Saturday, May 5, 2018

Hertwig's Epithelial Root Sheath- HERS

Hertwig's epithelial root sheath
  • It originates from the cervical portion of the enamel organ.
  • It plays an important role in determining shape length size and number of roots.
  • It is a double layer of cells which consists of outer enamel epithelium and inner enamel epithelium.
  • Root sheath extends around dental papilla and separates it from surrounding dental follicle all through except the Basil portion.
  • Inner enamel epithelial layer of root sheath influences the formation of odontoblast from the outer portion of the radicular dental papilla. 
  • These odontoblasts lead to the formation of the first layer of radicular dentin.

As the first layer of radicular dentin is laid down:
  • HERS loses its continuity 
  • The cells of the dental follicle or dental sac invade double layer of HERS 
  • Root sheath degenerates to form epithelial Islands

Therefore, it allows connective tissue of dental follicle to come in contact with newly formed radicular dentin. 

This causes differentiation of cementoblast from dental follicle which deposits cementum on newly formed radicular dentin.

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