# initiation stage
- 6-7 week
- In prenatal development
In 6 week
- oral epithelium lines primitive oral cavity from ectoderm
يسمى هذا النسيج ectoepithelium
لانه ياتي من ال ectoderm
تحت النسيج الخارجي نجد النسيج mesenchymal tissue المشتق من الطبقة الوسطى
- this ectoepithelium found at the outer surface of stomodium
معلومة خارجية
The stomodeum, also called stomatodeum or stomatodaeum, is a depression between the brain and the pericardium in an embryo, and is the precursor of the mouth and the anterior lobe of the pituitary gland.
Now this ectoepithelium is called primary epithelium band
in the 7 weeks the primary epithelium band grows and invaginates deep in the mesenchymal (Invagination is the infolding of one part within another part of a structure,[1] a folding that creates a pocket.)
Every primary epithelium is divided into:-
lingual - vestibular lamina
buccal- dental lamina
معلومة خارجية
The vestibular lamina also termed as lip furrow band is a proliferation of cells into ectomesenchyme tissue.[1] Responsible for the formation of the vestibule (the space bordered by the junction of the gingiva and the tissue of the inner cheek), the vestibular lamina is usually contrasted with the dental lamina, which develops concurrently and is involved with developing teeth. Both the vestibular lamina and the dental lamina arise from a group of epithelial cells, called the primary epithelial band.
Explanation:- The vestibular lamina develops at 6th week of the intrauterine life as a result of proliferation of the primitive ectoderm that lines the primitive oral cavity labial and buccal to the dental lamina.[2] The cells enlarge and then degenerate to form a cleft that separates the lips and cheeks at one side from the developing jaws and teeth at the other side. This cleft is the oral vestibule
#Bud stage
-8th week
- Prenatal period
- In dental lamina cells proliferate (grow) to form bud or tooth germ described as oral mass.
- this tooth bud pentetrate mesenchyme - الطبقة الوسطى
في هذه المرحلة يحصل فقط proliferation
#Cap stage
- 9-10 the week
- Prenatal period
- for primary dentition الاسنان اللبنية
- tooth bud keeps proliferation unequally (نمو غير متساوي) lead to formation of cap shaped structure (شكل الكوفية ) with deep depression attached to dental lamina called enamel organ
- formation of dental papilla after condensation of deeper portion of mesenchymal under/along enamel orgin
- basement membrane seperates enamel from dental papilla,
this basement membrane will be called Dento enamel junction DEJ in future tooth.
After formation of dental papilla, the dental sac or follicle is formed after condensation of mesenchyme
- the cap stage is of most importance because of the formation of 3 important embryological structures
1- Enamel organ
2- Dental papilla
3- Dental sac
1- Enamel organ comes from ectoderm and gives us enamel
2- Dental papilla comes from mesenchyme and gives us dentin and pulp
3- Dental sac comes form mesenchyme and gives us periodentum
periodontum is the supporting tissue like
a- cementum
B- periodontal ligament
c- alveolar bone
في مرحلة ال cap stage يحصل
Proliferation + differentiation+ morphogensis
# Bell stage
- 11 - 12th week
- Prenatal development
- during bell stage، cells keep growing to change in shape from cap to bell shape
- cell types formed in this stage
1- outer enamel epithelium OEE = support + enamel formation
2- stellate reticulum = nourishment + enamel formation
3- stratum inter medium = enamel formation
4- inner enamel epithelium = enamel formation
في هذه المرحلة يحصل
Proliferation + differentiation + morphogensis
# Apposition
during this stage, enamel from enamel organ, dentin from dental papilla and cementum from dental sac are secreted successively into layers as a matrix which is partially calcified as a framework for maturation latter calcification
في هذه المرحلة تحصل عملية
Proliferation + induction
# Maturation
- dental tissue is fully mineralized
Ameloblast are derived from IEE inter enamel epithelium
في هذه المرحلة يحصل maturation
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