What is the embryological origin of the transition zone?
A- Mesoderm***
B- Ectoderm
C- Endoderm
D- Mullerian duct
E- Mesonephric duct
Answer A:
Transition zone arises from mesoderm, peripheral zone arises from endoderm and central zone appears to be embryologically distinct possibly mullerian in origin.
The mesoderm, as opposed to the endoderm and the ectoderm, is the intermediate cell sheet of the triploblastic metazoan embryo that develops at the time of gastrulation. Only Bilaterians have it, poriferous (sponges) and cnidarians (jellyfish, corals, hydra, sea anemones, etc.) are deprived of it. On the other hand, they have a mesoglea, which is not an embryonic leaflet but a cell-poor tissue with a large extracellular matrix.
The cells that derive from the mesoderm form all or part of the internal organs with the exception of the nervous system (derived from the ectoderm), and organs of the digestive and respiratory systems (from the endoderm). Thus, in the Cordés, the mesoderm gives birth:
To the notochord (or chord, or axial mesoderm), regressing in humans and whose remnants form part of the nucleus proposed.
Para-axial mesoderm, giving it metamerized somites which in turn give rise to vertebrae and ribs (by the sclerotome), to skeletal muscles of the back (through the myotome) and to the connective dermis (by the dermatome);
At the intermediate mesoderm which gives it the kidneys (pro-, meso-, metanephros), the medulla of the gonads, the genital tract, and the ureters.
At the lateral mesoderm divided into somatopleura and splanchnopleure, between the two is created a cavity, the intraembryonic coelom, which fuses temporarily with extraembryonic coelom. During plication, the intraembryonic coelome closes, becomes a closed cavity and surrounds the viscera, forming notably the serosa and the mesentery:
Somatopleure, blade in contact with the ectoderm, giving bones and limb tendons (derived from mesenchymal cells and adrenal cortex.
Splanchnopleure, a blade in contact with the endoderm, giving blood vessels and blood cells, as well as visceral muscles, pericardium, pleura, myocardium and endothelium (which constitute the circulatory system).
Diagram showing mesoderm after delimitation (embryo closure)
Mesoderm also limits serous cavities (or coelomic cavities) of mesoblastic origin.
The mesoderm is thus the embryonic leaflet that produces a large part of the connective tissues (the majority of bones, the dermis ...), muscle tissue and the chord.
A- Mesoderm***
B- Ectoderm
C- Endoderm
D- Mullerian duct
E- Mesonephric duct
Answer A:
Transition zone arises from mesoderm, peripheral zone arises from endoderm and central zone appears to be embryologically distinct possibly mullerian in origin.
The mesoderm, as opposed to the endoderm and the ectoderm, is the intermediate cell sheet of the triploblastic metazoan embryo that develops at the time of gastrulation. Only Bilaterians have it, poriferous (sponges) and cnidarians (jellyfish, corals, hydra, sea anemones, etc.) are deprived of it. On the other hand, they have a mesoglea, which is not an embryonic leaflet but a cell-poor tissue with a large extracellular matrix.
The cells that derive from the mesoderm form all or part of the internal organs with the exception of the nervous system (derived from the ectoderm), and organs of the digestive and respiratory systems (from the endoderm). Thus, in the Cordés, the mesoderm gives birth:
To the notochord (or chord, or axial mesoderm), regressing in humans and whose remnants form part of the nucleus proposed.
Para-axial mesoderm, giving it metamerized somites which in turn give rise to vertebrae and ribs (by the sclerotome), to skeletal muscles of the back (through the myotome) and to the connective dermis (by the dermatome);
At the intermediate mesoderm which gives it the kidneys (pro-, meso-, metanephros), the medulla of the gonads, the genital tract, and the ureters.
At the lateral mesoderm divided into somatopleura and splanchnopleure, between the two is created a cavity, the intraembryonic coelom, which fuses temporarily with extraembryonic coelom. During plication, the intraembryonic coelome closes, becomes a closed cavity and surrounds the viscera, forming notably the serosa and the mesentery:
Somatopleure, blade in contact with the ectoderm, giving bones and limb tendons (derived from mesenchymal cells and adrenal cortex.
Splanchnopleure, a blade in contact with the endoderm, giving blood vessels and blood cells, as well as visceral muscles, pericardium, pleura, myocardium and endothelium (which constitute the circulatory system).
Diagram showing mesoderm after delimitation (embryo closure)
Mesoderm also limits serous cavities (or coelomic cavities) of mesoblastic origin.
The mesoderm is thus the embryonic leaflet that produces a large part of the connective tissues (the majority of bones, the dermis ...), muscle tissue and the chord.
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Urology