377:. 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.
404:, 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.
426:
382:
421:, 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.
413:, 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
395:, 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.
662:
373:. 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
385:
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
677:
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
271:
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;
261:
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
678:
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.
498:, 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
240:
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
308:
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
262:
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.
101:
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.
767:
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
1641:
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".
1508:
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".
1895:
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".
177:. 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.
693:
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
460:
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
480:
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".
443:
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
228:
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
506:
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
232:—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.
47:
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
391:
Specification of the D macromere and is an important aspect of spiralian development. Although the primary axis, animal-vegetal, is determined during
245:
cells (cells with a small, even distribution of yolk) or in mesolecithal cells or microlecithal cells (moderate concentration of yolk in a gradient)—
1302:
Firmin J, Ecker N, Rivet Danon D, Özgüç Ö, Barraud Lange V, Turlier H, et al. (16 May 2024). "Mechanics of human embryo compaction".
321:
distribution of yolk (sparsely and evenly distributed). Because the cells have only a small concentration of yolk, they require immediate
748:. The morula is now watertight, to contain the fluid that the cells will later pump into the embryo to transform it into the blastocyst.
1753:"Outcomes of preimplantation genetic diagnosis using either zona drilling with acidified Tyrode's solution or partial zona dissection"
417:
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
685:
at the eight-cell stage, having undergone three cleavages the embryo starts to change shape as it develops into a morula and then a
1817:
1694:
1563:
1435:
1359:
1286:
1261:
1236:
936:
905:
876:
839:
110:
The rapid cell cycles are facilitated by maintaining high levels of proteins that control cell cycle progression such as the
717:
that provides distinct characteristics and functions to their cell-cell and cell-medium interfaces. As surface cells become
1946:
180:
The end of cleavage coincides with the beginning of zygotic transcription. This point in non-mammals is referred to as the
361:. Most spiralians undergo equal spiral cleavage, although some undergo unequal cleavage (see below). This group includes
800:
1712:"Preimplantation genetic diagnosis and chromosome analysis of blastomeres using comparative genomic hybridization"
772:. Initially dispersed in hundreds of water pockets throughout the embryo, the fluid collects into a single large
2263:
216:. Each blastomere produced by early embryonic cleavage does not have the capacity to develop into a complete
2231:
2176:
1955:
733:
are developed with the other blastomeres. With further compaction the individual outer blastomeres, the
682:
127:
1924:
1128:"Evolutionary implications of the mode of D quadrant specification in coelomates with spiral cleavage"
792:. The trophoblasts will eventually give rise to the embryonic contribution to the placenta called the
322:
78:(partial cleavage). The pole of the egg with the highest concentration of yolk is referred to as the
1453:"Polarity-Dependent Distribution of Angiomotin Localizes Hippo Signaling in Preimplantation Embryos"
2236:
2148:
2033:
1939:
788:
on one side of the cavity that will go on to produce the embryo proper. The embryo is now termed a
2000:
1881:
773:
655:
115:
272:
compared with bilateral meroblastic cleavage, in which the blastomeres stay partially connected.
2221:
2120:
334:
2226:
2216:
2060:
1425:
856:
756:
1581:"Mechanics of mouse blastocyst hatching revealed by a hydrogel-based microdeformation assay"
1840:
1651:
1592:
1464:
1311:
970:
864:
769:
414:
146:
1451:
Hirate Y, Hirahara S, Inoue Ki, Suzuki A, Alarcon VB, Akimoto K, et al. (July 2013).
8:
1970:
1932:
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1596:
1468:
1315:
974:
868:
1777:
1752:
1615:
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1401:
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1975:
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1636:
1634:
1620:
1579:
Leonavicius K, Royer C, Preece C, Davies B, Biggins JS, Srinivas S (9 October 2018).
