O segmentation type that the zygote will suffer is related to the amount of yolk accumulated in the egg. The greater the amount of yolk in the egg, the slower the zygote's segmentation.
You types of embryonic segmentation are: holoblastic or total segmentation, and meroblastic or partial segmentation.
Holoblastic or total segmentation it is the type of segmentation that occurs in the whole egg and is common in allecitos, oligolécitos and heterolécitos eggs. Holoblastic segmentation is divided into equal holoblastic, unequal holoblastic, and subequal holoblastic segmentation.
- Equal holoblastic segmentation: this type of segmentation occurs in alecite eggs and in some oligolectic eggs. It is characterized by the formation of eight equal blastomeres in the third cleavage.
- Uneven holoblastic segmentation: type of segmentation that occurs in all heterolecite eggs and in some oligolectic eggs. It is characterized by the formation of eight blastomeres of different sizes in the third cleavage. Larger blastomeres are called macromers; and the smallest, micromers.
- Subequal holoblastic segmentation: type of segmentation that occurs in isolocyte eggs, and is characterized by the formation of eight blastomeres that do not differ much from each other in size.
Due to the difference in calf distribution, the meroblastic segmentationpartial divides into discoidal and superficial.
- Discoidal meroblastic segmentation: cleavages occur only in the region of the cell that does not have a yolk, called the cicatricle. This type of cleavage occurs in telolocyte eggs.
- Superficial meroblastic segmentation: Occurs in centrolocyte eggs. In this type of segmentation, embryonic cells are found on the surface of the egg.
Paula Louredo
Graduated in Biology
Source: Brazil School - https://brasilescola.uol.com.br/biologia/tipos-segmentacao-embrionaria.htm
