In
tooth development
Tooth development or odontogenesis is the complex process by which teeth form from embryonic cells, grow, and erupt into the mouth. For human teeth to have a healthy oral environment, all parts of the tooth must develop during appropriate st ...
, the enamel knot is a localization of
cells
Cell most often refers to:
* Cell (biology), the functional basic unit of life
Cell may also refer to:
Locations
* Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...
on an
enamel organ
The enamel organ, also known as the dental organ, is a cellular aggregation seen in a developing tooth and it lies above the dental papilla. The enamel organ which is differentiated from the primitive oral epithelium lining the stomodeum.The enam ...
that appear thickened in the center of the
inner enamel epithelium
The inner enamel epithelium, also known as the internal enamel epithelium, is a layer of columnar cells located on the rim nearest the dental papilla of the enamel organ in a developing tooth. This layer is first seen during the cap stage, in wh ...
. The enamel knot is frequently associated with an
enamel cord The enamel cord, also called enamel septum, is a localization of cells on an enamel organ that appear from the outer enamel epithelium to an enamel knot. The function of the enamel cord and the enamel knot is not known, but they are believed to p ...
. It is formed in the cap stage and undergoes apoptosis in the bell stage.
The enamel knot as signaling center
The enamel knot is a signaling center of the tooth that provides positional information for tooth morphogenesis and regulates the growth of
tooth cusps. The enamel knot produces a range of molecular signals from all the major signaling families, such as Fibroblast Growth Factors (FGF), Bone morphogenetic proteins (BMP), Hedgehog (Hh) and Wnt signals. These molecular signals direct the growth of the surrounding epithelium and
ectomesenchyme
Ectomesenchyme has properties similar to mesenchyme. The origin of the ectomesenchyme is disputed. It is either like the mesenchyme, arising from mesodermic cells, or conversely arising from neural crest cells. The neural crest is a critical group ...
.
Primary and secondary enamel knots
The primary enamel knot forms at the tip of the bud during the cap stage of tooth development. This primary enamel knot undergoes apoptosis and disappears. Later, secondary enamel knots appear that regulate the formation of the future cusps of the teeth.
[Salazar-Ciudad, I., & Jernvall, J. (2010-03-25).]
"A Computational Model of Teeth and the Developmental Origins of Morphological Variation."
''Nature'', vol. 464, pp. 583-586.
References
*Cate, A. R. Ten. (1998). ''Oral Histology: Development, Structure, and Function'', 5th ed. .
*Ross, M. H., Kaye, G. I., & Pawlina, W. (2003). ''Histology: A Text and Atlas'', 4th edition. {{ISBN, 0-683-30242-6.
*Vaahtokari A., Aberg T., Jernvall J., Keranen S., Thesleff, I (1996). "The Enamel Knot as a Signaling Center in the Developing Mouse Tooth. ''Mech Dev''. vol. 54, no. 1, pp. 39-43.
*Jernvall, J., Kettunen, P., Karavanova, I., Martin, L. B., Thesleff, I. (1994). "Evidence for the Role of the Enamel Knot as a Control Center in Mammalian Tooth Cusp Formation: Non-dividing Cells Express Growth Stimulating Fgf-4 Gene." ''Int. J. Dev. Biol.'' vol. 38, pp. 463-469.
Parts of tooth