1559:
1536:
1531:
1490:
1431:
1406:
1355:
1327:
1282:
1257:
1232:
1209:
1047:
1026:"Conserved mechanism of dorsoventral axis determination in equal-cleaving spiralians"
1006:
1001:
958:
932:
901:
872:
835:
294:, in which the spindle axes are parallel or at right angles to the polar axis of the
161:
and the centrosomes are organized by centrioles brought into the egg by the sperm as
1153:
2138:
2101:
2082:
1904:
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1083:
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996:
978:
777:
577:
166:
1631:
799:
A single cell can be removed from a pre-compaction eight-cell embryo and used for
2015:
1522:
781:
741:
142:
1204:
1187:
2194:
2092:
1886:
1833:
Proceedings of the
National Academy of Sciences of the United States of America
1768:
1751:
Kim HJ, Kim CH, Lee SM, Choe SA, Lee JY, Jee BC, et al. (September 2012).
1392:
1323:
963:
Proceedings of the
National Academy of Sciences of the United States of America
893:
745:
738:
730:
666:
665:
First stages of cleavage in a fertilized mammalian egg. Semidiagrammatic. z.p.
517:
503:
354:
340:
206:
28:
1476:
827:
2257:
2143:
2087:
1882:"What are the 'advantages' of developing a deuterostome pattern of embryonic"
1689:(11th ed.). Philadelphia: Lippincott William & Wilkins. p. 45.
722:
714:
425:
213:
174:
90:
36:
1853:
1728:
1711:
1663:
1605:
959:"Evolution of the bilaterian body plan: what have we learned from annelids?"
381:
2158:
2113:
2108:
1916:
1786:
1737:
1671:
1640:
1624:
1540:
1494:
1410:
1354:(Fifth ed.). Philadelphia, PA: Churchill Livingstone. pp. 35–36.
1331:
1213:
1088:
1071:
1051:
1042:
1025:
1010:
983:
726:
673:
a. Two-cell stage b. Four-cell stage c. Eight-cell stage d, e. Morula stage
670:
544:
477:
283:
229:
162:
141:
work together to result in cleavage. The mitotic apparatus is made up of a
134:
94:
79:
32:
1872:
2153:
2078:
2020:
1558:(Forty-first ed.). Philadelphia, PA: Elsevier Limited. p. 165.
1231:(Eleventh ed.). Sunderland, Massachusetts: Sinauer Associates, Inc.
807:
737:, become indistinguishable as they become organised into a thin sheet of
734:
611:
495:
418:
318:
242:
181:
154:
138:
83:
1954:
2209:
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2010:
2005:
1990:
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789:
764:
718:
690:
686:
622:
540:
291:
287:
202:
158:
60:
48:
44:
20:
992:
2042:
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on the trophoblasts pump sodium into the morula, drawing in water by
697:. Once the embryo has divided into 16 cells, it begins to resemble a
626:
597:
585:
548:
499:
461:
392:
370:
98:
1375:
Gauster M, Moser G, Wernitznig S, Kupper N, Huppertz B (June 2022).
2186:
2168:
2130:
2047:
1072:"Evolutionary Modifications of the Spiralian Developmental Program"
710:
698:
581:
570:
563:
358:
331:
185:
119:
56:
1377:"Early human trophoblast development: from morphology to function"
1829:"Cleavage patterns and the topology of the metazoan tree of life"
1507:
793:
760:
559:
555:
491:
469:
431:
366:
362:
150:
2204:
1995:
1980:
752:
638:
386:
mitotic spindle, or through the formation of a polar lobe (PL).
374:
314:
295:
217:
210:
111:
52:
40:
201:
Determinate cleavage (also called mosaic cleavage) is in most
702:
170:
1578:
1374:
1301:
618:
473:
465:
123:
67:
1424:
Larsen WJ (2001). Sherman LS, Potter SS, Scott WJ (eds.).
894:"Early Development of the Nematode Caenorhabditis elegans"
755:
after three or four days, and begins to take in fluid, as
1556:
Gray's anatomy: the anatomical basis of clinical practice
1450:
353:
Spiral cleavage is conserved between many members of the
1188:"The MAPK cascade in equally cleaving spiralian embryos"
661:
1430:(3rd ed.). Elsevier Health Sciences. p. 20.
