<P> Stratified epithelia (of columnar, cuboidal or squamous type) can have the following specializations: </P> <Table> <Tr> <Th> Specialization </Th> <Th> Description </Th> </Tr> <Tr> <Td> Keratinized </Td> <Td> In this particular case, the most apical layers (exterior) of cells are dead and lose their nucleus and cytoplasm, instead contain a tough, resistant protein called keratin . This specialization makes the epithelium waterproof, so is found in the mammalian skin . The lining of the esophagus is an example of a non-keratinized or "moist" stratified epithelium . </Td> </Tr> <Tr> <Td> Parakeratinized </Td> <Td> In this case, the most apical layers of cells are filled with keratin, but they still retain their nuclei . These nuclei are pyknotic, meaning that they are highly condensed . Parakeratinized epithelium is sometimes found in the oral mucosa and in the upper regions of the esophagus . </Td> </Tr> <Tr> <Td> Transitional </Td> <Td> Transitional epithelia are found in tissues that stretch and it can appear to be stratified cuboidal when the tissue is not stretched or stratified squamous when the organ is distended and the tissue stretches . It is sometimes called urothelium since it is almost exclusively found in the bladder, ureters and urethra . </Td> </Tr> </Table> <Tr> <Th> Specialization </Th> <Th> Description </Th> </Tr> <Tr> <Td> Keratinized </Td> <Td> In this particular case, the most apical layers (exterior) of cells are dead and lose their nucleus and cytoplasm, instead contain a tough, resistant protein called keratin . This specialization makes the epithelium waterproof, so is found in the mammalian skin . The lining of the esophagus is an example of a non-keratinized or "moist" stratified epithelium . </Td> </Tr>

Epithelial tissue and connective tissue come together to form