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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 ...
Intermediate mesoderm or intermediate mesenchyme is a narrow section of the mesoderm (one of the three primary germ layers) located between the paraxial mesoderm and the lateral plate of the developing embryo. [1] The intermediate mesoderm develops into vital parts of the urogenital system (kidneys, gonads and respective tracts).
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.
During the third week, the paraxial mesoderm is organized into segments. If they appear in the cephalic region and grow with cephalocaudal direction, they are called somitomeres. If they appear in the cephalic region but establish contact with the neural plate, they are known as neuromeres, which later will form the mesenchyme in the head. The ...
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 AEF potentially functions as an inhibitor to fin outgrowth since removing the AEF results in the formation of a new AER and subsequently a new AEF. In addition, repeated AF removal leads to excessive elongation of the fin mesenchyme, potentially because of prolonged exposure of AER signals to the fin mesenchyme. [16]
The genital ridge initially consists mainly of mesenchyme and cells of underlying mesonephric origin. Once oogonia [clarification needed] enter this area they attempt to associate with these somatic cells. Development proceeds and the oogonia become fully surrounded by a layer of cells (pre-granulosa cells).