388:. At the 4-cell stage, the A and C macromeres meet at the animal pole, creating the animal cross-furrow, while the B and D macromeres meet at the vegetal pole, creating the vegetal cross-furrow. With each successive cleavage cycle, the macromeres give rise to quartets of smaller micromeres at the animal pole. The divisions that produce these quartets occur at an oblique angle, an angle that is not a multiple of 90 degrees, to the animal-vegetal axis. Each quartet of micromeres is rotated relative to their parent macromere, and the chirality of this rotation differs between odd- and even-numbered quartets, meaning that there is alternating symmetry between the odd and even quartets. In other words, the orientation of divisions that produces each quartet alternates between being clockwise and counterclockwise with respect to the animal pole. The alternating cleavage pattern that occurs as the quartets are generated produces quartets of micromeres that reside in the cleavage furrows of the four macromeres. When viewed from the animal pole, this arrangement of cells displays a spiral pattern.
415:, the first two cell divisions produce four macromeres that are indistinguishable from one another. Each macromere has the potential of becoming the D macromere. After the formation of the third quartet, one of the macromeres initiates maximum contact with the overlying micromeres in the animal pole of the embryo. This contact is required to distinguish one macromere as the official D quadrant blastomere. In equally cleaving spiral embryos, the D quadrant is not specified until after the formation of the third quartet, when contact with the micromeres dictates one cell to become the future D blastomere. Once specified, the D blastomere signals to surrounding micromeres to lay out their cell fates.
432:, in which both macromeres inherit part of the animal region of the egg, but only the bigger macromere inherits the vegetal region. The second mechanism of unequal cleavage involves the production of an enucleate, membrane bound, cytoplasmic protrusion, called a polar lobe. This polar lobe forms at the vegetal pole during cleavage, and then gets shunted to the D blastomere. The polar lobe contains vegetal cytoplasm, which becomes inherited by the future D macromere.
437:
393:
424:, the first two cell divisions are unequal producing four cells in which one cell is bigger than the other three. This larger cell is specified as the D macromere. Unlike equally cleaving spiralians, the D macromere is specified at the four-cell stage during unequal cleavage. Unequal cleavage can occur in two ways. One method involves asymmetric positioning of the cleavage spindle. This occurs when the
406:, the secondary axis, dorsal-ventral, is determined by the specification of the D quadrant. The D macromere facilitates cell divisions that differ from those produced by the other three macromeres. Cells of the D quadrant give rise to dorsal and posterior structures of the spiralian. Two known mechanisms exist to specify the D quadrant. These mechanisms include equal cleavage and unequal cleavage.
673:
384:. Spiral cleavage can vary between species, but generally the first two cell divisions result in four macromeres, also called blastomeres, (A, B, C, D) each representing one quadrant of the embryo. These first two cleavages are not oriented in planes that occur at right angles parallel to the animal-vegetal axis of the
396:
D quadrant specification through equal and unequal cleavage mechanisms. At the 4-cell stage of equal cleavage, the D macromere has not been specified yet. It will be specified after the formation of the third quartet of micromeres. Unequal cleavage occurs in two ways: asymmetric positioning of the
688:
Compared to other fast developing animals, mammals have a slower rate of division that is between 12 and 24 hours. Initially synchronous, these cellular divisions progressively become more and more asynchronous. Zygotic transcription starts at the two-, four-, or eight-cell stage depending on the
282:
The first cleavage results in bisection of the zygote into left and right halves. The following cleavage planes are centered on this axis and result in the two halves being mirror images of one another. In bilateral holoblastic cleavage, the divisions of the blastomeres are complete and separate;
272:
holoblastic, cleavage. These holoblastic cleavage planes pass all the way through isolecithal zygotes during the process of cytokinesis. Coeloblastula is the next stage of development for eggs that undergo these radial cleavages. In holoblastic eggs, the first cleavage always occurs along the
689:
species (for example, mouse zygotic transcription begins towards the end of the zygote stage and becomes significant at the two-cell stage, whereas human embryos begin zygotic transcription at the eight-cell stage). Cleavage is holoblastic and rotational.
509:, resulting in a polynuclear cell. With the yolk positioned in the center of the egg cell, the nuclei migrate to the periphery of the egg, and the plasma membrane grows inward, partitioning the nuclei into individual cells. Superficial cleavage occurs in
251:
In holoblastic cleavage, the zygote and blastomeres are completely divided during the cleavage, so the number of blastomeres doubles with each cleavage. In the absence of a large concentration of yolk, four major cleavage types can be observed in
319:
Rotational cleavage involves a normal first division along the meridional axis, giving rise to two daughter cells. The way in which this cleavage differs is that one of the daughter cells divides meridionally, whilst the other divides
273:
vegetal-animal axis of the egg, the second cleavage is perpendicular to the first. From here, the spatial arrangement of blastomeres can follow various patterns, due to different planes of cleavage, in various organisms.
