From Surf Wiki (app.surf) — the open knowledge base

Epithelial root sheath

Cells which initiate dentin formation in a developing tooth

Summary

Cells which initiate dentin formation in a developing tooth

Field	Value
Name	Epithelial root sheath
Latin	vagina epithelialis radicis
Image	Hertwig's epithelial root sheath.png
Caption	(1) The HERS, (2) ERM, (3) Dental follicle, (4) cementoblasts, (5) periodontal ligament, (6) alveolar cells, (7) bone, (8) odontoblasts.

The Hertwig epithelial root sheath (HERS) or epithelial root sheath is a proliferation of epithelial cells located at the cervical loop of the enamel organ in a developing tooth. Hertwig epithelial root sheath initiates the formation of dentin in the root of a tooth by causing the differentiation of odontoblasts from the dental papilla. The root sheath eventually disintegrates with the periodontal ligament, but residual pieces that do not completely disappear are seen as epithelial cell rests of Malassez (ERM). These rests can become cystic, presenting future periodontal infections.

Structure

Hertwig epithelial root sheath is derived from the inner and outer enamel epithelium of the enamel organ.

Function

The sheath is also responsible for multiple or accessory roots (medial growth) and lateral or accessory canals in the root (break in epithelium). It is controversial, but HERS may be involved in cementogenesis and the secreting of cementum, or that HERS-derived products might be related to enamel-related molecules, and that these proteins might initiate acellular cementum formation.

Other animals

While in mammals the HERS is rather a transient structure, in amphibians it is more or less a permanent one. Here the root epithelium does not fenestrate like in mammalians. Within vertebrates 3 distinct stages of HERS development can be observed.

In teleosts and chondrichthyans no HERS or root is really formed, and tooth development is restricted to crown development. An inflexible joint is formed between the tooth and the bone at the apical end of the tooth where the epithelium remains open.
In amphibians and non-crocodilian reptiles a continuous root sheath or HERS is formed without fragmentation of the epithelium. Once again a rather rigid connection between bone and tooth is formed at the apical end of the tooth where no epithelium is present.
In crocodilians and mammals the HERS is a transient structure and fragments to form the epithelial cell rests of Malassez. Through the gaps in the root epithelium elements of the periodontal ligament can migrate and form a flexible connection between bone and root.

History

Hertwig epithelial root sheath was not discovered in any mammalian species. Instead this epithelial structure was discovered by Oskar Hertwig in 1874 in an amphibian (see notes below for further discussion in other animals).

References

Hertwig, O. (1847) Über das zahnsystem der amphibien und seine bedeutung für die genese des skelets der mundhöhle. Arch. Mikrosk. Anat. EntwMech. 11 (suppl): 55–56

References

Ten Cate's Oral Histology, Nanci, Elsevier, 2013, p. 166
Illustrated Dental Embryology, Histology, and Anatomy, Fehrenbach and Popowics, Elsevier, 2026, p. 70-73
Ten Cate's Oral Histology, Nanci, Elsevier, 2013, p. 174
(May 2006). "Evolution and development of Hertwig's epithelial root sheath". Dev. Dyn..

Wikipedia Source

This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page.

tooth-development

Want to explore this topic further?

Ask Mako anything about Epithelial root sheath — get instant answers, deeper analysis, and related topics.

Research with Mako

Free with your Surf account

Content sourced from Wikipedia, available under CC BY-SA 4.0.

This content may have been generated or modified by AI. CloudSurf Software LLC is not responsible for the accuracy, completeness, or reliability of AI-generated content. Always verify important information from primary sources.

Report