Illustration of a human embryo at six weeks gestational age
9-week human fetus from ectopic pregnancy
Anatomical terminology
[edit on Wikidata]
Limb development in vertebrates is an area of active research in both developmental and evolutionary biology, with much of the latter work focused on the transition from fin to limb.[1]
Limb formation begins in the morphogenetic limb field, as mesenchymal cells from the lateral plate mesoderm proliferate to the point that they cause the ectoderm above to bulge out, forming a limb bud. Fibroblast growth factor (FGF) induces the formation of an organizer at the end of the limb bud, called the apical ectodermal ridge (AER), which guides further development and controls cell death. Programmed cell death is necessary to eliminate webbing between digits.
The limb field is a region specified by expression of certain Hox genes, a subset of homeotic genes, and T-box transcription factors – Tbx5 for forelimb or wing development, and Tbx4 for leg or hindlimb development. Establishment of the forelimb field (but not hindlimb field) requires retinoic acid signaling in the developing trunk of the embryo from which the limb buds emerge.[2][3] Also, although excess retinoic acid can alter limb patterning by ectopically activating Shh or Meis1/Meis2 expression, genetic studies in mouse that eliminate retinoic acid synthesis have shown that RA is not required for limb patterning.[4]
The limb bud remains active throughout much of limb development as it stimulates the creation and positive feedback retention of two signaling regions: the AER and its subsequent creation of the zone of polarizing activity (ZPA) with the mesenchymal cells.[5] In addition to the dorsal-ventral axis created by the ectodermal expression of competitive Wnt7a and BMP signals respectively, these AER and ZPA signaling centers are crucial to the proper formation of a limb that is correctly oriented with its corresponding axial polarity in the developing organism.[6][7] Because these signaling systems reciprocally sustain each other's activity, limb development is essentially autonomous after these signaling regions have been established.[5]
^Stewart, TA; Bhat, R; Newman, SA (2017). "The evolutionary origin of digit patterning". EvoDevo. 8: 21. doi:10.1186/s13227-017-0084-8. PMC 5697439. PMID 29201343.
^Stratford T, Horton C, Maden M (1996). "Retinoic acid is required for the initiation of outgrowth in the chick limb bud". Curr Biol. 6 (9): 1124–33. doi:10.1016/S0960-9822(02)70679-9. PMID 8805369. S2CID 14662908.
^Zhao X, Sirbu IO, Mic FA, et al. (June 2009). "Retinoic acid promotes limb induction through effects on body axis extension but is unnecessary for limb patterning". Curr. Biol. 19 (12): 1050–7. doi:10.1016/j.cub.2009.04.059. PMC 2701469. PMID 19464179.
^Cunningham, T.J.; Duester, G. (2015). "Mechanisms of retinoic acid signalling and its roles in organ and limb development". Nat. Rev. Mol. Cell Biol. 16 (2): 110–123. doi:10.1038/nrm3932. PMC 4636111. PMID 25560970.
^ abTickle, C (October 2015). "How the embryo makes a limb: determination, polarity and identity". Journal of Anatomy. 227 (4): 418–30. doi:10.1111/joa.12361. PMC 4580101. PMID 26249743.
^Parr, BA; McMahon, AP (23 March 1995). "Dorsalizing signal Wnt-7a required for normal polarity of D-V and A-P axes of mouse limb". Nature. 374 (6520): 350–3. Bibcode:1995Natur.374..350P. doi:10.1038/374350a0. PMID 7885472. S2CID 4254409.
^Pizette, S; Abate-Shen, C; Niswander, L (November 2001). "BMP controls proximodistal outgrowth, via induction of the apical ectodermal ridge, and dorsoventral patterning in the vertebrate limb". Development. 128 (22): 4463–74. doi:10.1242/dev.128.22.4463. PMID 11714672.
Limbdevelopment in vertebrates is an area of active research in both developmental and evolutionary biology, with much of the latter work focused on the...
patterning of limbdevelopment in mice embryos and that CYP26B1 is significant to prevent apoptosis of those limb tissues to further proper development of mice...
The limb bud is a structure formed early in vertebrate limbdevelopment. As a result of interactions between the ectoderm and underlying mesoderm, formation...
each limb bud and acts as a major signaling center to ensure proper development of a limb. After the limb bud induces AER formation, the AER and limb mesenchyme—including...
maintains the outgrowth of the chick limb bud through interaction with FGF8, an apical ectodermal factor". Development. 124 (11): 2235–2244. doi:10.1242/dev...
evo-devo model for studying the evolution of vertebrate limb diversity. Tetrapod limbdevelopment involves many signaling molecules such as FGF, BMP, SHH...
role in some amphibians and reptiles in their ability to regenerate lost limbs, especially HoxA and HoxD genes. If the processes involved in forming new...
possible causes are an injury to the apical ectodermal ridge during upper limbdevelopment, intrauterine compression, or maternal drug use (thalidomide). Classification...
third week to the tenth week. At the end of the fourth week limbdevelopment begins. Limb buds appear on the ventrolateral aspect of the body. They consist...
embryologic development of snakes from other vertebrates, two significant factors being the elongation of the body and the lack of limbdevelopment. The elongation...
affected. Causes include previous joint injury, abnormal joint or limbdevelopment, and inherited factors. Risk is greater in those who are overweight...
Embryogenesis Endoderm Eye development Gastrulation Germ layer Germ line development Gonadogenesis Heart development Histogenesis Limbdevelopment List of human cell...
powered upper-limb prostheses: State of the art and challenges for clinical use". The Journal of Rehabilitation Research and Development. 48 (6): 643–659...
vascularisation of the limb with further studies being required to confirm or deny a potential role of Eph in limbdevelopment. As a member of the RTK...
2017). "Saunders's framework for understanding limbdevelopment as a platform for investigating limb evolution". Developmental Biology. 429 (2): 401–408...
patterning is often found in combination with other patterns: vertebrate limbdevelopment is one of the many phenotypes exhibiting Turing patterning overlapped...
Fgf8 and Fgf10 are two of the critical players in limbdevelopment. In the forelimb initiation and limb growth in mice, axial (lengthwise) cues from the...
synchronously push off the substrate to propel the animal forwards. Unlike limbdevelopment in tetrapods, where the forelimb and hindlimb buds emerge at roughly...
locus causes allelic imbalance and ectopic expression of Shh during limbdevelopment". Developmental Dynamics. 240 (5): 1163–1172. doi:10.1002/dvdy.22623...
the limb bud develops into bones, tendons, muscles and joints. Limb bud development relies not only on the ZPA, but also many different genes, signals...
Limbic resonance is the idea that the capacity for sharing deep emotional states arises from the limbic system of the brain. These states include the...
early-limbdevelopment stage. Cercarial penetration of host tissue involves proteolytic enzymes. The exact mechanism which alters limbdevelopment is unknown...
flag patterning is often found in combination with others: vertebrate limbdevelopment is one of the many phenotypes exhibiting French flag patterning overlapped...
their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both...
thalamus by the zona limitans intrathalamica. In vertebrates, the development of limbs and digits depends on the secretion of sonic hedgehog by the zone...
vertebrates are limbless, limb-reduced, or apodous, with a body plan consisting of a head and vertebral column, but no adjoining limbs such as legs or fins...
is not derived from blood plasma but is produced by the thick ascending limb of the loop of Henle of the mammalian kidney. While the monomeric molecule...
also known as Horn Kolb syndrome, is a genetic condition that affects limbdevelopment, resulting in shortened arms and legs and absent hands and feet on...
worked with embryology, argued that limb and tissue reformation bore many similarities to embryonic development. Building off of the work of German embryologist...
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