112:
mass. This means that with each successive subdivision, there is roughly half the cytoplasm in each daughter cell than before that division, and thus the ratio of nuclear to cytoplasmic material increases.
778:
fluid. As a consequence to increased osmotic pressure, the accumulation of fluid raises the hydrostatic pressure inside the embryo. Hydrostatic pressure breaks open cell-cell contacts within the embryo by
1652:
Dumortier JG, Le Verge-Serandour M, Tortorelli AF, Mielke A, de Plater L, Turlier H, et al. (2 August 2019). "Hydraulic fracturing and active coarsening position the lumen of the mouse blastocyst".
1519:
Korotkevich E, Niwayama R, Courtois A, Friese S, Berger N, Buchholz F, et al. (February 2017). "The Apical Domain Is
Required and Sufficient for the First Lineage Segregation in the Mouse Embryo".
1906:
Lee SC, Mietchen D, Cho JH, Kim YS, Kim C, Hong KS, et al. (January 2007). "In vivo magnetic resonance microscopy of differentiation in
Xenopus laevis embryos from the first cleavage onwards".
188:. Karyokinesis and cytokinesis are independent but spatially and temporally coordinated processes. While mitosis can occur in the absence of cytokinesis, cytokinesis requires the mitotic apparatus.
704:
are initially round, and only loosely adhered. With further division in the process of compaction the cells flatten onto one another. At the 16–cell stage the compacted embryo is called a
471:
In discoidal cleavage, the cleavage furrows do not penetrate the yolk. The embryo forms a disc of cells, called a blasto-disc, on top of the yolk. Discoidal cleavage is commonly found in
491:
egg cells (egg cells with the yolk concentrated at one end). The layer of cells that have incompletely divided and are in contact with the yolk are called the "syncytial layer".
454:
In the presence of a large concentration of yolk in the fertilized egg cell, the cell can undergo partial, or meroblastic, cleavage. Two major types of meroblastic cleavage are
239:
A cell can only be indeterminate (also called regulative) if it has a complete set of undisturbed animal/vegetal cytoarchitectural features. It is characteristic of
517:
egg cells (egg cells with the yolk located in the center of the cell). This type of cleavage can work to promote synchronicity in developmental timing, such as in
243:—when the original cell in a deuterostome embryo divides, the two resulting cells can be separated, and each one can individually develop into a whole organism.
58:
with no significant overall growth, producing a cluster of cells the same size as the original zygote. The different cells derived from cleavage are called
402:
Specification of the D macromere and is an important aspect of spiralian development. Although the primary axis, animal-vegetal, is determined during
256:
cells (cells with a small, even distribution of yolk) or in mesolecithal cells or microlecithal cells (moderate concentration of yolk in a gradient)—
1828:
1705:
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850:
1957:
1313:
Firmin J, Ecker N, Rivet Danon D, Özgüç Ö, Barraud Lange V, Turlier H, et al. (16 May 2024). "Mechanics of human embryo compaction".
332:
distribution of yolk (sparsely and evenly distributed). Because the cells have only a small concentration of yolk, they require immediate
759:. The morula is now watertight, to contain the fluid that the cells will later pump into the embryo to transform it into the blastocyst.
1764:"Outcomes of preimplantation genetic diagnosis using either zona drilling with acidified Tyrode's solution or partial zona dissection"
428:
at one pole attaches to the cell membrane, causing it to be much smaller than the aster at the other pole. This results in an unequal
811:
696:
at the eight-cell stage, having undergone three cleavages the embryo starts to change shape as it develops into a morula and then a
2274:
121:
The rapid cell cycles are facilitated by maintaining high levels of proteins that control cell cycle progression such as the
728:
that provides distinct characteristics and functions to their cell-cell and cell-medium interfaces. As surface cells become
191:
The end of cleavage coincides with the beginning of zygotic transcription. This point in non-mammals is referred to as the
372:. Most spiralians undergo equal spiral cleavage, although some undergo unequal cleavage (see below). This group includes
2242:
2187:
1966:
693:
138:
1723:"Preimplantation genetic diagnosis and chromosome analysis of blastomeres using comparative genomic hybridization"
783:. Initially dispersed in hundreds of water pockets throughout the embryo, the fluid collects into a single large
333:
2247:
2159:
2044:
1950:
227:. Each blastomere produced by early embryonic cleavage does not have the capacity to develop into a complete
2011:
784:
666:
126:
2232:
2131:
345:
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are developed with the other blastomeres. With further compaction the individual outer blastomeres, the
2237:
2227:
2071:
767:
1935:
1139:"Evolutionary implications of the mode of D quadrant specification in coelomates with spiral cleavage"
803:. The trophoblasts will eventually give rise to the embryonic contribution to the placenta called the
1851:
1662:
1603:
1475:
1322:
981:
875:
780:
425:
157:
89:(partial cleavage). The pole of the egg with the highest concentration of yolk is referred to as the
1464:"Polarity-Dependent Distribution of Angiomotin Localizes Hippo Signaling in Preimplantation Embryos"
1981:
1943:
799:
on one side of the cavity that will go on to produce the embryo proper. The embryo is now termed a
1892:
1160:
1104:
999:
283:
compared with bilateral meroblastic cleavage, in which the blastomeres stay partially connected.
