From Encyclopedia Jr, free information reference for Kids
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 helixical 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.
[edit] See also
- Ontogeny
- Embryogenesis
- Recapitulation theory
- Neuroembryology
[edit] References
[edit] Further reading
| Mammalian development of embryo and development and fetus (some dates are approximate - see Carnegie stages) - |
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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)
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| Histogenesis and Organogenesis |
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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)
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