Which of the following growth alteration is an example of hyperplasia rather than metaplasia?
Hyperplasia is an increase in cell number, whereas metaplasia is the replacement of one adult cell type by another adult cell type. Hyperplasia occurs when there is increased trophic stimulation (e.g., hormones, growth factors), increased functional demand, or persistent cell injury. Only labile and stable cells undergo hyperplasia; labile cells have stern cells that frequently divide, and stable cells have resting cells that are stimulated to enter the cell cycle. The presence of increased goblet cells in the mainstem bronchus of a smoker is an example of hyperplasia, because goblet cells are normally present in this area. However, their presence in the terminal bronchiole or gastric mucosa, where they are not normally found, is an example of metaplasia. Squamous epithelium in the bladder of a patient with Schistosoma haernatobium is an example of metaplasia, because the epithelium of a normal bladder is transitional. Irritation from the eggs of the schistosomes induces squamous metaplasia and the potential for dysplasia and squamous carcinoma. A distal esophagus with glandular epithelium intermixed with squamous epithelium is an example of Barrett esophagus. Chronic acid injury to the distal esophagus from gastroesophageal reflux stimulates the formation of mucoussecreting glandular epithelium, which is a type of glandular metaplasia and predisposes the patient to adenocarcinoma. Goblet and Paneth cells in the glands of the gastric mucosa is called intestinal metaplasia and is commonly seen in chronic atrophic gastritis of the body and fundus (type A) or pylorus and antrum (type B). It is a precursor lesion of adenocarcinoma of the stomach. Squamous epithelium in the mains tern bronchus of a smoker is squamous metaplasia, because normal epithelium is pseudostratifiecl, ciliated, and columnar. The squamous epithelium is a reaction to injury induced by cigarette smoke. It predisposes the patient to squamous dysplasia and carcinoma.
Increased gobbler cells in the mainstem bronchus of a smoker
Squamous epithelium in the bladder of a patient with Schistosoma haematobium
Distal esophagus with glandular epithelium intermixed with squamous epithelium
Goblet and Paneth cells in the glands of the gastric mucosa