Thursday, 7 January 2016

Latest Embryology Interview Questions and Answers

41. What is gastrulation? How during gastrulation are the first two germ layers formed? Which are these germ layers?
Gastrulation is the process through which a portion of the blastula wall undergoes invagination inside the blastocele forming a tube called archenteron (primitive intestine). The cells of the inner side of the tube form the endoderm (germ layer) and the cells of the outer side form the ectoderm (another germ layer). It is the beginning of the tissue differentiation in the embryonic development.

42. After the blastula stage what is the following stage of the embryonic development? How is the passage from blastula to the next stage called?
The blastula turns into gastrula in a process known as gastrulation.

43. After the morula stage what is the next stage? What is the morphological feature that defines that stage?
After passing the morula stage in which the embryo was a compact mass of cells, the next stage is the blastula stage. In the blastula stage, the compactness is lost and an internal cavity filled with fluid appears inside, the blastocele.

44. What are the cells produced in the first stage of the embryonic development called?
The cells that resulted from the cleavage (the first stage of the embryonic development) are called blastomeres. In this stage the embryo is called morula (similar to a “morus”, mulberry).

45. What is the cell division during the first stage of the embryonic development called? How is this stage characterized?
The cell division in the first stage of the embryonic developments is called cleavage, or segmentation. In this stage, mitosis occurs from the zygote forming the new embryo.

46. What are the four initial stages of the embryonic development?
The four initial stages of the embryonic development are the morula stage, the blastula stage, the gastrula stage, and the neurula stage.

47. What are the animal pole and the vegetal pole of the vertebrate egg?
The animal pole of a telolecithal egg is the portion of the egg with little vitellus, it is opposite to the vegetal pole that is the region where the yolk is concentrated.

48. What is the function of the vitellus in the vertebrate egg? How are these eggs classified according to the amount of vitellus within them?
Vitellus (yolk) is the nutritive material that accumulates in the cytoplasm of the egg (zygote) with the function of nourishing the embryo. According to the amount of vitellus in them, the vertebrate eggs are classified as oligolecithal (little yolk), centrolecithal, or heterolecithal (more yolk diffusely distributed) and telolecithal (more yolk concentrated in one end of the egg).

49. What is the cell division process directly related to the embryonic growth?
The embryonic growth depends directly on mitosis. Through this type of cell division, the zygote divides itself giving birth to a series of cells that by mitosis too compose differentiated tissues and organs until the formation of a complete individual.

50. 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).

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