A 22-year-old patient

presents for a colonoscopy to confirm a diagnosis of Crohn's disease or

ulcerative colitis. He has been suffering from crampy abdominal pain with

watery diarrhea with admixture of blood and mucus for several weeks. During the

endoscopy, a typical picture of mucosal damage by these autoimmune

inflammations is described and a biopsy is taken for histological examination,

which finally establishes the diagnosis of ulcerative colitis. Ulcerative

colitis is a rare autoimmune type of

A 9-year-old boy is brought to the physician by his mother

because of a few-day history of fever and cough. He has

had similar episodes of inflammation of the respiratory tract with fever, cough, and runny nose with the presence of thick, colored mucus

A 12-year-old female patient presents for an

orthodontic check-up after braces placement. In one spot, part of her braces

are slightly pushing and interfering. There is a white spot that cannot be

wiped off. As a result of mechanical irritation, the mucous membrane of the

vestibular surface of the lip has become irritated and keratinised. Such spots

are known as leukoplakia and, in addition to mechanical irritation, a number of

other factors may be involved in their formation. However, the exact cause has

not yet been described. The transformation of which epithelium is involved

here, which normally forms the oral mucosa?