mammalian cleavage: definition,pattern, importance and steps

1. sAMHIGGINBOTTOMuniversityof agriculture,TECHNOLOGYAND
sCiences
GROUPPROJECT OF DEVELOPMENTALBIOLOGY
BIOL-536
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Ankitasharma(17bslscfs015)
Anjalimishra(17bslscfs017)
Nutanprabha(17bslscfs018)
6 semester
LSCFS

2. CLEAVAGE in
mammals

3. • Cleavage
• Patterns of mammalian cleavage
• Importance of cleavage
• Early embryonic development
• Development step: cleavage and blastula.
CONTENT

4. Cleavage is a rapid series of mitotic
divisions that occur just after
fertilization.The process follows
fertilization, with the transfer being
triggered by the activation of a
cyclin-dependent kinase complex.
WHAT IS CLEAVAGE ?

5. Patterns of mammalian cleavage
The repeated cleavage furrows produce a number of
blastomeres which exhibit a specific pattern of
arrangement.
The following types of cleavage patterns are:-
• On the basis of cleavage furrow.
• On the basis of fate of germ layers.
• On the basis of arrangement of the cells.

6. Importance of cleavage
The critical reasons why cleavage is so
important:-
1. Generation of a large number of cells that
undergo differentiation and gastrulation to
organs
2. Increase in the nucleus /cytoplasmic ratio.
3.It converts a unicellular zygote into a
embryo.
4 . It brings about the distribution of cytoplasm
among the blastomere.

7. Mammalian
CLEAVAGE

8. Early embryonic development
four essential stages in early embryonic development:
1. Fertilization: the process of a single sperm cell combining with single egg
cell to form a zygote.
2. Cleavage: the first major phase of embryonic development,it gives rise to
blastomere.
3. Gastrulation: the dramatic rearrangement of cells in the blastula to create
the embryonic tissue layers.
4. Organogenesis: the process of organ and tissue formation via cell division
and differentiation.

10. Development step:cleavage and
blastula
• The mammalian oocyte is released from the ovary. Fertilization
occurs in the ampulla of the oviduct.
• Meiosis is completed at this time, and first cleavage begins
about 30 hours after fertilisation.
• The cilia in the oviduct push the embryo toward the uterus; the
first cleavages occur along this journey.

11. The first cleavage

12. • the second cleavage, one of the two blastomeres divides
meridionally and the other divides equatorially. This type of
cleavage is called rotational cleavage.
• In the third cleavage most other embryos is the marked
asynchrony of early cell division.
• In fourth cleavage , genome is activated during early cleavage,
and produces the proteins necessary for cleavage to occur.

14. • The fifth cleavage involves the phenomenon of
compaction,the blastomeres suddenly huddle together,
maximizing their contact with one another and forming a
compact ball of cells.
• The cells of the compacted 8-cell embryo divide to produce a
16-cell morula.The morula consists of a small group of internal
cells surrounded by a larger group of external cells.
• Most of the descendants of the external cells become the
trophoblast (trophectoderm) cells,it forms placenta.

15. • These cells generate the inner cell mass (ICM), which will give rise to
the embryo and its associated yolk sac, allantois, and amnion.
• By the 64-cell stage, the inner cell mass (approximately 13 cells) and
the trophoblast cells have become separate cell layers.
• During a process called cavitation, the trophoblast cells secrete fluid
into the morula to create a blastocoel.
• The inner cell mass is positioned on one side of the ring of
trophoblast cells . The resulting structure, called the blastocyst.
• Centrall located, inner cell mass or embryoblasts gives rise to
embryo.

17. References
• https//:Courses.lumenlearning.com
• https//:britanica.com
• Https//:biologydiscussion.com
• https//:chegg.com

18. THANK YOU