embryology

Development of salivary gland

CLASSIFICATION OF SALIVARY GLANDS

They could be classified as :
• Major salivary glands
• Minor salivary glands
Or according to their secretion type in to:
• Mucous salivary glands
• Serous salivary glands
• Mixed salivary glands

The parotid glands begin to develop at 4 to 6 weeks of embryonic life.

The submandibular glands at 6 weeks
The sublingual and minor salivary glands at 8 to 12 weeks.


The origin of epithelial bud is ectodermal in parotid gland and endodermal in submandibular and sublingual gland.

STAGES OF DEVELOPMENT

STAGE 1


Bud formation: Just as for teeth, the individual salivary glands arise as a proliferation of oral epithelial cells, forming a focal thickening that grows into the underlying ectomesenchyme. Continued growth results in the formation of a small bud.

STAGE 2

Formation and growth of epithelial cord

STAGE 3


Initiation of branching in terminal parts of epithelial cord and continuation of glandular differentiation


STAGE 4

Dichomatous branching of epithelial cord and lobule formation

STAGE 5

Canalization of presumptive ducts.

The lumin form within the ducts before they develop within the terminal buds. Some studies have
suggested that lumen formation may involve apoptosis of centrally located cells in the cell cords.

STAGE 6

Cytodifferentiation:

the epithelium consists of two layers of cells.

1- The cells of the inner layer eventually differentiate into the secretory cells of the mature gland, mucous or serous, depending on
the specific gland.






2- Some cells of the outer layer form the contractile myoepithelial cells that are present around the secretory end pieces.



Thicker partitions of connective tissue (septa), continuous with the capsule and within which run the nerves and blood vessels supplying the gland, invest the excretory ducts and
divide the gland into lobes and lobules