1279:
Vertebrates: Comparative
Anatomy, Function, Evolution
606:
A. Telolecithal (dense yolk throughout most of cell)
592:
B. Mesolecithal (moderate vegetal yolk disposition)
325:
into the uterine wall in order to receive nutrients.
1805:
828:"An Introduction to Early Developmental Processes"
1897:Differentiation; Research in Biological Diversity
1894:
776:, called blastocoel, following a process akin to
535:A. Isolecithal (sparse, evenly distributed yolk)
343:, undergoes holoblastic rotational cell cleavage.
2255:
1125:
1757:Clinical and Experimental Reproductive Medicine
1585:Proceedings of the National Academy of Sciences
956:
1281:(4th ed.). McGraw-Hill. pp. 158–64.
1226:
205:. It results in the developmental fate of the
1940:
1750:
854:
713:). Concomitantly, they develop an inside-out
654:"Morula" redirects here. For other uses, see
516:Summary of the main patterns of cleavage and
429:Spiral cleavage in marine snail of the genus
93:in that it increases the number of cells and
1185:
952:
950:
948:
861:Biological physics of the developing embryo
1947:
1933:
1349:
1069:
863:. Cambridge University Press. p. 27.
633:B. Centrolecithal (yolk in center of egg)
513:
55:. Cleavage ends with the formation of the
1862:
1852:
1826:
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1727:
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1111:
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1087:
1041:
1000:
982:
282:Radial cleavage is characteristic of the
82:while the opposite is referred to as the
66:Depending mostly on the concentration of
1803:
1017:
945:
763:from the maternal environment to become
660:
424:
380:
1368:
1276:
1251:
1220:
1065:
1063:
1061:
931:(11th ed.). Sinauer. p. 268.
926:
891:
825:
2256:
1709:
1703:
1684:
1678:
1423:
1338:
1256:(7th ed.). Sinauer. p. 214.
1160:
1104:
806:Differences exist between cleavage in
780:. Embryoblast cells also known as the
529:II. Meroblastic (incomplete) cleavage
1928:
1879:
1186:Lambert JD, Nagy LM (November 2003).
1023:
957:Shankland M, Seaver EC (April 2000).
744:. They are still enclosed within the
89:Cleavage differs from other forms of
16:Division of cells in the early embryo
1744:
1381:Cellular and Molecular Life Sciences
1058:
834:(6th ed.). Sinauer Associates.
784:form a compact mass of cells at the
317:display rotational cleavage, and an
191:
184:and appears to be controlled by the
1808:Principles of Developmental Biology
1076:Integrative and Comparative Biology
526:I. Holoblastic (complete) cleavage
51:and form a compact mass called the
13:
1796:
1145:10.1046/j.1420-9101.1992.5020205.x
14:
2275:
857:"Cleavage and blastula formation"
751:In humans, the morula enters the
165:. Cytokinesis is mediated by the
1909:10.1111/j.1432-0436.2006.00114.x
1126:Freeman G, Lundelius JW (1992).
223:
70:in the egg, the cleavage can be
1572:
1501:
1444:
1417:
1295:
1270:
1245:
1227:Gilbert SF, Barresi MJ (2016).
1132:Journal of Evolutionary Biology
803:, and the embryo will recover.
130:) promotes entry into mitosis.
920:
885:
848:
819:
689:. At the eight-cell stage the
438:
235:
196:
157:. The asters are nucleated by
74:(total or entire cleavage) or
43:of many species undergo rapid
1:
855:Forgács G, Newman SA (2005).
813:
302:
1687:Langman's medical embryology
1523:10.1016/j.devcel.2017.01.006
617:2. Discoidal cleavage (some
265:
105:
97:mass without increasing the
7:
2232:Splanchnopleuric mesenchyme
2177:Splanchnopleuric mesenchyme
1956:Human embryonic development
1880:Onken M (4 February 1999).
1205:10.1016/j.ydbio.2003.07.006
1070:Boyer BC, Henry JQ (1998).
683:human embryonic development
637:Superficial cleavage (most
596:Displaced radial cleavage (
128:maturation promoting factor
10:
2280:
1827:Valentine JW (July 1997).
