Histological Tissue Types: Epithelial Tissues

Flashcards covering epithelial tissue classification, morphology, staining patterns, polarity, basement membrane properties, and clinical correlations like Bullous Keratopathy based on lecture notes.

What is the etymological origin and meaning of the word "histology"?

"Histology" comes from the Greek words "Histos" (meaning tissue) and "Logos" (meaning study of), defining it as the study of tissues.

What cellular structures are stained blue by Hematoxylin in standard H&E staining?

Hematoxylin stains cell nuclei blue, as well as rough endoplasmic reticulum, ribosomes, collagen, myelin, elastic fibers, and acid mucins.

What cellular components are stained pink by Eosin in standard H&E staining?

Eosin stains cytoplasm and collagen pink.

Why do hydrophobic, lipid-rich structures appear clear on Hematoxylin and Eosin (H&E) stained slides?

Hydrophobic, lipid-rich structures (such as adipocytes, myelin around axons, and Golgi apparatus membranes) tend to remain clear because they do not readily bind the water-based H&E stains.

What are the four basic types of animal tissue?

1. Epithelial tissue
2. Connective tissue
3. Muscle tissue
4. Nervous tissue

What are the two main anatomical types of epithelia?

Surface epithelia (which line all body surfaces and cavities) and solid organs (exocrine and endocrine glands).

What defines structural polarity in epithelial tissue?

Epithelial cells exhibit polarity via an apical domain exposed to the outside or luminal space, a basal domain attached to the basement membrane, and lateral domains attached to neighboring cells.

How do epithelial cells receive oxygen and nutrients given that blood vessels never cross the basement membrane?

Epithelial cells rely entirely on diffusion of nutrients and oxygen from underlying supporting connective tissue across the basement membrane.

What type of intermediate filament is exclusively expressed by all epithelial cells?

Keratins, which form the epithelial cytoskeleton and anchor cell junctions like desmosomes and hemidesmosomes.

How are simple epithelia functionally distinguished from stratified epithelia?

Simple epithelia consist of a single layer of cells specialized for diffusion, absorption, and secretion with no abrasion resistance, whereas stratified epithelia contain two or more layers providing a protective barrier.

What are the primary functions and common body locations of simple squamous epithelium?

Functions: fluid transport, nutrient exchange, and gaseous exchange. Locations: blood and lymph conduits (endothelium), pulmonary alveoli, body cavity membranes (mesothelium), and the renal nephron loop.

What are the morphological features and key locations of simple cuboidal epithelium?

Morphology: single layer of square-shaped (side view) and polygon-shaped (top view) cells with a centrally located nucleus. Locations: kidney tubules/medulla/collecting ducts, mammary glands, and sweat gland ducts.

What are the main functions and distribution of simple columnar epithelium?

Functions: absorption and secretion. Locations: small intestine, large intestine, gall bladder, and stomach.

Where is ciliated simple columnar epithelium found in the human body?

In the female reproductive tract and the bronchi/bronchioles of the respiratory system.

What is the key location difference between stratified squamous non-keratinized (SSNK) and keratinized (SSK) epithelium?

SSNK lines moist protective surfaces like the mouth, esophagus, cornea, and vagina, while SSK forms the impermeable outer layer of the skin (epidermis).

Why is pseudostratified columnar epithelium classified as "pseudo" stratified?

All cells are attached to the basal lamina, but not all cells reach the apical surface, and their nuclei sit at varying heights, giving the illusion of multiple cell layers.

How does the morphology of transitional epithelium change between empty and distended states?

When non-distended (empty bladder), superficial cells are large, cuboidal, and dome-shaped (sometimes binucleated); when distended (full bladder), the layer stretches and flattens into a squamous-like appearance.

What structure shown in the image below consists of hexagonal cells that actively maintain corneal dehydration?

Corneal endothelium

What pathological condition of the cornea is depicted in this image, marked by arrows indicating fluid-filled subepithelial bullae?

Bullous Keratopathy (BK)

What is the primary etiology and curative treatment for Bullous Keratopathy (BK)?

The most common cause is Fuchs corneal endothelial dystrophy (or endothelial trauma), and corneal transplantation is usually curative.