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1986:
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1592:"Mechanics of mouse blastocyst hatching revealed by a hydrogel-based microdeformation assay"
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1462:
Hirate Y, Hirahara S, Inoue Ki, Suzuki A, Alarcon VB, Akimoto K, et al. (July 2013).
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1590:
Leonavicius K, Royer C, Preece C, Davies B, Biggins JS, Srinivas S (9 October 2018).
1542:
1037:"Conserved mechanism of dorsoventral axis determination in equal-cleaving spiralians"
1012:
969:
733:
725:
305:, in which the spindle axes are parallel or at right angles to the polar axis of the
224:
185:
172:
and the centrosomes are organized by centrioles brought into the egg by the sperm as
101:
47:
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2119:
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681:
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173:
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105:
90:
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A single cell can be removed from a pre-compaction eight-cell embryo and used for
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149:
94:
1844:
Proceedings of the
National Academy of Sciences of the United States of America
1779:
1762:
Kim HJ, Kim CH, Lee SM, Choe SA, Lee JY, Jee BC, et al. (September 2012).
1403:
1334:
974:
Proceedings of the
National Academy of Sciences of the United States of America
904:
676:
First stages of cleavage in a fertilized mammalian egg. Semidiagrammatic. z.p.
17:
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2107:
2081:
2021:
2016:
2001:
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838:
800:
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551:
302:
298:
213:
169:
71:
59:
55:
31:
1893:"What are the 'advantages' of developing a deuterostome pattern of embryonic"
1700:(11th ed.). Philadelphia: Lippincott William & Wilkins. p. 45.
2053:
1864:
1739:
1722:
1674:
1616:
970:"Evolution of the bilaterian body plan: what have we learned from annelids?"
637:
608:
596:
559:
510:
472:
403:
381:
109:
1927:
1797:
1748:
1682:
1635:
1551:
1505:
1421:
1365:(Fifth ed.). Philadelphia, PA: Churchill Livingstone. pp. 35–36.
1342:
1224:
1099:
1082:
1062:
1053:
1036:
1021:
994:
684:
a. Two-cell stage b. Four-cell stage c. Eight-cell stage d, e. Morula stage
152:
work together to result in cleavage. The mitotic apparatus is made up of a
1883:
2197:
2179:
2141:
2058:
1569:(Forty-first ed.). Philadelphia, PA: Elsevier Limited. p. 165.
1242:(Eleventh ed.). Sunderland, Massachusetts: Sinauer Associates, Inc.
748:, become indistinguishable as they become organised into a thin sheet of
721:
709:
592:
581:
574:
369:
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196:
130:
67:
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161:
1003:
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2006:
1991:
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on the trophoblasts pump sodium into the morula, drawing in water by
763:
708:. Once the embryo has divided into 16 cells, it begins to resemble a
649:
385:
325:
306:
228:
221:
122:
63:
51:
43:
1386:
Gauster M, Moser G, Wernitznig S, Kupper N, Huppertz B (June 2022).
524:
1083:"Evolutionary Modifications of the Spiralian Developmental Program"
1388:"Early human trophoblast development: from morphology to function"
713:
671:
435:
391:
181:
1840:"Cleavage patterns and the topology of the metazoan tree of life"
672:
629:
484:
476:
134:
78:
1939:
397:
mitotic spindle, or through the formation of a polar lobe (PL).
212:
Determinate cleavage (also called mosaic cleavage) is in most
1435:
Larsen WJ (2001). Sherman LS, Potter SS, Scott WJ (eds.).
905:"Early Development of the Nematode Caenorhabditis elegans"
766:
after three or four days, and begins to take in fluid, as
1567:
Gray's anatomy: the anatomical basis of clinical practice
364:
Spiral cleavage is conserved between many members of the
1199:"The MAPK cascade in equally cleaving spiralian embryos"
1441:(3rd ed.). Elsevier Health Sciences. p. 20.
1290:
Vertebrates: Comparative
Anatomy, Function, Evolution
617:
A. Telolecithal (dense yolk throughout most of cell)
603:
B. Mesolecithal (moderate vegetal yolk disposition)
336:
into the uterine wall in order to receive nutrients.