1769:10.5653/cerm.2012.39.3.118
1393:10.1007/s00018-022-04377-0
1324:10.1038/s41586-024-07351-x
653:
649:
532:
339:, a popular developmental
2185:
2167:
2129:
2069:
2056:
2029:
1963:
1716:Human Reproduction Update
1532:21.11116/0000-0002-8C77-B
1477:10.1016/j.cub.2013.05.014
1352:Larsen's human embryology
701:, hence the name morula (
490:In superficial cleavage,
347:
276:
186:nuclear-cytoplasmic ratio
33:development of the embryo
2237:Somatopleuric mesenchyme
2149:Somatopleuric mesenchyme
1958:in the first three weeks
721:, they begin to tightly
576:4. Rotational cleavage (
116:cyclin-dependent kinases
1854:10.1073/pnas.94.15.8001
1804:Wilt F, Hake S (2004).
1664:10.1126/science.aaw7709
1606:10.1073/pnas.1719930115
1024:Henry J (August 2002).
656:Morula (disambiguation)
610:1. Bilateral cleavage (
569:3. Bilateral cleavage (
209:being set early in the
169:made up of polymers of
149:made up of polymers of
2121:Regional specification
1350:Schoenwolf GC (2015).
1043:10.1006/dbio.2002.0741
984:10.1073/pnas.97.9.4434
757:sodium-potassium pumps
674:
435:
387:
182:midblastula transition
2264:Developmental biology
2227:Intraembryonic coelom
1729:10.1093/humupd/dmh050
1254:Developmental biology
1229:Developmental Biology
1192:Developmental Biology
1030:Developmental Biology
929:Developmental biology
898:Developmental Biology
832:Developmental Biology
664:
428:
384:
357:taxa, referred to as
286:, which include some
114:and their associated
1554:Standring S (2016).
1089:10.1093/icb/38.4.621
770:hydraulic fracturing
554:2. Spiral cleavage (
539:1. Radial cleavage (
118:(CDKs). The complex
1845:1997PNAS...94.8001V
1656:2019Sci...365..465D
1597:2018PNAS..11510375L
1591:(41): 10375–10380.
1469:2013CBio...23.1181H
1316:2024Natur.629..646F
1277:Kardong KV (2006).
1252:Gilbert SF (2003).
975:2000PNAS...97.4434S
927:Gilbert SF (2016).
892:Gilbert SF (2000).
869:2005bpde.book.....F
826:Gilbert SF (2000).
810:and other mammals.
612:cephalopod molluscs
522:
126:also known as MPF (
27:is the division of
1685:Sadler TW (2010).
1511:Developmental Cell
675:
514:
436:
388:
2251:
2250:
2247:
2246:
1976:Oocyte activation
1839:(15): 8001–8005.
1819:978-0-393-97430-0
1710:Wilton L (2005).
1696:978-0-7817-9069-7
1650:(6452): 465–468.
1565:978-0-7020-5230-9
1517:(3): 235–247.e7.
1463:(13): 1181–1194.
1437:978-0-443-06583-5
1361:978-1-4557-0684-6
1310:(8012): 646–651.
1288:978-0-07-060750-7
1263:978-0-87893-258-0
1238:978-1-60535-470-5
938:978-1-60535-470-5
907:978-0-87893-243-6
878:978-0-521-78337-8
841:978-0-87893-243-6
808:placental mammals
801:genetic screening
647:
646:
578:placental mammals
518:yolk accumulation
257:holoblastic, and
192:Types of cleavage
133:The processes of
2271:
2139:Surface ectoderm
2102:Primitive groove
2083:Primitive streak
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2066:
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1427:Human embryology
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969:(9): 4434–4437.
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924:
918:
917:
915:
914:
900:(6th ed.).
889:
883:
882:
852:
846:
845:
823:
778:Ostwald ripening
742:epithelial cells
729:are formed, and
523:
411:unequal cleavage
167:contractile ring
2279:
2278:
2274:
2273:
2272:
2270:
2269:
2268:
2254:
2253:
2252:
2243:
2181:
2163:
2125:
2058:
2052:
2031:
2025:
2016:Inner cell mass
1959:
1953:
1923:
1820:
1812:. W.W. Norton.
