Thursday 7 January 2016

Embryology Interview Questions and Answers for freshers pdf free download

11. How is the mesoderm (third germ layer) of triploblastic animals formed?
The mesoderm appears from differentiation of endodermal cells that cover the dorsal region of the archenteron.

12. What are the three types of germ layers that form tissues and organs in animals?
The three germ layers are the ectoderm, the mesoderm, and the endoderm.
Image Diversity: germ layers

13. How are animals classified according to the germ layers present in their embryonic development?
Cnidarians are diploblastic, i.e., they present only endoderm and ectoderm. With the exception of poriferans, all remaining animals are triploblastic. Poriferans do not present differentiated tissue organization and so they do not classify regarding germ layers (although sometimes they are mentioned as diploblastic).

14. How does the embryo turn from gastrula into neurula? How is the neural tube formed? What is the embryonic origin of the nervous system in vertebrates?
The neurula stage is characterized by the appearing of the neural tube along the dorsal region of the embryo. The growing of mesoderm in that region induces the differentiation of ectodermal cells just above. These cells then differentiate forming the neural tube. Therefore, the origin of the nervous system is the ectoderm (the same germ layer that gives birth to the skin).
Image Diversity: neurula

15. What is notochord? How is this structure formed?
Notochord is a rodlike structure that forms the supporting axis of the embryo and gives birth to the vertebral column in vertebrates. It is formed by differentiation of mesodermal cells.

16. What is coelom? To which structures do coeloms give birth? Are all animals coelomate?
Coeloms are cavities delimited by mesoderm. Coeloms originate the cavities where the internal organs of the body are located, like the pericardial cavity, the peritoneal cavity, and the pleural cavity. Besides coelomate animals, there are acoelomate animals, like platyhelminthes, and pseudocoelomate animals, like nematodes.
Image Diversity: coelom

17. What is the germ layer from which the coeloms originate?
The coeloms are originated from mesoderm.

18. What are pleura, pericardium, and peritoneum?
Pleura are the membrane that covers the lungs and the inner wall of the chest; pericardium is the membrane that covers the heart; peritoneum is the membrane that covers most organs of the gastrointestinal tract and part of the abdominal cavity. All these membranes delimit coeloms (internal cavities).
Image Diversity: pleura pericardium peritoneum

19. After the neurula stage and from its ventral portion to the dorsal how can the morphology of the embryo be described?
In a schematic longitudinal section of the embryo after the neurula stage, the outermost layer of cells is the ectoderm. In the ventral region comes the archenteron tube formed of endodermal cells. In both sides of the embryo, coeloms delimited by mesoderm are present. In the central region above the archenteron and in the middle of the coeloms there is the notochord. In the dorsal region just above the notochord lies the neural tube.

20. What are somites?
Somites are differentiated portions of mesodermal tissue longitudinally distributed along the embryo. The somites originate the muscle tissue and portions of the connective tissues.
Image Diversity: somites


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