2196:
2178:
2140:
2080:
2067:
2040:
1974:
1816:
839:"An Introduction to Early Developmental Processes"
1908:Differentiation; Research in Biological Diversity
787:, called blastocoel, following a process akin to
546:A. Isolecithal (sparse, evenly distributed yolk)
354:, undergoes holoblastic rotational cell cleavage.
1768:Clinical and Experimental Reproductive Medicine
1596:Proceedings of the National Academy of Sciences
1292:(4th ed.). McGraw-Hill. pp. 158–64.
216:. It results in the developmental fate of the
1951:
724:). Concomitantly, they develop an inside-out
665:"Morula" redirects here. For other uses, see
527:Summary of the main patterns of cleavage and
440:Spiral cleavage in marine snail of the genus
104:in that it increases the number of cells and
8:
963:
961:
959:
872:Biological physics of the developing embryo
2077:
1958:
1944:
1936:
874:. Cambridge University Press. p. 27.
644:B. Centrolecithal (yolk in center of egg)
66:. Cleavage ends with the formation of the
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293:Radial cleavage is characteristic of the
93:while the opposite is referred to as the
77:Depending mostly on the concentration of
774:from the maternal environment to become
1076:
1074:
1072:
942:(11th ed.). Sinauer. p. 268.
829:
1267:(7th ed.). Sinauer. p. 214.
817:Differences exist between cleavage in
791:. Embryoblast cells also known as the
540:II. Meroblastic (incomplete) cleavage
1197:Lambert JD, Nagy LM (November 2003).
968:Shankland M, Seaver EC (April 2000).
755:. They are still enclosed within the
100:Cleavage differs from other forms of
27:Division of cells in the early embryo
7:
1392:Cellular and Molecular Life Sciences
845:(6th ed.). Sinauer Associates.
795:form a compact mass of cells at the
328:display rotational cleavage, and an
195:and appears to be controlled by the
1819:Principles of Developmental Biology
1087:Integrative and Comparative Biology
537:I. Holoblastic (complete) cleavage
62:and form a compact mass called the
1156:10.1046/j.1420-9101.1992.5020205.x
25:
868:"Cleavage and blastula formation"
762:In humans, the morula enters the
176:. Cytokinesis is mediated by the
1920:10.1111/j.1432-0436.2006.00114.x
1137:Freeman G, Lundelius JW (1992).
81:in the egg, the cleavage can be
1238:Gilbert SF, Barresi MJ (2016).
1143:Journal of Evolutionary Biology
814:, and the embryo will recover.
141:) promotes entry into mitosis.
700:. At the eight-cell stage the
168:. The asters are nucleated by
85:(total or entire cleavage) or
54:of many species undergo rapid
1:
866:Forgács G, Newman SA (2005).
1698:Langman's medical embryology
1534:10.1016/j.devcel.2017.01.006
628:2. Discoidal cleavage (some
108:mass without increasing the
2243:Splanchnopleuric mesenchyme
2188:Splanchnopleuric mesenchyme
1967:Human embryonic development
1891:Onken M (4 February 1999).
1216:10.1016/j.ydbio.2003.07.006
1081:Boyer BC, Henry JQ (1998).
694:human embryonic development
648:Superficial cleavage (most
607:Displaced radial cleavage (
139:maturation promoting factor
2291:
1838:Valentine JW (July 1997).
1780:10.5653/cerm.2012.39.3.118
1404:10.1007/s00018-022-04377-0
1335:10.1038/s41586-024-07351-x
664:
543:
350:, a popular developmental
1727:Human Reproduction Update
1543:21.11116/0000-0002-8C77-B
1488:10.1016/j.cub.2013.05.014
1363:Larsen's human embryology
712:, hence the name morula (
501:In superficial cleavage,
197:nuclear-cytoplasmic ratio
44:development of the embryo
2248:Somatopleuric mesenchyme
2160:Somatopleuric mesenchyme
1969:in the first three weeks
732:, they begin to tightly
587:4. Rotational cleavage (
127:cyclin-dependent kinases
1865:10.1073/pnas.94.15.8001
1815:Wilt F, Hake S (2004).
1675:10.1126/science.aaw7709
1617:10.1073/pnas.1719930115
1035:Henry J (August 2002).
667:Morula (disambiguation)
621:1. Bilateral cleavage (
580:3. Bilateral cleavage (
220:being set early in the
180:made up of polymers of
160:made up of polymers of
2132:Regional specification
1361:Schoenwolf GC (2015).
