Cleavage & Blasulasi

CLEAVAGE & FORMATION OF THE BLASTULA
CLEAVAGE
 karyokinesis
 cytokinesis.

CONNECT THAT WORDS
 CLEAVAGE
 BLASTOMERE
 BLASTULA
 BLASTOCOEL
TYPES OF CLEAVAGE
 Vertical or meridional : parallel to the A-V axis of the egg

 Horizontal or equatorial : perpendicular to A-V axis.
 Radial : the first two cleavage divison are vertical & perpendicular
to each other & subsequent divisions alternate horizontal & vertical.
 Rotational : 1st cleavage is vertical & 2nd one cell cleaves vertically &
the other horizontally.
 Spiral : first two division are vertical, third horizontal at an oblique
angle.
 Bilateral : 1st cleavage vertical & further division on each side are
mirror image/center on this axis.
 HOLOBLASTIK ?
 MEROBLASTIK ?
RADIAL CLEAVAGE
Spiral cleavage
The aster determine the planes of cleavage
CLEAVAGE & FORMATION of BLASTULA
(Sea urchin)
 Oligolechital-isolechital (little yolk, evenly distributed)
 Holoblastic (blastomere completely separated)
 first two division are meridional (from animal pole to vegetal pole). Perpendicular to
each other.
 3rd is equatorial, producing an eight-cell embryo with blastomeres of almost equal size.
 4th cleavage, however, results in the three distinct types of blastomeres. The four
blastomeres of animal pole undergo a meridional cleavage, resulting 8 cells called
mesomere. The four vegetal blastomeres divide asymmetrically (equatorial), forming
of four large macromere & four small micromere. (3 tiers)
 5th cleavage, mesomere divide equatorially to produce 16 cells (AN1 & AN2),
macromere divide meridionally to produce 8 cells (VG1 & VG2), same as
micromere( but asymmetrically). (4 tiers)
 6th cleavage, all cells divide meridionally to produce a 64 cells. (5 tiers)
 7st , all cells divide meridionally to produce a 128 cell.
 Epithelial monolayer (early blastula) enclosing a central (blastocoel).
(Sea urchin)
(synapta digitata = sea cucumber)
Cleavage with radial symmetry (blastomeres

have equal size) & Holoblastic
 The first two cleavage are meridionally
 3th is equatorially.
 The next cleavage, meridionally &
equatorially, so on until produce a 128 cells.
 blastula
(synapta digitata = sea cucumber)
(crepidula fornicata = mollusc)
 Spiral cleavage mitotic apparatus is oriented at an oblique
angle to long axis of the cell.
 Holoblastic (blastomere completely separated)
 first two division are meridional producing an 4 cell
embryo with blastomeres of equal size.
 3th cleavage, leads to formation of the first quartet of
micromere at the animal pole. (8 cell)
 4th cleavage, 4 micromere divide (12 cell)
 The 5th (16 cell) & 6th (20 cell)
 The 7th (25 cell) , cell at D quadrant is formed precociously.
 1st – 3th shows spiral cleavage pattern
(crepidula fornicata = mollusc)
(amphibia)
 The 1st cleavage begins at animal pole (meridional).

 The 2nd cleavage begins at animal pole with its plane
perpendicular to the 1st cleveage.
 The 3rd cleavage is equatorially, near to animal pole,
dividing into 4 smaller at AP & 4 larger at VP.
 Successive cleavage divisions follow one another rapidly
& synchronously.
 In amphibian, 16 – 64 cell called morula
 After morula stage, blastocoel appears in Animal Pole
above the mass yolk (128 cell).
(amphibia)
(mammals)
 Cleavage in mammal are slow & asynchronous divison.
 Rotational cleavage (first cleavage vertical & 2nd one
cell cleaves vertically & the other horizontally).
 At 8-cell stage, during compaction the blastomere
flatten & tighly joined.
 At 16-cell called morula stage, formed blastocyst
cavity.
 Blastocyst consist of two trophoblast (cells in the outer
wall of blastocyst & inner cell mass (inner surface of
trophoblast .
(mammals)
TERIMA GAJI
Test
1. Apa yang dimaksud dengan : cleavage, blastula, blastomer dan blastosol!
2. Apa yang dimaksud dengan pembelahan : vertikal/meridional,
horizontal/ekuatorial, rotasional, radial dan bilateral!
3. Apa yang dimaksud dengan : meroblastik dan holoblastik!
4. Jelaskan urutan cleavage dan pembentukan blastula pada sea urchin!
5. Jelaskan urutan cleavage dan pembentukan blastula pada synapta
digitata !
6. Jelaskan urutan cleavage dan pembentukan blastula pada crepidula
fornicata!
7. Jelaskan urutan cleavage dan pembentukan blastula pada amfibi!
8. Jelaskan urutan cleavage dan pembentukan blastula pada mamalia!
9. Jelaskan pengertian dari karyokinesis dan sitokinesis!
10. Sebutkan faktor –fakor yang mempengaruhi pola pembelahan!

Cleavage & Blasulasi

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CLEAVAGE & FORMATION OF THE BLASTULA

 Vertical or meridional : parallel to the A-V axis of the egg

Cleavage with radial symmetry (blastomeres

 The 1st cleavage begins at animal pole (meridional).

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