Q.State various structural modification in a cell involved in secretion?

Answer 1

During the period of rest, i. e., no secretion flowing from the duct, and the gland being pale, the gland cells in the acini undergo a change which may be compared with that observed in the cells of the serous salivary glands. The division of the row of cells lining the acinus, into a central granular and outer clear zone, has already been mentioned.

Immediately after very active secretion, the central granular zone is reduced to a minimum, owing to the paucity of granules; and the outer zone occupies the greater part of the cell, the entire substance of which stains readily and looks like ordinary protoplasm. After rest, however, the granules reappear, and after the lapse of a short quiescent period, the inner granular zone has again encroached on the outer, owing to the accumulation of granules which, rapidly increasing, fill the greater part of the cells, and cause them to bulge inward and occlude the lumen of the gland. As digestion proceeds, the cells undergo a slight change in form, so that each individual cell is more distinctly seen, and its angles are retracted, giving a notched appearance to the margin of the acinus. The blood supply during this period is much increased, red arterial blood flowing from the veinlets of the gland. At the same time the granules are diminished in number, escaping at the free central margin of the cells into the lumen, toward which they appear to crowd, leaving the outer zone once more clear and free from granules, while the lumen of the saccule and of the ducts is filled with secretion.