1799:
1797:Further reading
1794:
1749:
1745:
1708:
1704:
1697:
1683:
1679:
1639:
1632:
1577:
1573:
1566:
1552:
1548:
1506:
1502:
1457:Current Biology
1449:
1445:
1438:
1422:
1418:
1373:
1369:
1362:
1348:
1339:
1300:
1296:
1289:
1275:
1271:
1264:
1250:
1246:
1239:
1225:
1221:
1184:
1161:
1124:
1105:
1068:
1059:
1022:
1018:
955:
946:
939:
925:
921:
912:
910:
908:
890:
886:
879:
853:
849:
842:
824:
820:
816:
782:inner cell mass
739:tightly adhered
731:tight junctions
659:
652:
494:occurs but not
441:
355:lophotrochozoan
350:
305:
279:
268:
238:
226:
199:
194:
173:protein called
153:protein called
143:central spindle
108:
17:
12:
11:
5:
2277:
2267:
2266:
2249:
2248:
2245:
2244:
2242:
2241:
2240:
2239:
2234:
2229:
2219:
2214:
2213:
2212:
2207:
2197:
2195:Axial mesoderm
2191:
2189:
2183:
2182:
2180:
2179:
2173:
2171:
2165:
2164:
2162:
2161:
2156:
2151:
2146:
2141:
2135:
2133:
2127:
2126:
2124:
2123:
2118:
2117:
2116:
2106:
2105:
2104:
2099:
2093:Primitive node
2090:
2075:
2073:
2064:
2054:
2053:
2051:
2050:
2045:
2039:
2037:
2027:
2026:
2024:
2023:
2018:
2013:
2008:
2003:
1998:
1993:
1988:
1983:
1978:
1973:
1967:
1965:
1961:
1960:
1952:
1951:
1944:
1937:
1929:
1922:
1921:
1892:
1887:MadSci Network
1877:
1824:
1818:
1800:
1798:
1795:
1793:
1792:
1763:(3): 118–124.
1743:
1702:
1695:
1677:
1630:
1571:
1564:
1546:
1500:
1443:
1436:
1416:
1367:
1360:
1337:
1294:
1287:
1269:
1262:
1244:
1237:
1219:
1198:(2): 231–241.
1159:
1103:
1057:
1036:(2): 343–355.
1016:
944:
937:
919:
906:
884:
877:
847:
840:
817:
815:
812:
786:embryonic pole
746:zona pellucida
667:Zona pellucida
651:
648:
645:
644:
643:
642:
631:
630:
615:
603:
602:
601:
590:
589:
574:
567:
552:
531:
530:
527:
520:(after and ).
512:
511:
504:centrolecithal
487:
486:
482:
481:
457:
456:
440:
437:
423:
422:
406:
405:
402:equal cleavage
397:
396:
379:
378:
349:
346:
345:
344:
341:model organism
327:
326:
311:
310:
304:
301:
300:
299:
278:
275:
274:
273:
267:
264:
237:
234:
225:
222:
198:
195:
193:
190:
175:microfilaments
137:(mitosis) and
107:
104:
15:
9:
6:
4:
3:
2:
2276:
2265:
2262:
2261:
2259:
2238:
2235:
2233:
2230:
2228:
2225:
2224:
2223:
2222:Lateral plate
2220:
2218:
2215:
2211:
2208:
2206:
2203:
2202:
2201:
2198:
2196:
2193:
2192:
2190:
2188:
2184:
2178:
2175:
2174:
2172:
2170:
2166:
2160:
2157:
2155:
2152:
2150:
2147:
2145:
2144:Neuroectoderm
2142:
2140:
2137:
2136:
2134:
2132:
2128:
2122:
2119:
2115:
2112:
2111:
2110:
2107:
2103:
2100:
2098:
2094:
2091:
2089:
2088:Primitive pit
2086:
2085:
2084:
2080:
2077:
2076:
2074:
2072:
2068:
2065:
2062:
2055:
2049:
2046:
2044:
2041:
2040:
2038:
2035:
2028:
2022:
2019:
2017:
2014:
2012:
2009:
2007:
2004:
2002:
1999:
1997:
1994:
1992:
1989:
1987:
1984:
1982:
1979:
1977:
1974:
1972:
1971:Fertilization
1969:
1968:
1966:
1962:
1957:
1950:
1945:
1943:
1938:
1936:
1931:
1930:
1927:
1918:
1914:
1910:
1906:
1902:
1898:
1893:
1889:
1888:
1883:
1878:
1874:
1870:
1865:
1860:
1855:
1850:
1846:
1842:
1838:
1834:
1830:
1825:
1821:
1815:
1810:
1809:
1802:
1801:
1788:
1784:
1779:
1774:
1770:
1766:
1762:
1758:
1754:
1747:
1739:
1735:
1730:
1725:
1721:
1717:
1713:
1706:
1698:
1692:
1688:
1681:
1673:
1669:
1665:
1661:
1657:
1653:
1649:
1645:
1637:
1635:
1626:
1622:
1617:
1612:
1607:
1602:
1598:
1594:
1590:
1586:
1582:
1575:
1567:
1561:
1557:
1550:
1542:
1538:
1533:
1528:
1524:
1520:
1516:
1512:
1504:
1496:
1492:
1487:
1482:
1478:
1474:
1470:
1466:
1462:
1458:
1454:
1447:
1439:
1433:
1429:
1428:
1420:
1412:
1408:
1403:
1398:
1394:
1390:
1386:
1382:
1378:
1371:
1363:
1357:
1353:
1346:
1344:
1342:
1333:
1329:
1325:
1321:
1317:
1313:
1309:
1305:
1298:
1290:
1284:
1280:
1273:
1265:
1259:
1255:
1248:
1240:
1234:
1230:
1223:
1215:
1211:
1206:
1201:
1197:
1193:
1189:
1182:
1180:
1178:
1176:
1174:
1172:
1170:
1168:
1166:
1164:
1155:
1151:
1146:
1141:
1138:(2): 205–47.
1137:
1133:
1129:
1122:
1120:
1118:
1116:
1114:
1112:
1110:
1108:
1099:
1095:
1090:
1085:
1082:(4): 621–33.
1081:
1077:
1073:
1066:
1064:
1062:
1053:
1049:
1044:
1039:
1035:
1031:
1027:
1020:
1012:
1008:
1003:
998:
994:
990:
985:
980:
976:
972:
968:
964:
960:
953:
951:
949:
940:
934:
930:
923:
909:
903:
899:
895:
888:
880:
874:
870:
866:
862:
858:
851:
843:
837:
833:
829:
822:
818:
811:
809:
804:
802:
797:
795:
791:
787:
783:
779:
775:
771:
766:
762:
758:
754:
749:
747:
743:
740:
736:
732:
728:
727:gap junctions
724:
720:
716:
712:
708:
704:
700:
696:
692:
688:
684:
679:
672:
668:
663:
657:
640:
636:
635:
634:
628:
624:
620:
616:
613:
609:
608:
607:
604:
600:, some fish )
599:
595:
594:
593:
587:
583:
579:
575:
572:
568:
565:
561:
557:
553:
550:
546:
545:hemichordates
542:
538:
537:
536:
533:
528:
525:
524:
521:
519:
509:
505:
501:
497:
493:
489:
488:
484:
483:
479:
475:
471:
467:
463:
459:
458:
454:
453:
452:
450:
446:
434:
433:
427:
420:
416:
412:
408:
407:
403:
399:
398:
394:
390:
389:
383:
376:
372:
368:
364:
360:
356:
352:
351:
342:
338:
337:
333:
329:
328:
324:
320:
316:
313:
312:
309:equatorially.