1054:10.1006/dbio.2002.0741
995:10.1073/pnas.97.9.4434
768:sodium-potassium pumps
685:
446:
398:
193:midblastula transition
2275:Developmental biology
2238:Intraembryonic coelom
1740:10.1093/humupd/dmh050
1265:Developmental biology
1240:Developmental Biology
1203:Developmental Biology
1041:Developmental Biology
940:Developmental biology
909:Developmental Biology
843:Developmental Biology
675:
439:
395:
368:taxa, referred to as
297:, which include some
125:and their associated
1565:Standring S (2016).
1100:10.1093/icb/38.4.621
781:hydraulic fracturing
565:2. Spiral cleavage (
550:1. Radial cleavage (
129:(CDKs). The complex
1856:1997PNAS...94.8001V
1667:2019Sci...365..465D
1608:2018PNAS..11510375L
1602:(41): 10375–10380.
1480:2013CBio...23.1181H
1327:2024Natur.629..646F
1288:Kardong KV (2006).
1263:Gilbert SF (2003).
986:2000PNAS...97.4434S
938:Gilbert SF (2016).
903:Gilbert SF (2000).
880:2005bpde.book.....F
837:Gilbert SF (2000).
821:and other mammals.
623:cephalopod molluscs
533:
137:also known as MPF (
38:is the division of
1696:Sadler TW (2010).
1522:Developmental Cell
686:
525:
447:
399:
2262:
2261:
2258:
2257:
1987:Oocyte activation
1850:(15): 8001–8005.
1830:978-0-393-97430-0
1721:Wilton L (2005).
1707:978-0-7817-9069-7
1661:(6452): 465–468.
1576:978-0-7020-5230-9
1528:(3): 235–247.e7.
1474:(13): 1181–1194.
1448:978-0-443-06583-5
1372:978-1-4557-0684-6
1321:(8012): 646–651.
1299:978-0-07-060750-7
1274:978-0-87893-258-0
1249:978-1-60535-470-5
949:978-1-60535-470-5
918:978-0-87893-243-6
889:978-0-521-78337-8
852:978-0-87893-243-6
819:placental mammals
812:genetic screening
658:
657:
589:placental mammals
529:yolk accumulation
268:holoblastic, and
203:Types of cleavage
144:The processes of
16:(Redirected from
2282:
2150:Surface ectoderm
2113:Primitive groove
2094:Primitive streak
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1438:Human embryology
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980:(9): 4434–4437.
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926:
925:
911:(6th ed.).
900:
894:
893:
863:
857:
856:
834:
789:Ostwald ripening
753:epithelial cells
740:are formed, and
534:
422:unequal cleavage
178:contractile ring
21:
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2027:Inner cell mass
1970:
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1823:. W.W. Norton.
1814:
1810:
1808:Further reading
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1708:
1695:
1694:
1690:
1651:
1650:
1643:
1589:
1588:
1584:
1577:
1564:
1563:
1559:
1518:
1517:
1513:
1468:Current Biology
1461:
1460:
1456:
1449:
1434:
1433:
1429:
1385:
1384:
1380:
1373:
1360:
1359:
1350:
1312:
1311:
1307:
1300:
1287:
1286:
1282:
1275:
1262:
1261:
1257:
1250:
1237:
1236:
1232:
1196:
1195:
1172:
1136:
1135:
1116:
1080:
1079:
1070:
1034:
1033:
1029:
967:
966:
957:
950:
937:
936:
932:
923:
921:
919:
902:
901:
897:
890:
865:
864:
860:
853:
836:
835:
831:
827:
793:inner cell mass
750:tightly adhered
742:tight junctions
670:
663:
505:occurs but not
452:
366:lophotrochozoan
361:
316:
290:
279:
249:
237:
210:
205:
184:protein called
164:protein called
154:central spindle
119:
28:
23:
22:
18:Spiral cleavage
15:
12:
11:
5:
2288:
2286:
2278:
2277:
2267:
2266:
2260:
2259:
2256:
2255:
2253:
2252:
2251:
2250:
2245:
2240:
2230:
2225:
2224:
2223:
2218:
2208:
2206:Axial mesoderm
2202:
2200:
2194:
2193:
2191:
2190:
2184:
2182:
2176:
2175:
2173:
2172:
2167:
2162:
2157:
2152:
2146:
2144:
2138:
2137:
2135:
2134:
2129:
2128:
2127:
2117:
2116:
2115:
2110:
2104:Primitive node
2101:
2086:
2084:
2075:
2065:
2064:
2062:
2061:
2056:
2050:
2048:
2038:
2037:
2035:
2034:
2029:
2024:
2019:
2014:
2009:
2004:
1999:
1994:
1989:
1984:
1978:
1976:
1972:
1971:
1965:
1963:
1962:
1955:
1948:
1940:
1933:
1932:
1903:
1898:MadSci Network
1888:
1835:
1829:
1811:
1809:
1806:
1804:
1803:
1774:(3): 118–124.
