A 27-year-old female patient presents to her GP

for the second part of a preventive check-up. The patient's blood tests show a

fairly significant anemia. It soon becomes apparent that this is probably due

to a vitamin B12 deficiency, as the patient is a strict vegan and has not

supplemented her diet with this vitamin. During the physical examination, the

doctor notices one more symptom that would confirm this cause. The patient's

tongue has a distinct red colour and is completely smooth. In healthy

individuals, papillae can be observed macroscopically on the surface of the

tongue, which disappear in this condition, known as Hunter's glossitis. The

most common cause is vitamin B12 deficiency. Several types of papillae are

generally found on the tongue. But which of them has keratinized epithelium?