Embryology

Information about Embryology

Embryology is the study of the development of an embryo. An embryo is defined as any vertebrate in a stage before birth or hatching. Embryology refers to the development of the egg cell (zygote) after fertilization and the differentiation of cells into tissues and organs. This covers development including the formation of primitive organ systems, the creation of fundamental tissues, and cleavage. In humans the term embryo refers to the ball of dividing cells from the moment the blastocyst is implanted until the end of the eighth week after conception. Past the eighth week, the developing human is called a fetus.

History

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.

Vertebrate and invertebrate embryology

Many principles of embryology apply to both invertebrate animals as well as to vertebrates.^[1] Therefore, the study of invertebrate embryology has advanced the study of vertebrate embryology. However, there are many differences as well. For example, numerous invertebrate species release a larva before development is complete; at the end of the larval period, an animal for the first time comes to resemble an adult similar to it parents. Although invertebrate embryology is similar in some ways for different invertebrate animals, there are also countless variations. For instance, while spiders proceed directly from egg to adult form many insects develop through at least one larval stage.

Neuroembryology

Main article: Neural development

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.

Footnotes

1. ^ Parker, Sybil. "Invertebrate Embryology," McGraw-Hill Encyclopedia of Science & Technology (McGraw-Hill 1997).

References

UNSW Embryology Large resource of information and media
http://www2.merriam-webster.com/cgi-bin/mwmednlm?book=Medical&va=embryo Definition of embryo according to Webster

External links

Embryo Research UK philosophy and ethics website discussing the ethics of embryology
Human embryo research Canadian website covering the ethics of human embryo research
University of Indiana's Human Embryology Animations

• • [ e] Human development of embryo and development of fetus (some dates are approximate - see Carnegie stages and a timeline)
Week 1	Zygote - Morula - Blastomere - Blastula/Blastosphere/Blastocyst/Blastocoele - Inner cell mass
Week 2	Bilaminar disc (Hypoblast, Epiblast) - Archenteron/Primitive streak
Week 3 (Trilaminar embryo)	Primitive knot/Blastopore - Primitive groove - Gastrula/Gastrulation Germ layer: Ectoderm (Neuroectoderm) - Endoderm - Mesoderm (Chorda-, Paraxial, Intermediate, Lateral plate) - Splanchnopleure/Somatopleure Somite/Somitomere (Sclerotome, Myotome, Dermatome)
Uterine support	Allantois - Trophoblast (Cytotrophoblast, Syncytiotrophoblast, Gestational sac) - Yolk sac - Vitelline duct - Placenta - Umbilical cord (Umbilical artery, Umbilical vein, Wharton's jelly) - Amniotic sac (Amnion, Chorion) - Decidua - Decidual cells - Intervillous space - Chorionic villi
Branchial region	Branchial arch (1st/Meckel's cartilage, 2nd)/Branchial pouch - Cervical sinus - Lateral lingual swelling - Tuberculum impar - Frontonasal prominence - Olfactory pit - Nasal processes - Globular process - Primitive palate
Histogenesis and organogenesis	Glands: Thyroglossal duct Limb development: Limb bud - Apical ectodermal ridge/AER

• • [ e] Prenatal development/Mammalian development of digestive system
Gut	Foregut - Midgut - Hindgut
Mesentery	Dorsal mesentery - Ventral mesentery
Other	Stomodeum - Proctodeum - Rathke's pouch - Septum transversum - Pancreatic bud - Buccopharyngeal membrane

• • [ e] Prenatal development/mammalian embryogenesis - Development of the urinary and reproductive organs
General Urinary/Reproductive system	Cloacal membrane - Urogenital folds - Urethral groove - Urogenital sinus
Kidney development	Pronephros - Mesonephros - Ureteric bud - Metanephric blastema
Fetal genital development	Pronephric duct - Wolffian duct - Mllerian duct - Gubernaculum - Labioscrotal folds - Genital tubercle - Gonadal ridge - Sex cord - Cortical cords

• • [ e] Prenatal development/Mammalian development of nervous system
General neural development/Neurulation	Neurula - Notochord - Neural folds - Neuroectoderm - Neural plate - Neural groove Neural crest - Neural tube (Neuromere/Rhombomere, Cephalic flexure)
Eye development	Optic vesicles - Optic stalk - Optic cup
Auditory development	Auditory vesicle - Auditory pit

• • [ e] Prenatal development/Mammalian development of circulatory system
Heart development	atria (Primitive atrium, Atrial canal) - ventricles (Primitive ventricle, Bulbus cordis) - ostia (Ostium primum, Foramen ovale) - septa (Septum primum, Septum secundum, Septum intermedium, Endocardial cushions) - Sinus venosus - Truncus arteriosus
Vascular	arteries: Dorsal aorta - Aortic arches - Vitelline arteries - Ductus arteriosus - Umbilical artery veins: Cardinal veins - Ducts of Cuvier - Vitelline veins - Ductus venosus - Umbilical vein

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For other meanings see Zygote (disambiguation).

