Question

1. Distinguish between chief and parietal cells of the gastric glands

Answer 1

PARIETAL CELLS-

These are the epithelial cells that secrete hydrochloric acid and intrinsic factor.

Found in the lining of fundus and stomach.

FUNCTIONS-

Intrinsic factor- is needed for the absorption of vitamin B12 which is used for the formation of red blood cells.

Hydrochloric acid- it kills microbes in food, it denatures proteins, converts pepsinogen to pepsin.

HISTOLOGY- They have a canaliculus appearance. A canaliculus is an adaptation found on gastric parietal cells. It is a deep infolding, or little channel, which serves to increase the surface area, for secretion of hydrochloric acid and intrinsic factor. The parietal cell membrane is dynamic; the numbers of canaliculi rise and fall according to secretory need. This is accomplished by the fusion of canalicular precursors, with the membrane to increase surface area, and the reciprocal endocytosis of the canaliculi to decrease it.

APPEARANCE- have canaliculus appearance. These are smaller sized cells compared to chief cells.

CHIEF CELLS-

These are the cells which release pepsinogen and chymosin. These synthesise and secrete hydro lytic enzymes which are activated by acidic pH.

Located in the clusters at the base of the gastric glands.

FUNCTIONS-

Pepsin breaks down proteins into peptides.

Gastric lipase splits the triglycerides into fatty acids and monoglycerides.

HISTOLOGY- Gastric chief cells are epithelial cells which are found within the gastric unit or gastric gland, and form the base of the gastric unit. The gastric chief cell has an extensive network of lamellar rough endoplasmic reticulum organized around the nucleus. The gastric chief cell also contains many large secretory vesicles filled with digestive enzymes in the apical cytoplasm.

APPEARANCE- These have serous-secretory appearance.