General Concepts of Epithelium and Histology

Comprehensive vocabulary flashcards covering general histology concepts, epithelial classifications, intercellular junctions, and apical surface modifications based on the lecture transcript.

Intracellular

Located or occurring within a cell.

Extracellular

Located or occurring outside a cell.

Intercellular

Located or occurring between cells.

Four Main Tissues

1) Epithelium, 2) Connective Tissue, 3) Muscle, 4) Nervous Tissue.

Epithelium Functions

Protection (skin), Absorption (lungs, kidney), Excretion (one-way transport), Secretion (serous/mucous), Surface reception (special senses), and Reproductive (gamete production).

Basement Membrane (Epithelium)

An avascular layer on which epithelium rests; it provides nutrients to the cells and changes in it can lead to disease.

Simple Epithelium

A single layer of cells.

Stratified Epithelium

Two or more layers of cells; named by the most superficial layer (apical surface).

Squamous

A cell shape characterized as "Fried egg."

Cuboidal

A cell shape where cells are as tall as they are wide.

Columnar

A cell shape where cells are taller than they are wide.

Mesothelium

Simple squamous epithelium lining the outside of organs.

Endothelium

Simple squamous epithelium lining arteries, veins, and lymphatics.

Pseudostratified Columnar Epithelium

A crowded-looking simple epithelium where all cells contact the basement membrane, but not all reach the free surface.

Transitional Epithelium

A type of pseudostratified epithelium with a scalloped/cobblestone appearance found in the urogenital tract (e.g., bladder); uniquely accommodates stretching.

Stratified Squamous Epithelium

Multiple layers of cells specialized to resist forces of friction; can be keratinized or nonkeratinized.

Anchoring Junctions

Intercellular junctions including Desmosomes and Hemi-desmosomes.

Occluding Junctions

Intercellular junctions known as Tight junctions.

Communicating Junctions

Intercellular junctions including Gap junctions and Chemical synapses.

Basement Membrane Laminae

The several layers of the basement membrane: Lamina lucida, Lamina densa, and Fibroreticular lamina.

Microvilli

Tiny surface projections at the apical pole measuring about $0.1\,\mu m$ in diameter and $1.0\,\mu m$ in length; function to increase surface area for absorption.

Stereocilia

Apical surface modifications that are much longer than microvilli and cilia.

Cilia

Highly motile apical modifications measuring $0.2\,\mu m$ in diameter and $6\,\mu m$ in length; found in airway and female reproductive tracts.

Axoneme

A cylindrical array of microtubules in cilia consisting of $9$ "doublets" and two single centrally located microtubules.

Dynein arms

The force-generating protein found within the structural array of cilia.

Ciliadyskensia

A structural problem in cilia where lungs cannot clear; noted as occurring in Golden Retrievers.