307:
306:
297:
293:
289:
285:
284:deuterostomes
281:
280:
270:
269:
263:
260:
256:
253:holoblastic,
252:
249:holoblastic,
248:
244:
233:
231:
230:deuterostomes
224:Indeterminate
221:
219:
215:
212:
208:
204:
189:
188:(about 1:6).
187:
183:
178:
176:
172:
168:
164:
160:
156:
152:
148:
144:
140:
136:
131:
129:
125:
121:
117:
113:
103:
100:
96:
92:
91:cell division
87:
85:
81:
77:
73:
69:
64:
62:
58:
54:
50:
46:
42:
38:
37:fertilization
34:
31:in the early
30:
26:
22:
2217:Intermediate
2159:Neural crest
2114:Gastrulation
1985:
1903:(1): 84–92.
1900:
1896:
1885:
1836:
1832:
1807:
1760:
1756:
1746:
1722:(1): 33–41.
1719:
1715:
1705:
1686:
1680:
1647:
1643:
1588:
1584:
1574:
1555:
1549:
1514:
1510:
1503:
1460:
1456:
1446:
1426:
1419:
1384:
1380:
1370:
1351:
1307:
1303:
1297:
1278:
1272:
1253:
1247:
1228:
1222:
1195:
1191:
1135:
1131:
1079:
1075:
1033:
1029:
1019:
966:
962:
928:
922:
911:. Retrieved
897:
887:
860:
850:
831:
821:
805:
798:
785:
765:blastocoelic
750:
735:trophoblasts
706:
694:
680:
676:
671:Polar bodies
632:
605:
591:
534:
515:
507:
478:telolecithal
448:
444:
442:
430:
410:
401:
335:
323:implantation
258:
254:
250:
246:
239:
227:
200:
179:
163:basal bodies
155:microtubules
135:karyokinesis
132:
109:
88:
80:vegetal pole
75:
71:
65:
63:in mammals.
59:, or of the
35:, following
24:
18:
2154:Neurulation
2079:Archenteron
2071:Germ layers
2021:Trophoblast
691:blastomeres
541:echinoderms
496:cytokinesis
485:Superficial
449:superficial
439:Meroblastic
419:cytokinesis
319:isolecithal
292:echinoderms
288:vertebrates
243:isolecithal
236:Holoblastic
214:development
203:protostomes
197:Determinate
159:centrosomes
139:cytokinesis
99:cytoplasmic
84:animal pole
76:meroblastic
72:holoblastic
49:blastomeres
45:cell cycles
2210:Somitomere
2097:Blastopore
2061:Trilaminar
2011:Blastocyst
2006:Blastocoel
2001:Cavitation
1991:Blastomere
1387:(6): 345.
913:2007-09-17
814:References
790:blastocyst
719:epithelial
687:blastocyst
627:monotremes
623:sauropsids
598:amphibians
586:marsupials
508:Drosophila
502:that have
500:arthropods
476:that have
462:monotremes
336:C. elegans
303:Rotational
255:rotational
145:and polar
61:blastocyst
21:embryology
2043:Hypoblast
2034:Bilaminar
582:nematodes
571:tunicates
564:flatworms
549:amphioxus
455:Discoidal
445:discoidal
393:oogenesis
371:sipuncula
266:Bilateral
247:bilateral
106:Mechanism
2258:Category
2200:Paraxial
2187:Mesoderm
2169:Endoderm
2131:Ectoderm
2109:Gastrula
2048:Epiblast
1986:Cleavage
1917:17244024
1787:23106043
1738:15569702
1672:31371608
1625:30232257
1541:28171747
1495:23791731
1411:35661923
1332:38693259
1214:14597198
1154:85304565
1052:12167409
1011:10781038
715:polarity
711:mulberry
699:mulberry
669:. p.gl.
