Tissues and Epithelium Review

Vocabulary flashcards covering human tissue classifications, epithelial structures, junctions, polarization, gland types, endothelium, and skin epidermal layers from Lecture 2.

Epithelial tissue

A tissue type that covers body surfaces, lines body cavities, and forms boundaries separating the body from external environments or internal compartments.

Muscle tissue

A tissue type responsible for enabling physical contraction.

Nervous tissue

A tissue type that facilitates communication and control throughout the body.

Connective tissue

A tissue type that provides connection and structural support.

Simple epithelium

Epithelial tissue consisting of a single layer ($1\text{ layer}$) of cells.

Stratified epithelium

Epithelial tissue consisting of multiple cell layers ($>1\text{ layer}$).

Squamous cells

Scalelike epithelial cells.

Cuboidal cells

Cubelike epithelial cells.

Columnar cells

Column-shaped epithelial cells.

Exocrine Glands

Glands with secretory epithelium surrounding a duct that empties secretions such as mucus, saliva, sweat, earwax, oils, and milk out of the body.

Endocrine Glands

Ductless glands that release hormones directly into the blood and circulatory system.

Polarity

A structural and functional asymmetry within epithelial cells, defining distinct apical, basal, and lateral surfaces.

Basement membrane

An acellular layer secreted partly by epithelial cells and connective tissue cells that supports epithelial tissue.

Avascular

Lacking a direct blood supply or blood vessels, forcing cells to rely on diffusion of nutrients from underlying tissues.

Tight junctions

Junctions using claudins and occludins that seal space between cells to prevent paracellular leakage in the apical region of absorptive epithelia.

Adherens junctions

Junctions using cadherins (E-cadherin) and catenins that provide a mechanical link between actin cytoskeletons of adjacent cells.

Desmosomes

Strong spot-like adhesion junctions using desmoglein and desmocollin (cadherins) to resist mechanical stress, abundant in stratified squamous epithelium.

Hemidesmosomes

Junctions using integrins, BP180, and BP230 that anchor the basal surface of epithelial cells to the basement membrane.

Gap junctions

Junctions composed of connexins that enable direct cell-to-cell communication via exchange of ions and small molecules.

Apical surface

The surface of an epithelial cell that faces the lumen or external space.

Basal surface

The surface of an epithelial cell that adheres to the basement membrane.

Carbonic anhydrase

An enzyme in parietal cells that catalyzes the reaction $CO_2 + H_2O \rightarrow H_2CO_3$, which dissociates into $HCO_3^-$ and $H^+$.

Chloride Shift

The transport mechanism in parietal cells where $HCO_3^-$ is released to the blood in exchange for $Cl^-$ entering from the blood.

Endothelium

Simple squamous epithelium lining the inner surface of blood vessel walls, involved in regulating vascular tone, blood clotting, angiogenesis, and immune trafficking.

Continuous Capillaries

Capillaries with tight junctions between endothelial cells that form selective barriers, found in the brain and lungs.

Fenestrated Capillaries

Capillaries containing small pores within endothelial cells to allow higher permeability, found in the kidneys and intestines.

Sinusoidal Capillaries

Capillaries with large gaps between cells to allow passage of large molecules and cells, found in the liver and spleen.

Stratum corneum

The outermost layer of the epidermis consisting of 20 to 30 layers of dead, shedding keratinocytes.

Stratum lucidum

An extra transitional layer of epidermis found only in thick skin that is packed with eleidin in response to mechanical stress.

Stratum granulosum

The epidermal layer where cells accumulate lamellar and keratohyalin granules, undergo apoptosis, flatten, and die.

Stratum spinosum

The epidermal layer where cells begin producing keratin, release glycolipids, and are tightly linked by desmosomes.

Stratum basale

The deepest epidermal layer made of stem cells undergoing mitotic division.

Eleidin

A clear, lipid-rich form of keratin derived from keratohyalin granules present in the stratum lucidum.

Aneural

Lacking nerves or a nerve supply.