HISTOLOGY

EPITHELIUM CELLS

Stem Cells

• Early cells that are not programmed yet

• As development of the organism occurs, these stem cells become specialized.

• RISK: If function of the body rely on specialized cells, if those cells are destroyed or disabled, it could lead to disaster for the organism

Primary Tissue

• Tissue: Cells with the same function and structure.

• There are four primary tissues:– Epithelium– Connective– Nervous– Muscle

EPITHELIAL TISSUE

• Specialized Characteristics– Fit closely together to form sheets

• Lots of tight junctions

– One surface exposed to body’s exterior or cavity– Basement Membrane

• Foundation for new cells

– Avascular• No blood supply of their own• Depend on Diffusion (Capillaries)

– Regenerate Easily

Epithelium Classification

Simple Squamous Epithelium• “Floor Tiles” Filtration, Diffusion

• Serous membranes, O2 and CO2 Diffusion, Capillaries

Simple Squamous Epithelium

Simple Cuboidal Epithelium• Glands, Ducts, Salivary Glands • One layer of cuboidal cells resting on a basement membrane

SIMPLE CUBOIDAL Epithelium

Simple Cuboidal Epithelium

Simple Columnar EpitheliumGoblet cells produce a lubricating mucus. Digestive Tract, Mucous membranes.

Simple Ciliated Columnar Epithelium

Pseudostratified Ciliated Epithethium

• Respiratory Tract; nuclei appear at different heights

Stratified Squamous Epithelium• Abuse/Friction, esophagus, mouth, outer skin

Stratified Squamous Epithelium

Stratified Squamous Epithelium

Stratified Cuboidal Epithelium• Usually found with 2 layers being cuboidal• Ducts of glands

Stratified Cuboidal Epithelium

Stratified Cuboidal Epithelium

Stratified Columnar EpitheliumDucts of large glands, basal cells vary in size. RARE

Transitional Epithelium• Highly modified, urinary bladder, ureters,

Transitional Epithelium