Embryology is the study of the development of an organism, commencing with the union of male and female gametes. Embryology literally means the study of embryos, but this definition is restrictive. An embryo is an immature organism contained within the coverings of an egg or within the body of the mother. Strictly speaking, the embryonic period ends at metamorphosis, hatching, or birth. Since developmental processes continue beyond these events, the scope of embryology is customarily broadened to encompass the entire life history of an organism. Embryology may, in this wider context, consider the mechanisms of both asexual reproduction and regeneration.

After the 1950s, with the DNA helical structure being discovered by James D. Watson and Francis Crick, (in collaboration with Rosalind Franklin and Maurice Wilkins) and the increasing knowledge in the field of molecular biology, developmental biology emerged as the field of study that correlates the genes and such morphological changes; in other words, which genes are responsible for each morphological change that takes place in an embryo, and how these genes are regulated.

Neuroembryology

Neuroembryology refers to the development of an embryos nervous system. At the middle of the third week the neural plate appears which originates from the ectoderm.

See also

• Ontogeny
• Embryogenesis
• Recapitulation theory

 References

• UNSW Embryology Large resource of information and media

Further reading

• Scott F. Gilbert. Developmental Biology. Sinauer, 2003. ISBN 0-87893-258-5.
• Lewis Wolpert. Principles of Development. Oxford University Press, 2006. ISBN 0-19-927536-X.

Mammalian development of embryo and development and fetus (some dates are approximate - see Carnegie stages)
Week 1: Zygote | Morula | Blastula/Blastomere/Blastosphere | Archenteron/Primitive streak | Blastopore | Allantois | Trophoblast (Cytotrophoblast | Syncytiotrophoblast | Gestational sac) Week 2: Yolk sac | Vitelline duct | Bilaminar disc Week 3: Hensen's node | Gastrula/Gastrulation | Trilaminar embryo Branchial arch (1st) | Branchial pouch | Meckel's cartilage | Somite/Somitomere | Germ layer (Ectoderm, Endoderm, Mesoderm, Chordamesoderm, Paraxial mesoderm, Intermediate mesoderm, Lateral plate mesoderm)
Histogenesis and Organogenesis
Circulatory system: Primitive atrium | Primitive ventricle | Bulbus cordis | Truncus arteriosus | Ostium primum | Foramen ovale | Ductus venosus | Ductus arteriosus | Aortic arches | Septum primum | Septum secundum | Cardinal veins Nervous system: Neural development/Neurulation | Neurula | Neural folds | Neural groove | Neural tube | Neural crest | Neuromere (Rhombomere) | Notochord | Optic vesicles | Optic stalk | Optic cup Digestive system: Foregut | Midgut | Hindgut | Proctodeum | Rathke's pouch | Septum transversum Urinary/Reproductive system: Urogenital folds | Urethral groove | Urogenital sinus | Kidney development (Pronephros | Mesonephros | Ureteric bud | Metanephric blastema) | Fetal genital development (Wolffian duct | Müllerian duct | Gubernaculum | Labioscrotal folds) Glands: Thyroglossal duct Uterine support: Placenta | Umbilical cord (Umbilical artery, Umbilical vein, Wharton's jelly) | Amniotic sac (Amnion, Chorion) Limb development: Limb bud | Apical Ectodermal Ridge/AER