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Mesenchyme (/ ˈ m ɛ s ə n k aɪ m ˈ m iː z ən-/ [1]) is a type of loosely organized animal embryonic connective tissue of undifferentiated cells that give rise to most tissues, such as skin, blood or bone. [2] [3] The interactions between mesenchyme and epithelium help to form nearly every organ in the developing embryo. [4]
Epithelial and mesenchymal cells differ in phenotype as well as function, though both share inherent plasticity. [2] Epithelial cells are closely connected to each other by tight junctions, gap junctions and adherens junctions, have an apico-basal polarity, polarization of the actin cytoskeleton and are bound by a basal lamina at their basal ...
The mesenchyme, through FGF10 secretion, is involved in a positive feedback loop with the AER, through FGF8 secretion. FGF8 – Secreted by the AER cells. Acts upon the mesenchymal cells, to maintain their proliferative state. Also induces the mesenchymal cells to secrete FGF10, which acts through WNT3A to sustain the AER's expression of FGF8.
The face and neck development of the human embryo refers to the development of the structures from the third to eighth week that give rise to the future head and neck.They consist of three layers, the ectoderm, mesoderm and endoderm, which form the mesenchyme (derived form the lateral plate mesoderm and paraxial mesoderm), neural crest and neural placodes (from the ectoderm). [1]
The zone of polarizing activity (ZPA) is an area of mesenchyme that contains signals which instruct the developing limb bud to form along the anterior/posterior axis. Limb bud is undifferentiated mesenchyme enclosed by an ectoderm covering. Eventually, the limb bud develops into bones, tendons, muscles and joints.
The limb bud remains active throughout much of limb development as it stimulates the creation and positive feedback retention of two signaling regions: the AER and its subsequent creation of the zone of polarizing activity (ZPA) with the mesenchymal cells. [5]
Also induces the mesenchymal cells to secrete FGF10, which acts through WNT3A to sustain the AER’s expression of FGF8. WNT3A: Acts as an intermediate in the positive feedback loop between the AER and limb mesenchyme. Activated by FGF10 expression, activates FGF8 expression. Shh: [18] [19] Secreted by the ZPA in the limb bud mesenchyme ...
The prechordal mesenchyme proliferates laterally over the junction of the dorsal aorta and first aortic arch on each side. Gilbert P.W., (1957) STAGE 11 The prechordal plate contributes largely to the premandibular condensation and the mesenchyme of the heart such that little is seen in the median plane at this stage.