Figure 4.

Development of human salivary glands

All panels are LSFM images of solvent-cleared embryos (A–F) and fetuses (D, E, and G–I) immunostained with anti-Sox9 (A–I) combined with synaptophysin (F, H, and I). Glands immunolabeled with Sox9 were segmented using VR and pseudocolored.

(A–C) Dorsal view of the mouth and tongue of PCW7 (A) and PCW7.5 (B) embryos where the nascent parotid (magenta), submandibular (cyan), and sublingual (yellow) glands were segmented and pseudocolored. (C) shows a lateral view of the parotid (arrow) overlaid on the 3D rendering image (gray) of the face.

(D and E) Branching morphogenesis of the parotid gland and submandibular glands. A unique duct connects the glands to the mouth.

(F–H) Development of the sublingual glands. The first buds are visible at PCW7 and stay rather short until PCW9 when some sublingual glands start ramifying at their apex (F). (G and H) At PCW11.3, the number of glands has increased on both sides and they are distributed beneath the tongue, along all its length, all individually connected to the mouth floor.

(H and I) Both the submandibular (arrowheads in H) and sublingual (arrowheads in I) are densely innervated by synaptophysin+ axons emanating from the chorda tympani branch of the facial nerve (VII).

Scale bars: all panels are counted from left to right for each row; 700 μm in (A), (B), (D, right), and (I); 1 mm in (C), (G), and (H); 200 µm in (D, left and middlepanels); 100 μm in (E, first panel); 300 μm in (E, second and third panels) and (F, third panel); and 500 μm in (E, fourth panel) and (F, all panels except for the third).