of the eye from which the corneal endothelium transports nutrients into the avascular corneal stroma.

Limbus

The anatomical border or transition zone between the cornea and the sclera.

Fornix

The junctional fold connecting the palpebral conjunctiva lining the eyelid to the bulbar conjunctiva lining the eyeball.

Ciliary Body

An ocular structure located behind the iris responsible for producing aqueous humor.

Rapid Renewal

The characteristic high rate of cell turnover and regeneration observed in epithelial tissues.

Nephron Loop

A segment of the kidney tubule lined by simple squamous epithelium specialized for fluid exchange.

Kidney Collecting Ducts

Renal tubules in the kidney medulla lined by simple cuboidal epithelium involved in urine transport.

Epidermis

The outermost layer of skin, composed of keratinized stratified squamous epithelium.

Pulmonary Alveoli

Microscopic air sacs in the lungs lined by simple squamous epithelium to facilitate gaseous exchange.

Mucous-Secreting Cells

Specialized cells (such as goblet cells) interdispersed in pseudostratified and simple columnar epithelia that synthesize and secrete protective mucus.

Simple Squamous Epithelium Diagram

Diagram representing simple squamous epithelium, characterized by a single layer of flattened cells resting on a basal lamina.

Simple Cuboidal Epithelium Diagram

Diagram representing simple cuboidal epithelium, characterized by a single layer of square-shaped cells with central spherical nuclei.

Simple Columnar Epithelium Diagram

Diagram representing simple columnar epithelium, characterized by a single layer of tall rectangular cells with basally located oval nuclei.

Pseudostratified Columnar Epithelium Diagram

Diagram representing pseudostratified columnar epithelium, where all cells contact the basement membrane but nuclei appear at varied levels.

Keratinized Stratified Squamous Epithelium Diagram

Diagram showing stratified squamous epithelium with an overlying superficial layer of dead, anucleate keratinized cells.

Non-Keratinized Stratified Squamous Epithelium Diagram

Diagram showing stratified squamous epithelium where superficial flattened cells retain visible nuclei.

Stratified Columnar Epithelium Diagram

Diagram showing stratified columnar epithelium, featuring columnar-shaped cells making up the superficial layer.

Stratified Cuboidal Epithelium Diagram

Diagram showing stratified cuboidal epithelium, consisting of multiple layers of cube-shaped cells.

Transitional Epithelium Non-Distended Diagram

Diagram showing transitional epithelium in an un-stretched, non-distended state, featuring rounded dome-shaped umbrella cells at the surface.