Epithelial Tissue and Cellular Structures

Comprehensive vocabulary flashcards covering cellular terminology, tissue types, epithelial classifications, intercellular junctions, and cell surface modifications based on lecture notes.

cyto- / -cyte

Prefix and suffix referring to 'cell'.

Intracellular

Located inside the boundaries of a cell.

Extracellular

Located outside the boundaries of a cell.

Intercellular

Located between two or more cells.

Lumen (Luminal)

The inner space of a cell, or the space contained within a tube, cylinder, or sphere.

Polarity

Spatially different segments or regions of the cell’s borders, categorized as apical, basal, and lateral.

Apical (Apex)

The luminal border or surface of a cell.

Basal (Base)

The part of the cell adjacent to the basement membrane and underlying connective tissue matrix.

Lateral border

The side of a cell where attachment to adjacent cells occurs.

Tissue

A group of cells that work together to perform a specific function.

Epithelium

Tissues that line external body surfaces, internal tubes, and some unicellular to multicellular glands.

Connective Tissue

Tissues that connect, bind, and provide structural support.

Muscle Tissue

Tissue uniquely designed for contractility.

Nervous Tissue

Tissue designed to conduct, receive, transmit, integrate, and transduce information from external and internal sources.

Parenchyma

The functional tissue of an organ.

Stroma

The connective tissue framework supporting the organ parenchyma.

Serosa

A thin layer of simple squamous cells that line the outer surfaces of organs within a body cavity; they secrete a watery lubricating fluid.

Mucosa

Specialized epithelia and associated connective tissue lining the luminal surfaces of body tubes and cavities with an external connection; secretes a viscous fluid.

Simple Epithelium

An epithelium consisting of one layer where all cells are attached to the basement membrane.

Stratified Epithelium

An epithelium consisting of two or more layers; only the row adjacent to the basement membrane is attached to it, and it is named by the shape of the surface cells.

Squamous cells

Flat and thin cells with a bulge for the nucleus; appearing like a fried egg.

Cuboidal cells

Cells shaped like cubes, approximately as tall as they are wide.

Columnar cells

Cylinder-shaped cells that are taller than they are wide.

Mesothelium

A specialized simple squamous epithelium that lines the inner surface of body cavities and the outer surface of internal organs (serosa).

Endothelium

A specialized simple squamous epithelium that lines all blood and lymphatic vessels and the internal surface of the heart.

Pseudostratified columnar epithelium

A simple epithelium that appears stratified because nuclei are at different levels, though all cells attach to the basement membrane; commonly found in the respiratory system.

Transitional epithelium (Urothelium)

A type of pseudostratified epithelium found in the urogenital tract that changes shape as organs stretch and relax, often featuring 'pillow' or 'umbrella' cells.

Keratinized Stratified Squamous Epithelium

Found on external body surfaces, characterized by a stratum corneum where cells have lost their nuclei and filled with keratin to resist abrasion and dehydration.

Non-keratinized Stratified Squamous Epithelium

Found in moist regions like the esophagus or cornea; characterized by a stratum superficiale where cells retain pyknotic nuclei.

Pyknotic

Describes nuclei that are shrunken and heterochromatic.

Occluding junctions (Tight junctions)

Junctions that fuse membranes to seal the space between cells, forming an impermeable diffusion barrier near the apical border.

Zonula Adherens

A type of anchoring junction that tends to be circumferential around the cell, located just below the occluding junction.

Desmosome

Anchoring junctions consisting of adhesion plaques and cadherins connected to internal intermediate filaments, common in the epidermis.

Hemidesmosome

A structure that attaches the basal layer of a cell to the basement membrane using integrins.

Gap junctions (Communicating junctions)

Intercellular channels that permit the direct cell-to-cell transfer of ions and small molecules.

Terminal bar

A dense region at the apical pole of adjacent epithelial cells visible by light microscopy, composed of a desmosome, zonula adherens, and zonula occludens.

Basement Membrane (BM)

A specialized connective tissue region adjacent to the basal surface of epithelial cells composed of lamina lucida, lamina densa, and lamina fibroreticularis.

Basal lamina

A modified basement membrane where the lamina fibroreticularis is absent, produced by muscle cells, adipocytes, and neurolemmocytes.

Microvilli

Non-motile microscopic apical projections that increase surface area; known as the brush border in the kidney or striated border in the intestines.

Glycocalyx

A coating of glycoproteins and complex sugars covering the surface of epithelial cells, forming a protective layer on intestinal microvilli.

Stereocilia

Non-motile, very long microvilli that serve to increase surface area.

Cilia

Motile apical projections with a $9 + 2$ microtubule arrangement that facilitate unidirectional transport.

Kinocilium

A flexible, non-motile long cilium found on sensory hair cells of the inner ear.

Flagella

Long, motile, and few (usually one per cell) structural projections used to propel spermatozoa.

Goblet cells

Cells shaped like a wine glass found within pseudostratified columnar epithelium that secrete mucus.