1754:
1713:
1706:
1688:
1641:
1582:
1575:
1557:
1511:
1454:
1447:
1427:
1378:
1371:
1348:
1305:
1298:
1280:
1273:
1255:
1248:
1230:
1209:(2): 231–241.
1170:
1114:
1068:
1047:(2): 343–355.
1027:
955:
948:
930:
917:
895:
888:
858:
851:
828:
826:
823:
797:embryonic pole
757:zona pellucida
678:Zona pellucida
662:
659:
656:
655:
654:
653:
642:
641:
626:
614:
613:
612:
601:
600:
585:
578:
563:
542:
541:
538:
531:(after and ).
523:
522:
515:centrolecithal
498:
497:
493:
492:
468:
467:
451:
448:
434:
433:
417:
416:
413:equal cleavage
408:
407:
390:
389:
360:
357:
356:
355:
352:model organism
338:
337:
322:
321:
315:
312:
311:
310:
289:
286:
285:
284:
278:
275:
248:
245:
236:
233:
209:
206:
204:
201:
186:microfilaments
148:(mitosis) and
118:
115:
26:
24:
14:
13:
10:
9:
6:
4:
3:
2:
2287:
2276:
2273:
2272:
2270:
2249:
2246:
2244:
2241:
2239:
2236:
2235:
2234:
2233:Lateral plate
2231:
2229:
2226:
2222:
2219:
2217:
2214:
2213:
2212:
2209:
2207:
2204:
2203:
2201:
2199:
2195:
2189:
2186:
2185:
2183:
2181:
2177:
2171:
2168:
2166:
2163:
2161:
2158:
2156:
2155:Neuroectoderm
2153:
2151:
2148:
2147:
2145:
2143:
2139:
2133:
2130:
2126:
2123:
2122:
2121:
2118:
2114:
2111:
2109:
2105:
2102:
2100:
2099:Primitive pit
2097:
2096:
2095:
2091:
2088:
2087:
2085:
2083:
2079:
2076:
2073:
2066:
2060:
2057:
2055:
2052:
2051:
2049:
2046:
2039:
2033:
2030:
2028:
2025:
2023:
2020:
2018:
2015:
2013:
2010:
2008:
2005:
2003:
2000:
1998:
1995:
1993:
1990:
1988:
1985:
1983:
1982:Fertilization
1980:
1979:
1977:
1973:
1968:
1961:
1956:
1954:
1949:
1947:
1942:
1941:
1938:
1929:
1925:
1921:
1917:
1913:
1909:
1904:
1900:
1899:
1894:
1889:
1885:
1881:
1876:
1871:
1866:
1861:
1857:
1853:
1849:
1845:
1841:
1836:
1832:
1826:
1821:
1820:
1813:
1812:
1807:
1799:
1795:
1790:
1785:
1781:
1777:
1773:
1769:
1765:
1758:
1755:
1750:
1746:
1741:
1736:
1732:
1728:
1724:
1717:
1714:
1709:
1703:
1699:
1692:
1689:
1684:
1680:
1676:
1672:
1668:
1664:
1660:
1656:
1648:
1646:
1642:
1637:
1633:
1628:
1623:
1618:
1613:
1609:
1605:
1601:
1597:
1593:
1586:
1583:
1578:
1572:
1568:
1561:
1558:
1553:
1549:
1544:
1539:
1535:
1531:
1527:
1523:
1515:
1512:
1507:
1503:
1498:
1493:
1489:
1485:
1481:
1477:
1473:
1469:
1465:
1458:
1455:
1450:
1444:
1440:
1439:
1431:
1428:
1423:
1419:
1414:
1409:
1405:
1401:
1397:
1393:
1389:
1382:
1379:
1374:
1368:
1364:
1357:
1355:
1353:
1349:
1344:
1340:
1336:
1332:
1328:
1324:
1320:
1316:
1309:
1306:
1301:
1295:
1291:
1284:
1281:
1276:
1270:
1266:
1259:
1256:
1251:
1245:
1241:
1234:
1231:
1226:
1222:
1217:
1212:
1208:
1204:
1200:
1193:
1191:
1189:
1187:
1185:
1183:
1181:
1179:
1177:
1175:
1171:
1166:
1162:
1157:
1152:
1149:(2): 205–47.
1148:
1144:
1140:
1133:
1131:
1129:
1127:
1125:
1123:
1121:
1119:
1115:
1110:
1106:
1101:
1096:
1093:(4): 621–33.