560:mollusks
556:annelids
470:reptiles
367:molluscs
363:annelids
359:Spiralia
332:nematode
120:cyclin B
57:blastula
25:cleavage
2057:Week 3
2030:Week 2
1873:9223303
1841:Bibcode
1778:3479235
1652:Bibcode
1644:Science
1616:6187134
1593:Bibcode
1486:3742369
1465:Bibcode
1402:9167809
1312:Bibcode
1098:4620189
971:Bibcode
865:Bibcode
794:chorion
761:osmosis
650:Mammals
639:insects
558:, most
492:mitosis
432:Trochus
315:Mammals
151:tubulin
112:cyclins
95:nuclear
41:zygotes
2205:Somite
1996:Morula
1981:Zygote
1964:Week 1
1915:
1871:
1861:
1816:
1785:
1775:
1736:
1693:
1670:
1623:
1613:
1562:
1539:
1493:
1483:
1434:
1409:
1399:
1358:
1330:
1304:Nature
1285:
1260:
1235:
1212:
1152:
1096:
1050:
1009:
999:
993:122407
991:
935:
904:
875:
838:
774:cavity
753:uterus
723:adhere
695:morula
472:, and
375:zygote
369:, and
348:Spiral
296:oocyte
277:Radial
259:spiral
251:radial
218:embryo
211:embryo
147:asters
53:morula
39:. The
1864:21545
1150:S2CID
1094:JSTOR
1002:34316
989:JSTOR
707:morus
703:Latin
466:birds
415:aster
207:cells
171:actin
29:cells
1913:PMID
1869:PMID
1814:ISBN
1783:PMID
1734:PMID
1691:ISBN
1668:PMID
1621:PMID
1560:ISBN
1537:PMID
1491:PMID
1432:ISBN
1407:PMID
1356:ISBN
1328:PMID
1283:ISBN
1258:ISBN
1233:ISBN
1210:PMID
1048:PMID
1007:PMID
933:ISBN
902:ISBN
873:ISBN
836:ISBN
619:fish
474:fish
447:and
330:The
290:and
124:CDK1
68:yolk
1905:doi
1859:PMC
1849:doi
1773:PMC
1765:doi
1724:doi
1660:doi
1648:365
1611:PMC
1601:doi
1589:115
1527:hdl
1519:doi
1481:PMC
1473:doi
1397:PMC
1389:doi
1320:doi
1308:629
1200:doi
1196:263
1140:doi
1084:doi
1038:doi
1034:248
997:PMC
979:doi
796:.
725:as
681:In
409:In
400:In
19:In
2260::
1911:.
1901:75
1899:.
1884:.
1867:.
1857:.
1847:.
1837:94
1835:.
1831:.
1781:.
1771:.
1761:39
1759:.
1755:.
1732:.
1720:11
1718:.
1714:.
1666:.
1658:.
1646:.
1633:^
1619:.
1609:.
1599:.
1587:.
1583:.
1535:.
1525:.
1515:40
1513:.
1489:.
1479:.
1471:.
1461:23
1459:.
1455:.
1405:.
1395:.
1385:79
1383:.
1379:.
1340:^
1326:.
1318:.
1306:.
1208:.
1194:.
1190:.
1162:^
1148:.
1134:.
1130:.
1106:^
1092:.
1080:38
1078:.
1074:.
1060:^
1046:.
1032:.
1028:.
1005:.
995:.
987:.
977:.
967:97
965:.
961:.
947:^
896:.
871:.
859:.
830:.
709::
705:,
625:,
621:,
584:,
580:,
562:,
547:,
543:,
468:,
464:,
451:.
365:,
220:.
86:.
23:,
2095:/
2081:/
2063:)
2059:(
2036:)
2032:(
1948:e
1941:t
1934:v
1919:.
1907::
1890:.
1875:.
1851::
1843::
1822:.
1789:.
1767::
1740:.
1726::
1699:.
1674:.
1662::
1654::
1627:.
1603::
1595::
1568:.
1543:.
1529::
1521::
1497:.
1475::
1467::
1440:.
1413:.
1391::
1364:.
1334:.
1322::
1314::
1291:.
1266:.
1241:.
1216:.
1202::
1156:.
1142::
1136:5
1100:.
1086::
1054:.
1040::
1013:.
981::
973::
941:.
916:.
881:.
867::
844:.
658:.
641:)
629:)
614:)
588:)
573:)
566:)
551:)
510:.
298:.
122:/
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.