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what plays an important role in defining the site specific nature of cell differentiation snd proliferation?

Interactions between Epithelial cells and connective tissue (mesenchyme) cells (fibroblasts) in the oral mucosa


what are these interactions?

both dynamic and reciprocal


what is connective tissue?

-Structural portions of body
-Hold the cells of the body together
-Framework or matrix for the body.
-Structural molecules collagen and elastin
(few cells, lots of matrix)


what is the mesenchyme?

-Mesodermal origin
- loosely packed
-unspecialized cells
- gelatinous ground substance from which connective tissue, bone cartilage and the circulatory and lymphatic systems develop


what differentiates in tooth to make enamel?



what are the 4 fundamental aspects of developmental biology?

-Proliferation/Growth-size : how cells divide
-Pattern formation: is the process by which cells in a developing embryo acquire identities that lead to a well ordered spatial pattern of cell activities.


what is sequentially?

timing of events


what is dynamic?

happens quickly


what is reciprocal?

one in control then the other


what are the 2 general types of phenomena in tissue interactions?



Describe instructive.

the ability of one tissue to determine specific patterns of morphogenesis and differentiation that will develop in an associated tissue


Describe permissive (or facilitative).

the ability of an interacting tissue to provide certain conditions that is necessary for its committed partner tissue to progress to full expression of its pre-determined phenotype


what are the 4 types of interactions used in experimental work?

-Homotypic: same time, place and species.
-Heterotypic: unrelated usually same time and species.
-Heterochronic: same type and species but different time.
-Heterospecific: similar areas but different species


Describe organogenesis.

-Secondary inductions
-Patterning-right place
-Organ rudiment- morphogenesis and proliferation
-Organ specific structures- differentiation


Name the stages of development of organogenesis.

-epithelial placode
-adult organ (tooth)


where do first signals directing organogenesis come from?



Name some experiments in cell-cell interactions.

-Early work on tissue recombination
-Organ culture using filters
-Organ culture using Trowell dish
-Bead implantation
-In situ hybridisation


what happens in tooth development (mouse)?

day 9/10-initation
day 12- bud
day 14- cap
day 16-bell


what is differentiation of cell types during tooth development?

-cells become more specialised
-Amorphous blobs-
-Various stages to get to final structures.
-These are dynamic, reciprocal and sequential in nature


During differentiation of cell types, what interacts to initiate signal?

mesenchyme and epithelium


What are cytokines and what happens during development?

-Small molecules transmitted over small distances.
-Drive all processes of tooth development at least 30 known in tooth development.
-Receptors and signalling.
-RNA synthesis of other cytokines and ECM molecules


What is the Extracellular matrix and what happens in development?

-Important in morphogenesis and differentiation.
-Adhesion, migration, proliferation, polarisation and differentiation.
-Expression of type I, III, IV collagens, laminin, various proteoglycans- basement membrane of developing tooth
-Changes in fibronectin, tenascin, type I and type III collagen and syndecan.
-Changes in integrin expression especially alpha v beta 5.
-Need intact basement membrane for differentiation of mesenchyme to odontoblast


Describe the stages in oral development.

-Interaction between oral ectoderm and mesoderm.
-Lots of epithelial mesenchymal interactions in development; salivary glands, palate formation, tongue and tooth development.
-In normal homeostasis these interactions continue in the adult


what happens if you take out TGF B-3 in mice?

Growth factor is taken out so gene is not expressed and palatal shelfs haven't fused so mouse develops cleft palate