Epithelial Tissue

Epithelial tissue

Includes layer of cells that cover internal or external surfaces and glands

What are the characteristics of epithelia?

Cells are bound closely together, surface is exposed to environment or to internal chamber, attached to underlying connective tissue by the basement membrane, has no blood vessels (avascular), damaged epithelial cells are regenerated

What are the functions of epithelia?

Provides physical protection from exposed and internal surfaces, control permeability, provides sensation, produce specialized secretions/glands

Exocrine

Secretions that are discharged onto the surface of epithelium

Endocrine

Secretions that are released into surround tissue fluid and blood mostly hormones

Basement membrane

Connects epithelial cells to the rest of the body and lies between the epithelium and underlying connective tissues

Simple epithelium

A single layer of cells covering the basement membrane, thin, lines digestive and urinary tracts and surfaces of lungs

Stratified epithelium

Provides protection because it has several layer of cells above the basement membrane, found on the surface of the skin, lining of mouth and anus

Squamous epithelium

Cells are thin and flat

Cuboidal epithelium

Squared cells

Columnar epithelium

Tall and slender cells

Simple squamous epithelium

Found in places where absorption takes place, found in kidney tubules, lining of blood vessels

Simple cuboidal epithelia

Provides limited protection and occurs where secretion or absorption takes place, secrete enzymes in pancreas

Simple columnar epithelium

Provides protection in areas of absorption or secretion, lines the stomach

Pseudostratified columnar epithelium

Lines the nasal cavity and trachea

Transitional epithelium

Stretches, it lines the ureters and urinary bladder where large changes in volume occur

Stratified Squamous Epithelia

Found where mechanical stress are severe, found on the surface of the skin and lining of the mouth, tongue, esophagus and anus

Merocrine secretion

Most common way exocrine glands release substances like sweat, saliva, through exocytosis

Apocrine secretion

Secretion occurs through the loss of cytoplasm containing secretory product