Epithelium Michael Hall Ph D University of California

Epithelium Michael Hall Ph. D University of California Los Angeles

Features common to all epithelia 1. 2. 3. 4. The cells are closely packed together The cells are polarized The apex always faces an open space The base always sits on a basement membrane

Epithelial cells are closely packed

Epithelial cells always have a free surface and sit on a basement membrane Free Surface Lamina propria

Epithelium Basement membrane Note that both of the epithelia face a free surface Basement membrane Epithelium

Types of Epithelium Simple One cell layer Stratified More than one cell layer

Types of Epithelium 1. Simple squamous 2. Simple cuboidal 3. Simple columnar 4. 5. 6. Stratified squamous Stratified cuboidal Stratified columnar 7. Pseudostratified 8. Transitional

Simple squamous epithelium Free space Basement membrane Connective tissue

Simple squamous epithelium (endothelium) lining an arteriole endothelium

Simple cuboidal epithelium (kidney) Basement membranes Free surface

Simple epithelia in kidney medulla scu ssq scu* ssq scu

Simple columnar epithelium (duodenum)

Stratified Squamous Epithelium (cornea) free surface bm ct

Stratified Squamous Epithelium free surface basement membrane squamous cells

Stratified Cuboidal Epithelium Connective tissue Duct of sweat gland Basement membrane

Stratified Columnar Epithelium (urethra) lp Columnar cells bm

Pseudostratified Epithelium

Pseudostratified Columnar Epithelium (duodenum) Basement Membrane Basal cells

Transitional Epithelium (Urinary system)

Transitional Epithelium (relaxed -top layer of cells is cuboidal) basement membrane Transitional Epithelium basement membrane (stretched-top layer of cells is squamous)

Mesothelium is the name given to the simple squamous epithelium that lines the closed cavities of the body endothelium Endothelium

Basement membranes

Simple squamous epithelium Basement membrane Connective tissue

Basement Membrane of epithelium

Molecular structure of extracellular matrix forming the basement membrane Inside of cell

Junctional Complexes

‘Terminal Bars’ between epithelial cells

Epithelial Junctional Complex Z. occludens Z. adherens Cell 1 Cell 2 Desmosome

Components of the Epithelial Junctional Complex 1 2 1. 2. 3. Z. occludens Z. adherens Macula adherens (desmosome) 4. Gap junction 5. Hemidesmosome 3 5 4

Cell 1 Generalized Structure of a Junctional Complex Cell 2

Connexon 2 Connexon 1 Gap Junction < 1, 500 Da > 1, 500 Da

Surface Specializations of Epithelial Cells

Villin Actin Fimbrin Myosin Spectrin Structure of a microvillus

Stereocilia in the Epididymis Stereocilia

Cilia in the Respiratory Mucosa Cilia

cilia microvilli

Components of a Mucosa Basement membrane Mucosa

The End Whoopee !!