Gastrointestinal Tract
and Glands
Answers
201.The answer is d.(Ross and Pawlina, p 63. Kumar, pp 34, 423.)Mal-
lory bodies are derived from keratin intermediate filaments within hepato-
cytes. Hepatic stellate cells (answer a)secrete the collagen that replaces
normal liver parenchyma in cirrhosis. Kupffer cells (answer b)are the
macrophages of the liver. Vimentin (answer c)is the intermediate filament
protein found in cells of mesenchymal origin; the liver and hepatocytes are
epithelial in origin. Desmin (answer e)is the intermediate filament protein
associated with muscle. ALT/SGPT and AST/SGOT are hepatic aminotrans-
ferases. When found in the blood they are indicative of liver damage.
202.The answer is c.(Johnson, pp 1123–1124. Junqueira, pp 293–294,
296–297. Ross and Pawlina, pp 528–530.)In the resting parietal cell, the pro-
ton pump (H+,K+-ATPase) is found in the tubulovesicle membranes that are
located intracellularly (answer a). The sequestration of the proton pump in
intracellular tubulovesicles in the resting state prohibits secretion. On acti-
vation of the parietal cell through Ca^2 +and diacylglycerol second messen-
gers, the tubulovesicle membranes fuse with the plasma membrane by
exocytosis. Histamine (answer e), along with gastrin and acetylcholine,
activate the parietal cell. Na+,K+-ATPase located in the basal membrane, and
the chloride channel (answer b)of the apical plasma membrane maintain
the appropriate ionic gradients to facilitate acid secretion. Carbonic anhy-
drase, a cytoplasmic enzyme, catalyzes the formation of carbonic acid
(H 2 CO 3 ) from carbon dioxide, which is the source of protons in the parietal
cell and other cell types, such as the osteoclast, that also depend on a pro-
ton pump (answer d).After dissipation of the stimulus (i.e., gastrin, acetyl-
choline, or histamine) or exposure to an H 2 blocker, the parietal cell returns
to the resting state. This involves the recycling (endocytosis) of membrane
to reform the tubulovesicular arrangement within the cytoplasm.
203.The answer is a.(Junqueira, pp 83, 299–303.)Goblet cells secrete
mucus from their apical surface (domain), whereas enteroendocrine cells
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