1092:
1088:
1084:
1077:
1075:
1073:
1069:
1064:
1060:
1055:
1050:
1046:
1042:
1038:
1031:
1028:
1023:
1019:
1014:
1009:
1005:
1001:
996:
991:
987:
983:
979:
975:
971:
964:
962:
960:
956:
951:
945:
941:
934:
931:
920:
914:
910:
906:
899:
896:
891:
885:
881:
877:
873:
869:
862:
859:
854:
848:
844:
840:
833:
830:
824:
822:
820:
815:
813:
808:
806:
802:
798:
794:
790:
786:
782:
777:
773:
769:
765:
760:
758:
754:
751:
747:
743:
739:
738:gap junctions
735:
731:
727:
723:
719:
715:
711:
707:
703:
699:
695:
690:
683:
679:
674:
668:
660:
651:
647:
646:
645:
639:
635:
631:
627:
624:
620:
619:
618:
615:
611:, some fish )
610:
606:
605:
604:
598:
594:
590:
586:
583:
579:
576:
572:
568:
564:
561:
557:
556:hemichordates
553:
549:
548:
547:
544:
539:
536:
535:
532:
530:
520:
516:
512:
508:
504:
500:
499:
495:
494:
490:
486:
482:
478:
474:
470:
469:
465:
464:
463:
461:
457:
449:
445:
444:
438:
431:
427:
423:
419:
418:
414:
410:
409:
405:
401:
400:
394:
387:
383:
379:
375:
371:
367:
363:
362:
358:
353:
349:
348:
344:
340:
339:
335:
331:
327:
324:
323:
320:equatorially.
318:
317:
313:
308:
304:
300:
296:
295:deuterostomes
292:
291:
287:
281:
280:
276:
274:
271:
267:
264:holoblastic,
263:
260:holoblastic,
259:
255:
246:
244:
242:
241:deuterostomes
235:Indeterminate
234:
232:
230:
226:
223:
219:
215:
207:
202:
200:
199:(about 1:6).
198:
194:
189:
187:
183:
179:
175:
171:
167:
163:
159:
155:
151:
147:
142:
140:
136:
132:
128:
124:
116:
114:
111:
107:
103:
102:cell division
98:
96:
92:
88:
84:
80:
75:
73:
69:
65:
61:
57:
53:
49:
48:fertilization
45:
42:in the early
41:
37:
33:
19:
2228:Intermediate
2170:Neural crest
2125:Gastrulation
1996:
1914:(1): 84–92.
1911:
1907:
1896:
1847:
1843:
1818:
1771:
1767:
1757:
1733:(1): 33–41.
1730:
1726:
1716:
1697:
1691:
1658:
1654:
1599:
1595:
1585:
1566:
1560:
1525:
1521:
1514:
1471:
1467:
1457:
1437:
1430:
1395:
1391:
1381:
1362:
1318:
1314:
1308:
1289:
1283:
1264:
1258:
1239:
1233:
1206:
1202:
1146:
1142:
1090:
1086:
1044:
1040:
1030:
977:
973:
939:
933:
922:. Retrieved
908:
898:
871:
861:
842:
832:
816:
809:
796:
776:blastocoelic
761:
746:trophoblasts
717:
705:
691:
687:
682:Polar bodies
643:
616:
602:
545:
526:
518:
489:telolecithal
459:
455:
453:
441:
421:
412:
346:
334:implantation
269:
265:
261:
257:
250:
238:
211:
190:
174:basal bodies
166:microtubules
146:karyokinesis
143:
120:
99:
91:vegetal pole
86:
82:
76:
74:in mammals.
70:, or of the
46:, following
35:
29:
2165:Neurulation
2090:Archenteron
2082:Germ layers
2032:Trophoblast
702:blastomeres
552:echinoderms
507:cytokinesis
496:Superficial
460:superficial
450:Meroblastic
430:cytokinesis
330:isolecithal
303:echinoderms
299:vertebrates
254:isolecithal
247:Holoblastic
225:development
214:protostomes
208:Determinate
170:centrosomes
150:cytokinesis
110:cytoplasmic
95:animal pole
87:meroblastic
83:holoblastic
60:blastomeres
56:cell cycles
2221:Somitomere
2108:Blastopore
2072:Trilaminar
2022:Blastocyst
2017:Blastocoel
2012:Cavitation
2002:Blastomere
1398:(6): 345.
924:2007-09-17
825:References
801:blastocyst
730:epithelial
698:blastocyst
638:monotremes
634:sauropsids
609:amphibians
597:marsupials
519:Drosophila
513:that have
511:arthropods
487:that have
473:monotremes
347:C. elegans
314:Rotational
266:rotational
156:and polar
72:blastocyst
32:embryology
2054:Hypoblast
2045:Bilaminar
593:nematodes
582:tunicates
575:flatworms
560:amphioxus
466:Discoidal
456:discoidal
404:oogenesis
382:sipuncula
277:Bilateral
258:bilateral
117:Mechanism
2269:Category
2211:Paraxial
2198:Mesoderm
2180:Endoderm
2142:Ectoderm
2120:Gastrula
2059:Epiblast
1997:Cleavage
1928:17244024
1798:23106043
1749:15569702
1683:31371608
1636:30232257
1552:28171747
1506:23791731
1422:35661923
1343:38693259
1225:14597198
1165:85304565
1063:12167409
1022:10781038
726:polarity
722:mulberry
710:mulberry
680:. p.gl.
