Please enable JavaScript.

Coggle requires JavaScript to display documents.

Histology Pt. 2, Reciprocal induction image, Tooth Germ, image - Coggle…

- - - - Cuboidal cells become columar cells due to reciprocal induction from the dental papilla
      - Differentiate all the way to the cervical loop to determine shape of the crown
    - - Cells become polarised, more golgi, rER, and mitochondria for secretion (Pre ameloblasts)
  - - - Basal lamina is resorbed and pre-ameloblasts become ameloblasts, then lay down the inital enamel matrix at DEJ
      - Matrix proteins synthesied in the rER, modifed in the golgi and secreted as early enamel, which mineralises very rapidly
      - No Tome's formed yet
    - - Ameloblasts retreat from DEJ and their distal ends form the Tome's process frorming the prismatic enamel
      - Enamel rod created at an angle to ameloblasts
      - One rod is formed by 4 ameloblasts (one for the head and three for the tail)
      - Crystalites are formed instantly, calcium is transported from the ectomesenchyme into the ameloblasts and into the enamel matic to form the hydroxyapetit crystals
      - Secretion ends when the tome's process retracts (lays down a prismless enamel)
  - - - Ruffeled 80% of the time
      - Pumps CaPO4 into the crystals for growth
      - Cycles between Ruffled and Smooth
    - - Removes water and proteins from the enamel
      - Smooth 20% of the time
  - - - Ameloblasts, OEE and SR collapse to become the reduced enamel epithelium which protects the from surrounding conntective tissue
    - - The overlying connective tissue is degraded during eruption
  - - - Accumulates during the secretory stage (90% of the proteins in the organic material)
    - - Crystal nulceation/growth
    - - cell adhesion and protein which stablises the amleoblsat
    - - loclaised at the DEJ
- - - - Mineralization occurs through fibroblasts pumping collagen fibers into the dentine
        
        Globular mineralization (fast)
        
        Linerar mineralization (slow)
- - - - Called neural plate
      - Edges thicken forming a neural groove
      - Neural folds continue to deep and eventually join to become the neural tube
      - Nueral crest cells devlope alongside along the nueral tube
        
        Neural crest cells eventually migrate to form the embryonic connective tissue (ectomesenchyme) of the facial skeletal muscle and sensory ganglia and neural cells
  - - - Bud Stage
        
        epithelium continues to develope and produces small buds that push down the underlying ectomesencyme
      - Cap Stage
        
        Epithelium resembles a cap - covering a ball of condensing ectomesencyme
        
        For pernament teeth in the incisor, canine or premolar arae an additional dental lamina will form
        
        Enamel Organ = the developing epeithelium
        
        Dental Papilla = condensing ecomesncyme, will become the dentine and pulp
        
        Dental follicle = "sac" forms the periodontal structures, and important for eruption
        
        Gubernacilar chord = connects the tooth germ to the outer envrionement
      - Bell Stage (early)
        
        Cell differeniation, cord is disentergrated and crown shape is determined (morphodiferentiation)
        
        Central cells = stellate reticulum
        
        OEE = Outer enamel epithelium
        
        IEE = Inner enamel epithelium
        
        Stratum intermedium (between IEE and Stellate reticulum)
        
        Cervical loop = joining of IEE and OCC
      - Bell Stage (late)
        
        Dentine begins (crown stage of development)
        
        Begins at the tips of the cusps due to signsal from the IEE
        
        Odontoblasts and pre-ameloblasts come into contact w/ IEE which initiates (reciprocal induction) their differeniation
        
        Odontoblasts move away laying down behind them dentine, at the same time Amelobalats are formed
      - Timing
        
        Primary teeth weeks 6-8
        
        Successional pernament Wk 20 and 10 months after birth
        
        Remaing molars week 20 and 5 years after birth (3rd molars)
      - Root Formation
        
        HERS (Hertwigs Eoitelum Root Sheath
        
        IEE cells initiate differentiation of dental papilla to form odontoblasts
        
        After root formation begins HERS disintergrates and the cells left behind form epithelial rest cells of Malassez
        
        Can contribute to cysts that occur in the PDL
- - - - Root formation
  - - - Enamel