epithelial tissue layers

HeLa cells

human squamous cell carcinoma cells that have not stopped replicating since they were collected 1951

HeLa cells have led to

medical discoveries in cancer, immunology and infectious disease research

• better understanding of how squamous cell epithelial tissues function

HeLa cells were collected from

Henrietta Lacks in 1951 at johns hopkins university hospital

review: epithelial tissue

• covers body surfaces

• controls nutrient flow to underlying tissues

• houses secretory cells

• responsive to external stimuli and aids in sensory communication

epithelial tissues derived from

all 3 germ layers

1. ectoderm → epidermis

2. mesoderm → lining of blood vessels

3. endoderm → lining of GI tract

relative composition of epithelial membranes can vary based on…

1. layers of epithelial cells

2. amount of connective tissue

epithelial tissue types based on…

cell shape/structure and layer/thickness

squamous cell shape

thin, pancake-shaped

cuboidal cell shape

all cell dimensions relatively equal

columnar cell shape

slender and elongated

simple layer

single layer

• all cells attached directly to basal lamina; nuclei in straight line

simple layer function

allows maximal secretion and/or absorption

stratified layer

many layers of cells that shed easily

stratified layer function

protects underlying tissue from abrasion

• transitional: specialized stratified layers of cuboidal epithelial cells

pseudostratified layer

single layer of columnar cells

simple squamous epithelial function

allow material to pass through by diffusion and filtration, and secretes lubricating substance

simple cuboidal epithelial function

secretes and absorbs

simple columnar epithelium function

absorbs; it also secretes mucous and enzymes

pseudostratified colum nar epithelium

secretes mucus; ciliated tissue moves mucus

stratified squamous epithelium function

protects against abrasion

stratified cuboidal epithelium function

protective tissue

stratified columnar epithelium function

secretes and protects

transitional epithelium function

allows the urinary organs to expand and stretch