571:mollusks
567:annelids
481:reptiles
378:molluscs
374:annelids
370:Spiralia
343:nematode
131:cyclin B
68:blastula
36:cleavage
2068:Week 3
2041:Week 2
1884:9223303
1852:Bibcode
1789:3479235
1663:Bibcode
1655:Science
1627:6187134
1604:Bibcode
1497:3742369
1476:Bibcode
1413:9167809
1323:Bibcode
1109:4620189
982:Bibcode
876:Bibcode
805:chorion
772:osmosis
661:Mammals
650:insects
569:, most
503:mitosis
443:Trochus
326:Mammals
162:tubulin
123:cyclins
106:nuclear
52:zygotes
2216:Somite
2007:Morula
1992:Zygote
1975:Week 1
1926:
1882:
1872:
1827:
1796:
1786:
1747:
1704:
1681:
1634:
1624:
1573:
1550:
1504:
1494:
1445:
1420:
1410:
1369:
1341:
1315:Nature
1296:
1271:
1246:
1223:
1163:
1107:
1061:
1020:
1010:
1004:122407
1002:
946:
915:
886:
849:
785:cavity
764:uterus
734:adhere
706:morula
483:, and
386:zygote
380:, and
359:Spiral
307:oocyte
288:Radial
270:spiral
262:radial
229:embryo
222:embryo
158:asters
64:morula
50:. The
1875:21545
1161:S2CID
1105:JSTOR
1013:34316
1000:JSTOR
718:morus
714:Latin
477:birds
426:aster
218:cells
182:actin
40:cells
1924:PMID
1880:PMID
1825:ISBN
1794:PMID
1745:PMID
1702:ISBN
1679:PMID
1632:PMID
1571:ISBN
1548:PMID
1502:PMID
1443:ISBN
1418:PMID
1367:ISBN
1339:PMID
1294:ISBN
1269:ISBN
1244:ISBN
1221:PMID
1059:PMID
1018:PMID
944:ISBN
913:ISBN
884:ISBN
847:ISBN
630:fish
485:fish
458:and
341:The
301:and
135:CDK1
79:yolk
1916:doi
1870:PMC
1860:doi
1784:PMC
1776:doi
1735:doi
1671:doi
1659:365
1622:PMC
1612:doi
1600:115
1538:hdl
1530:doi
1492:PMC
1484:doi
1408:PMC
1400:doi
1331:doi
1319:629
1211:doi
1207:263
1151:doi
1095:doi
1049:doi
1045:248
1008:PMC
990:doi
807:.
736:as
692:In
420:In
411:In
30:In
2271::
1922:.
1912:75
1910:.
1895:.
1878:.
1868:.
1858:.
1848:94
1846:.
1842:.
1792:.
1782:.
1772:39
1770:.
1766:.
1743:.
1731:11
1729:.
1725:.
1677:.
1669:.
1657:.
1644:^
1630:.
1620:.
1610:.
1598:.
1594:.
1546:.
1536:.
1526:40
1524:.
1500:.
1490:.
1482:.
1472:23
1470:.
1466:.
1416:.
1406:.
1396:79
1394:.
1390:.
1351:^
1337:.
1329:.
1317:.
1219:.
1205:.
1201:.
1173:^
1159:.
1145:.
1141:.
1117:^
1103:.
1091:38
1089:.
1085:.
1071:^
1057:.
1043:.
1039:.
1016:.
1006:.
998:.
988:.
978:97
976:.
972:.
958:^
907:.
882:.
870:.
841:.
720::
716:,
636:,
632:,
595:,
591:,
573:,
558:,
554:,
479:,
475:,
462:.
376:,
231:.
97:.
34:,
2106:/
2092:/
2074:)
2070:(
2047:)
2043:(
1959:e
1952:t
1945:v
1930:.
1918::
1901:.
1886:.
1862::
1854::
1833:.
1800:.
1778::
1751:.
1737::
1710:.
1685:.
1673::
1665::
1638:.
1614::
1606::
1579:.
1554:.
1540::
1532::
1508:.
1486::
1478::
1451:.
1424:.
1402::
1375:.
1345:.
1333::
1325::
1302:.
1277:.
1252:.
1227:.
1213::
1167:.
1153::
1147:5
1111:.
1097::
1065:.
1051::
1024:.
992::
984::
952:.
927:.
892:.
878::
855:.
669:.
652:)
640:)
625:)
599:)
584:)
577:)
562:)
521:.
309:.
133:/
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.