General Histology and Epithelial Tissues

Vocabulary practice flashcards generated from the General Histology lecture transcript and figures covering basic tissue definitions, epithelial tissue classifications, cell junctions, and glandular types.

The Cell

The smallest structure of all tissues.

The Tissue

Formed of a group of similar cells specialized to perform a specific function.

The Organ

Formed of different tissues to perform a specific function.

The System

Formed of a group of organs performing the same function.

Covering & Lining Epithelium

Membranes that cover the surface (e.g., the skin) or line a cavity (e.g., mucous membrane of the intestine).

Glandular Epithelium

Epithelial cells specialized to form a gland for secretion.

Neuro-epithelium

Epithelial cells modified to receive stimuli and act as receptors for different sensations.

Intercellular Cell Junctions

Structures holding epithelial cells together, including occluding junctions, adhering junctions, desmosomes, and gap junctions.

Tight Junctions (Zonula Occludens)

Occluding junctions that act as a selective diffusion barrier, preventing the diffusion of water-soluble molecules.

Adhering Junctions (Zonula Adherens)

Cell-cell junctions formed by cadherin protein.

Desmosomes (Macula Adherens)

Junctions found among cells under continuous stress (e.g., cardiac cells and skin), with intermediate filaments running into the cytoplasm.

Hemidesmosomes

Junctions that lie on the basal membrane to help stick epithelial cells to the underlying basal lamina.

Gap Junctions (Nexus)

Communicating junctions formed by connexin proteins that create continuous channels allowing inorganic ions and small water-soluble molecules to pass, but not proteins, nucleic acids, or sugars.

Simple Epithelium

Epithelium formed of ONE layer of cells.

Stratified Epithelium

Epithelium formed of MANY layers of cells.

Simple Squamous Epithelium

Epithelium formed of one layer of flat polygonal cells with horizontal nuclei; allows passage of fluids and gases, smooth passage of blood and lymph, and free mobility.

Endothelium

Simple squamous epithelium lining lymph and blood vessels as well as heart chambers.

Mesothelium

Simple squamous epithelium lining serous membranes (pleura, pericardium, and peritoneum).

Simple Cuboidal Epithelium

Epithelium formed of one layer of cuboidal cells with central nuclei, functioning in ion exchange (e.g., wall of thyroid follicle & kidney tubules).

Simple Columnar Epithelium

Epithelium formed of one layer of tall cells with oval basal nuclei and scattered mucus-secreting goblet cells (e.g., lining of small intestine).

Simple Columnar Ciliated Epithelium

Epithelium formed of one layer of tall ciliated cells with oval basal nuclei (e.g., lines Fallopian tube and bronchioles).

Pseudostratified Columnar Epithelium

Epithelium formed of one layer of columnar cells with nuclei appearing at two levels, giving the false appearance of two layers (e.g., vas deferens & epididymis).

Pseudostratified Columnar Ciliated Epithelium

Ciliated pseudostratified columnar epithelium with goblet cells, lining upper respiratory passages such as the trachea.

Keratinizing Stratified Squamous Epithelium

Epithelium formed of 5-30 layers of cells (basal low columnar, middle polygonal, superficial flat) with a surface layer of keratin (e.g., skin, external auditory meatus, vestibule of nose, anus).

Non-Keratinizing Stratified Squamous Epithelium

Stratified squamous epithelium without a keratin layer, lining wet surfaces exposed to friction (e.g., cornea, vocal cords, esophagus, vagina, lower part of urethra).

Stratified Cuboidal Epithelium

A rare epithelium formed of two layers of cuboidal cells, found in ducts of sweat glands and parts of male urethra.

Stratified Columnar Epithelium

A rare epithelium with a cuboidal basal layer and columnar superficial layer, found in the largest ducts of salivary glands (parotid & submandibular).

Transitional Epithelium

Epithelium found in urinary organs that changes its shape and layer count based on functional state (6-8 layers when empty, 2-3 layers when distended).

Endocrine Glands

Ductless glands that release hormones directly into blood capillaries.

Exocrine Glands

Glands with well-formed ducts that release chemical secretions onto surfaces.

Mixed Glands

Glands that are partly endocrine and partly exocrine (e.g., the Pancreas).

Merocrine Secretion

Mode of secretion where only the secretory product is released without cell substance loss (e.g., sweat & submandibular glands).

Apocrine Secretion

Mode of secretion where the secretory product and part of the cell cytoplasm are released (e.g., mammary gland).

Holocrine Secretion

Mode of secretion where the cell dies and becomes the secretion (e.g., sebaceous gland).

Goblet Cells

Mucus-secreting cells found scattered within simple columnar and pseudostratified columnar epithelia.