Postnatal development and differentiation of the secretory elements of the rabbit parotid and submandibular glands.

The development of the secretory elements of the parotid and submandibular glands has been examined in postnatal rabbits. In the submandibular gland, there are 2 principal types of secretory cells, serous and mucous. At birth, these occur in approximately equal proportions, and, by 28 days postnatal, the mucous elements greatly outnumber the serous ones. Initially, development of the parotid gland lags significantly behind that of the submandibular gland. Lobules, which are widely separated at birth, appear compact by 28 days postnatal, at which time also serous acinar cells contain an adult content of secretory granules. In both glands, secretory granules develop within component cells of intercalated ducts by 14 days postnatal. Although the glands appear virtually mature by 28 days postnatal, which corresponds approximately to the onset of weaning, minor structural changes occur over the following 3 postnatal weeks.