Types of Epithelium

© 2013 Pearson Education, Inc. Classification of Epithelia All epithelial tissues have two names – One indicates number of cell layers Simple epithelia = single layer of cells Stratified epithelia = two or more layers of cells – Shape can change in different layers – One indicates shape of cells Squamous Cuboidal Columnar In stratified epithelia, epithelia classified by cell shape in apical layer

© 2013 Pearson Education, Inc. Figure 4.2a Classification of epithelia. Basal surface Stratified Classification based on number of cell layers. Basal surface Simple Apical surface

SIMPLE SQUAMOUS EPITHELIUM Single layer of thin, flattened cells Broad thin nucleus (disc shaped) Fxn: allows passage of materials by diffusion and filtration where protection is not important Examples: air sacs (alveoli) Capillary walls, lining the heart, lining of ventral body cavity, kidney glomeruli

Simple Cuboidal Epithelium Single layer of cube shaped cells Centrally located, spherical nucleus FXN: Secretion and absorption Ex: ovaries, kidney tubules, salivary glands, thyroid, pancreas, liver

Simple Columnar Epithelium Elongated (longer than they are wide) Nuclei located near/on basement membrane (often you will find microvilli on surface) (also find goblet cells)

Simple Columnar Found: Lining most of Digestive tract (non-ciliated type), gallbladder, excretory ducts of some glands; small bronchi, uterine tubes, regions of uterus Function: Absorption, secretion of mucous, enzymes and other substances

Simple Columnar

Stratified Squamous Epithelium Multiple layer of squamous cells Two Main Types 1. Keratinized  outer layer of epidermis of the skin. 2. Non-keratinized Ex: mouth, throat, anus (cells on free surface remain alive) Definitely Protection!!

Stratified cuboidal Epithelium 2-3 layers of cuboidal cells (form lining of lumen) -protection -sweat glands, mammary glands, salivary glands, glands of pancreas

Stratified Columnar RARE!!! 2-4 layers of elongated cells Protection Ex: Male urethra, Vas deferens, parts of pharynx

Pseudostratified Columnar Appears to be stratified or layered. (BUT THEY ARE NOT)!! Cell nuclei are actually at different levels in the row, but all cells are attached to the basement membrane. Usually, but not always ciliated. Protection and Secretion Ex: Trachea lining in the respiratory system

Transitional Epithelium Specialized epithelium designed to change in response to increased tension. Stretches, changing apical cuboidal cells into squamous cells. Many Layers Ex: Bladder, ureters, parts of urethra

Transitional