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The amazing Cell

ali rumayh

on 19 February 2011

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Transcript of Ameloblast

Ameloblast Sunday 20 - 2 - 2011 Students :
Part 1. Ali Rumayh
Part 2. Ahmad Mhrol
Part 3. Abdulaziz Onizy Supervisor :
Dr. Hani Daas The Amazing Cell *Mention the Role of Ameloblasts on Formation of Enamel.
*Describe The Life Cycle of Ameloblasts.
*Know The Secretory Products of Ameloblats.
*Show The Effects of Ameloblasts on Dentin Formation.
*Understand the Modern way of Describing Ameloblasts Stages. Objectives: * present only during tooth development.
Responsible for Amelogenesis : the formation of enamel on teeth. * Secrete the organic and inorganic structures ,which will mineralize to form enamel on teeth.
Protect enamel from injury. - Enamel is one of the 4 major tissues which make up the tooth.
- It is the hardest and most highly mineralized substance in the human body.
- It contains organic + inorganic materials + water * The secretory ends of the ameloblast are in a six-sided pyramid-like projections known as the Tomes' processes. - Tomes' process present onley in Formative (secretory) stage. * Ameloblasts are derived from oral epithelium tissue of
ectodermal origin. They differentiate from the
ectomesenchymal cells of the dental papilla. * The ameloblasts provide effects on Dentin formation and will only become fully functional after the first layer of dentine has been formed by odontoblasts. According to their function, can be divided into six stages:
1- Morphogenetic stage.
2- Organizing stage.
3- Formative stage.
4- Maturative stage.
5- Protective stage.
6- Desmolytic stage. 1- Morphogenetic phase
( pre secretory stage) Before the ameloblasts are fully differentiated to produce the enamel,
the IEE determine the amelodentinal junction, which establishes the morphology of the crown. The cells are short columnar.
Large , oval , centralized nuclei.
Golgi apparatus and centrioles are located in the proximal (basal) end.
Mitochondria are disperse.
The IEE separated from the dental papilla by a basement membrane.
The adjacent pulpal layer is a cell-free zone. 2- Organizing Stage The IEE interact with the adjacent ectmesenchymal cells which differentiate into odontoblasts.
The IEE cells become longer.
The cell free zone disappears.
Alteration in cell polarity.
Golgi apparatus and centrioles migrate to the distal end.
Mitochodria present in the proximal end. The formation of dentin by the odontoblasts begins by the end of the organizing (differentiation )phase. 3- Formative Stage Begins after the first layer of dentin has been formed.
No cone formation (Tomes Process) so, The first enamel matrix is called rodless or aprismatic enamel. (organic layer) - After the deposition of dentin, the basement membrane supporting the inner enamel epithelium disintegrates
- Inner dental epithelial cells become differentiated into ameloblasts & initiate their formative stage
- Enamel formation is initiated with the formation of the first increment of enamel matrix.
- Then it mineralized with the deposition of the hydroxyapatite crystals in a parallel manner & perpendicular on Dentin surface. the
start as
calcification 3- Formative Stage cont. - As this first increment of enamel is formed, the ameloblasts begin to move away from the dentin surface (outward), and, as they do, each cell forms a conical projection called Tomes process.
- The Enamel matrix secretion is increased , then mineralized. References :
Ten Cate`s Oral Histology , seventh edition.
Contemporary Orthodontics , fourth edition.
Textbook of Orthodontic. Thanks to my friends (Mohamad zunaidy , Mohamad Saab) O
S -two step process:1st,produces a mineralized enamel – 30% mineralized-.
2nd,involves an additional mineral content + the removal of organic material and water –96%mineralization- Life Cycle of The Ameloblast The fundamental organizational units of enamel are RODS and INTERRODs .
*The rods are a long,thin structures extending from the DEJ to the surface of enamel. It is formed by the Tomes process of Ameloblast , become more aligned as they move away from DEJ , built from closely packed hydroxyapatite crystals.
*The calcium phosphate unit has hexagonal symmetry that are stacked together as Rod or Interrod enamel. (proteins: enamelin and amelogenin)
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