Morphogenesis of the dental stalk area in mouse.

<p>Transversal sections through the dental stalk area of the first molar in the lower jaw of mouse. <b>A-D:</b> The dental stalk epithelium (ds) is compact at early developmental stages (E18, P2). <b>E-H:</b> Later in development, small bays of mesenchyme (red arrow) with capillaries disrupt epithelial tissues (P8, P10). <b>I-L:</b> Just before molar eruption, epithelial tissues integrity is disrupted by connective tissue islands (P12 and P14). Degradation of epithelium is obvious during time of eruption (P14 and P16). <b>M,N:</b> At P16, the buccal area of the dental stalk becomes the part of gingiva (g) and area above erupting teeth degrades and deceased tissue is peeled off the epithelium (e). ds—dental stalk, sdl—successional dental lamina. Red arrow—bays of connective tissue protruding into the epithelium. HE—Hematoxylin-Eosin. Epithelial cells are labeled by cytokeratin antibody (brown). Negative cells are counterstained by Hematoxylin (blue nuclei). Scale bar—100 μm. <b>O,O´:</b> Ultrastructure of the dental stalk at stage E18. 1—loops of the basal lamina, 2—basement membrane, 3—mesenchymal cell, 4—glycogen, 5—mitochondria, 6—microvilli, 7—collagen fibrils, 8—cytoplasmatic process of mesenchymal cell. <b>P,P´,P´´,P´´´:</b> Ultrastructure of the dental stalk at stage P2. 1—intercellular spaces between epithelial cells, 2—microvilli of epithelial cells, 3—collagen fibrils, 4—loops of basement membrane, 5—mitochondria, 6—epithelial cells, 7—cytoplasmatic processes of fibroblast, 8—bundles of intermediate filaments. <b>Q,Q´,Q´´,Q´´´:</b> Ultrastructure of the dental stalk at stage P8. 1 - “folding” of lamina densa, 2—loops of basement membrane, 3—cytoplasmatic process of epithelial cell, 4—extracellular matrix, 5—collagen fibrils, 6—microvilli, 7—desmosome, 8—intermediate filaments. <b>R,R´,R´´,R´´´:</b> Ultrastructure of the dental stalk area at P14. 1—intercellular spaces between epithelial cells, 2—blood vessels, 3—nucleus of epithelial cell, 4—microvilli, 5—desmosome, 6—bundles of intermediate filaments, 7—keratohyaline granule, 8—degradated mitochondria