Embryonic-Cell-Division-Cleavage-and-Its-Types.pptx

This presentation provides a comprehensive overview of embryonic cell division, focusing on the process of cleavage and the different types observed in various organisms. It explains the stages, patterns, and significance of cleavage in early development, making it a useful resource for students studying developmental biology, cell biology, or related life sciences.

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2. A Presentation on: Embryonic Cell Division Process: Cleavage and Cleavage Types 2

3. Presented To Dr. MD. Mofizur Rahman Associate Professor Department of FIMS NSTU Sonapur 3814, Noakhali. Presented By Jannatul Ferdous Shefa (BKH2202022F) Kamibul Alam Kabbo (MUH2202024M) Imam Hossain (MUH2202025M) Misbah Mahbuba Minha (BKH2202027F) Sumaiya Rahnuma Khan (BKH2202029F) Rahee (BKH2202030F) 3

4. Embryonic cell division Process: Cleavage and Cleavage Types What is embryonic cell division? Embryonic cell division refers to the rapid and coordinated series of cell divisions that occur after fertilization, leading to the formation of a multicellular organism. It's the foundation of development, transforming a single cell zygote into a complex embryo with specialized tissues and organs. 4

5. The process of embryonic cell division 1. Cleavage : This is the initial phase, where the zygote undergoes repeated mitotic divisions without significant growth. The resulting cells, called blastomeres, become progressively smaller with each division. 2. Blastula formation : As cleavage continues, the blastomeres arrange themselves into a hollow sphere called a blastula. Different organisms display distinct cleavage patterns, like radial, spiral, or rotational. 3. Gastrulation: This marks the transition from a simple ball of cells to an embryo with differentiated layers. Here, cell movements and rearrangements establish the three primary germ layers (ectoderm, mesoderm, and endoderm), paving the way for organ development. 5

6. Significance Growth and development: Embryonic cell division is essential for generating the millions of cells needed to build the embryo's diverse structures. Cellular differentiation: As divisions progress, cells start expressing different genes, leading to the formation of distinct cell types with specific functions. Patterning and morphogenesis: The spatial and temporal control of cell division helps establish the overall body plan and organ positioning within the embryo 6

7. CLEAVAGE The term "cleavage" in embryology describes the quick succession of cell divisions that take place during an embryo's early development after fertilisation. The single-celled zygote (fertilised egg) becomes a multicellular ball of cells known as a blastula during this vital process.. The term cleavage was observed Swammerdam in 1738 at Frog’s egg. The cleavage stage cells are called blastomeres. In most species, the rate of cell division & the placement of the blastomere are controlled by the proteins & mRNA , stored in the oocyte by the mother. Cleavage begins soon after the fertilization end shortly ,the stage where the embryo achieves a new balance between nucleus & cytoplasm. 7

8. Cleavage in the egg can occur through different planes. Meridional plane : When a cleavage furrow passes through the center of the egg or median axis and bisects both animal and vegetal poles and the egg is divided into two equal halves, is called the meridional plane of cleavage. The axis between the center of the animal and the vegetal pole is a median axis. Equatorial plane : The line of division is at right angle to the median axis and the cleavage furrow divides the egg in the middle between both animal and vegetal poles. 8

9. Vertical plane: The cleavage furrow does not pass through the center of the median axis instead located on either side of the median plane and the cells formed are of unequal size. Latitudinal plane : This plane is very similar to equatorial and the cleavage furrow is present on either side of the equatorial plane in the cytoplasm. It is also known as horizontal or transverse cleavage. Animal pole: The pole of the egg that has less yolk is termed as animal pole. Vegetal pole: The pole of the egg which is rich in yolk is termed a vegetal pole. 9

10. Significance of Cleavage Regulating Nuclear-Cytoplasmic Ratio Establishing Cell Lineages and Fate : Creating a Multicellular Foundation Initiating Embryonic Communication: 10

11. Types of Cleavage: ON THE BASIS OF FATE OF GERM LAYERS 1. Determinate Cleavage 2. Indeterminate Cleavage ON THE BASIS OF CLEAVAGE FURROW 3. Holoblastic Cleavage 4. Meroblastic Cleavage 11

12. ON THE BASIS OF GERM LAYER DETERMINATE CLEAVAGE -Also called mosaic cleavage -Mostly found in protostomes -If these cells are separated from each other ,they will die & they have no potential to develop an organism on its own Examples of organisms with determinate cleavage include: •Annelids (worms) •Mollusks (snails, clams) •Echinoderms (sea stars) 12

13. ON THE BASIS OF GERM LAYER INDETERMINATE CLEAVAGE - This is also called regulative cleavage. -A cell can only be indeterminate if it has a complete set of undisturbed features. -If these cells are separated from each other , each has the potential to develop into an entire organism on its own. - It occurs in most of the deuterostomes . Examples of organisms with indeterminate cleavage include: -Amphibians (frogs, toads), -Echinoderms (some species) 13

14. ON THE BASIS OF CLEAVAGE FURROW HOLOBLASTIC CLEAVAGE In holoblastic cleavage , the zygote & blastomeres are completely divided during the cleavage,so the number of blastomeres doubles with each cleavage. There are four types of holoblastic cleavage- -Bilateral holoblastic - Radial holoblastic - Spiral holoblastic - Rotational holoblastic 14

15. HOLOBLASTIC CLEAVAGE Bilateral Cleavage -First cleavage divide the zygote into two right and left cells,then each right and left side cleave separately on right and left making mirror images of embryo on right and left sides is bilateral holoblastic cleavage. EX- Tunicates, Amphibians 15

16. HOLOBLASTIC CLEAVAGE Radial Cleavage -It is one of the simplest cleavage patterns in which the successful division planes are at 90° relative to each other. Thus this cleavage results in daughter cells that are located exactly on top of one another. Found in Deuterostomes. EX- Echinoderms (SEA-URCHIN mainly) 16

17. HOLOBLASTIC CLEAVAGE Spiral Cleavage - The cleavage which is at oblique to animal-vegetal axis and make a spiral look. The resulting daughter cells are not located exactly on top of each other. Instead, the blastomeres are organised spirally around the embryo's pole-to-pole axis. This type is characteristic of annelids, mollusks, and flatworms. 17

18. HOLOBLASTIC CLEAVAGE Rotational Cleavage - Zygote divide into two blastomere. One blastomere divides asymmetrically to give rise one founder cell and one stem cell, while other blastomere divides equatorially to produce normal differentiating cells. Stem cell again divide meridionally to repeat the pattern. This kind of asymmetric cleavage is termed as rotational. This type is seen in mammals and nematodes 18

19. ON THE BASIS OF CLEAVAGE FURROW Meroblastic Cleavage -This type occurs when only part of the zygote divides, typically due to the presence of a large amount of yolk concentrated at one end. The cleavage furrows do not extend through the yolk-filled region. Meroblastic cleavage is also categorized into subtypes: 1. Discoidal Cleavage 2. Superficial Cleavage 19

20. MEROBLASTIC CLEAVAGE Discoidal Cleavage - Cleavage furrows extend only through the disc-shaped cytoplasmic cap at the animal pole of the zygote, leaving the yolk mass undivided. This pattern is seen in birds, reptiles, and some bony fish 20

21. MEROBLASTIC CLEAVAGE Superficial Cleavage -Cleavage that occcurs in the periphery of cytoplasm in centrolethical eggs due to large central yolk is superficial cleavage. -This type is observed in insects and some arachnids . 21

22. Cleavage VS Cell Division 22

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