A zygote (Greek: ζυγωτόν) is a cell that is the result of fertilization.
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worldwide view.

2nd millennium
Centuries: 19th century - 20th century - 21st century

1920s 1930s 1940s - 1950s - 1960s 1970s 1980s
1950 1951 1952 1953 1954
1955 1956 1957 1958 1959

- -
- The 1950s
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James Dewey Watson

James D. Watson
Born March 06 1928 (age 79)
Chicago, Illinois, U.S.
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Francis Harry Compton Crick

Francis Harry Compton Crick
Born 8 May 1916
Weston Favell, Northamptonshire, England
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Rosalind Elsie Franklin (25 July, 1920 Kensington, London – 16 April, 1958 Chelsea, London) was an English biophysicist and crystallographer who made important contributions to the understanding of the fine structures of DNA, viruses, coal and graphite.
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Maurice Wilkins

Maurice Wilkins
Born November 15 1916
Pongaroa, Wairarapa, New Zealand
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Molecular biology is the study of biology at a molecular level. The field overlaps with other areas of biology and chemistry, particularly genetics and biochemistry. Molecular biology chiefly concerns itself with understanding the interactions between the various systems of a cell,
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Developmental Biology is the official journal of the Society for Developmental Biology. It publishes research on the mechanisms of development, differentiation, and growth in animals and plants at the molecular, cellular, and genetic levels.
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larva (Latin; plural larvae) is a juvenile form of animal with indirect development, undergoing metamorphosis (for example, insects or amphibians).

The larva can look completely different from the adult form, for example, a caterpillar differs from a butterfly.
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The study of neural development draws on both neuroscience and developmental biology to describe the cellular and molecular mechanisms by which complex nervous systems emerge during embryonic development and throughout life.
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nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and also stops input from the senses, and initiates actions. Prominent parts of a nervous system include neurons and nerves, which are used in coordination.
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In human embryology, formation of neural plate is the first step of neurulation. It is created by a flat thickening opposite to the primitive streak.

As it develops, it becomes surrounded by neural folds, which eventually create the cylindrical neural tube.
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The ectoderm is the start of a tissue that covers the body surfaces. It emerges first and forms from the outermost of the germ layers.

What forms from it (general)?

Nervous system
Outer part of integument

What forms from it (vertebrates)?

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Ontogeny (also ontogenesis or morphogenesis) describes the origin and the development of an organism from the fertilized egg to its mature form. Ontogeny is studied in developmental biology.
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Embryogenesis is the process by which the embryo is formed and develops. It starts with the fertilization of the ovum, egg, which, after fertilization, is then called a zygote.
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The theory of recapitulation, also called the biogenetic law, embryological parallelism or ontogeny recapitulates phylogeny, is a theory in biology which attempts to explain apparent similarities between humans and other animals.
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Prenatal development is the process in which an embryo or fetus (or foetus) gestates during pregnancy, from fertilization until birth. Often, the terms fetal development, foetal development, or embryology are used in a similar sense.
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Human embryogenesis is the process of cell division and cellular differentiation of the human embryo during early prenatal development. It spans from the moment of fertilization to the end of the 8th week of gestational age, whereafter it is called a fetus.
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fetus (or foetus, or fœtus) is a developing mammal or other viviparous vertebrate, after the embryonic stage and before birth. The plural is fetuses (foetuses, fœtuses) or, very rarely, foeti.
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In embryology, Carnegie stages are a standardized system of 23 stages used to provide a unified developmental chronology of the vertebrate embryo.

The stages are delineated through the development of structures, not by size or the number of days of development, and so the
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For other meanings see Zygote (disambiguation).

A zygote (Greek: ζυγωτόν) is a cell that is the result of fertilization.
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A morula (Latin "morus", mulberry) is an embryo at an early stage of embryonic development, consisting of approximately 12-32 cells (called blastomeres) in a solid ball contained within the zona pellucida.
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A blastomere is a type of cell produced by division of the egg after fertilization.

Human blastomere

In humans, blastomere formation begins immediately following fertilization and continues through the first week of embryonic development.
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The blastula is an early stage of embryonic development in animals. It is also called blastosphere. It is produced by cleavage of a fertilized ovum and consists of a spherical layer of around 128 cells surrounding a central fluid-filled cavity called the blastocoel.
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