What are the main types of epithelial tissue?

Epithelial tissue is primarily classified based on cell layers and shape. The main types are simple epithelium (a single layer of cells), compound (stratified) epithelium (multiple layers of cells), and transitional epithelium (a special stratified type found in the urinary tract).

Where is transitional epithelium found and what is its function?

Transitional epithelium lines the urinary tract, including the ureter, bladder, and urethra. Its key function is to stretch and flatten as the bladder fills, allowing for expansion without tearing. It consists of three layers: superficial umbrella cells, intermediate pear-shaped cells, and basal cuboidal/columnar cells.

What are the differences between microvilli, stereocilia, and cilia?

These are surface specializations of epithelial cells with distinct structures and functions. Microvilli are short, finger-like projections that increase surface area for absorption, found in the small intestine and gallbladder. Stereocilia are long, non-motile structures that enhance absorption or act as sensory transducers, found in the epididymis and inner ear. Cilia are motile structures that move mucus or ova, found in the respiratory tract and fallopian tubes.

What is the difference between keratinized and non-keratinized stratified squamous epithelium?

Stratified squamous epithelium has two main subtypes based on surface cell characteristics. Keratinized epithelium is found in the skin epidermis, with dead, keratinized surface cells that provide protection. Non-keratinized epithelium is found in moist surfaces like the oral cavity, vagina, and anal canal, with living surface cells that remain moist and flexible.

What are examples of simple epithelium and where are they located?

Simple epithelium includes several types based on cell shape. Simple squamous consists of flat cells found in alveoli, endothelium, and mesothelium. Simple cuboidal has cube-like cells found in thyroid follicles and the germinal epithelium of the ovary. Simple columnar features tall cells lining the GI tract, gallbladder, and bile duct. Pseudostratified ciliated columnar appears stratified but is single-layered, found in the respiratory tract.

How does epithelial tissue regenerate?

Epithelial tissue has a high regenerative capacity, meaning it can quickly repair and replace damaged cells. The regeneration time varies from days to weeks depending on the specific location in the body, such as faster turnover in the skin or slower in other areas.

Epithelial Tissue – Types, Functions & Examples