Embryology is the study of the development of an embryo. An embryo (from Greek:, plural, lit "that which grows" from en- "in" + bryein "to swell be full" is a multicellular An embryo is defined as any organism in a stage before birth or hatching, or in plants, before germination occurs. Germination is the process whereby growth emerges from a period of dormancy
Embryology refers to the development of the fertilized egg cell (zygote) and its differentiation into tissues and organs. For other meanings see Zygote (disambiguation. A zygote (from Greek ζυγωτός zugōtos "joined" or "yoked" After cleavage, the dividing cells, or morula, becomes a hollow ball, or blastula, which develops a hole or pore at one end. A morula ( Latin "morus" Mulberry) is an Embryo at an early stage of Embryonic development, consisting of approximately 12-32 The blastula is an early stage of Embryonic development in Animals It is also called blastosphere
In animals, the blastula develops in one of two ways that divides the whole animal kingdom into two halves. The blastula is an early stage of Embryonic development in Animals It is also called blastosphere If in the blastula the first pore (blastopore) becomes the mouth of the animal, it is a protostome; if the first pore becomes the anus then it is a deuterostome. The blastula is an early stage of Embryonic development in Animals It is also called blastosphere A blastopore is an opening into the Archenteron during the Embryonic stages of an organism Protostomia (from the Greek: mouth first) are a Taxon of Animals Together with the Deuterostomes and a few smaller phyla Deuterostomes (taxonomic term Deuterostomia; from the Greek "second mouth" are a superphylum of Animals They are a subtaxon of the The protostomes include most invertebrate animals, such as insects, worms and molluscs, while the deuterostomes includes more advanced animals including the vertebrates. Protostomia (from the Greek: mouth first) are a Taxon of Animals Together with the Deuterostomes and a few smaller phyla An invertebrate is an Animal lacking a Vertebral column. The group includes 98% of all animal Species — all animals except those in the Chordate Deuterostomes (taxonomic term Deuterostomia; from the Greek "second mouth" are a superphylum of Animals They are a subtaxon of the Vertebrates are members of the Subphylum Vertebrata, Chordates with backbones or spinal columns The grouping sometimes includes In due course, the blastula changes into a more differentiated structure called the gastrula. The blastula is an early stage of Embryonic development in Animals It is also called blastosphere Gastrulation is a phase early in the development of animal Embryos during which the morphology of the embryo is dramatically restructured by Cell migration.
The gastrula with its blastopore soon develops three distinct layers of cells (the germ layers) from which all the bodily organs and tissues then develop:
- The innermost layer, or endoderm, gives rise to the digestive organs, lungs and bladder. Gastrulation is a phase early in the development of animal Embryos during which the morphology of the embryo is dramatically restructured by Cell migration. A blastopore is an opening into the Archenteron during the Embryonic stages of an organism A germ layer is a collection of cells formed during animal Embryogenesis. Endoderm, (sometimes called Entoderm) is one of the Germ layers formed during animal Embryogenesis.
- The middle layer, or mesoderm, gives rise to the muscles, skeleton and blood system. One of the three Germ layers found in the Embryos of Animals more complex than Cnidarians making them Triploblastic.
- The outer layer of cells, or ectoderm, gives rise to the nervous system and skin. The ectoderm is the start of a tissue that covers the body surfaces
In humans, the term embryo refers to the ball of dividing cells from the moment the zygote implants itself in the uterus wall until the end of the eighth week after conception. For other meanings see Zygote (disambiguation. A zygote (from Greek ζυγωτός zugōtos "joined" or "yoked" The uterus (from the Latin word for womb) is the major Female reproductive organ of most Mammals including Humans One end the Beyond the eighth week, the developing human is then called a fetus. Embryos in many species often appear similar to one another in early developmental stages. The reason for this similarity is because species have adapted into the environment of pregnancy. These similarities among species are called analogous structures, which are structures that have the same or similar function and mechanism, but evolved separately. Two structures in biology are said to be analogous if they perform the same or similar function by a similar mechanism but evolved separately
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History
As recently as the 18th century, the prevailing notion in human embryology was preformation: the idea that the egg or sperm contains an embryo--a preformed, miniature infant, or "homunculus"--that simply becomes larger during development. Preformationism is the theory that all Organisms were created at the same time and that succeeding generations grow from homunculi, Animalcules or other The competing explanation of embryonic development was epigenesis, originally proposed 2,000 years earlier by Aristotle. According to epigenesis, the form of an animal emerges gradually from a relatively formless egg. As microscopy improved during the 19th century, biologists could see that embryos took shape in a series of progressive steps, and epigenesis displaced preformation as the favored explanation among embryologists. Microscopy is the technical field of using microscopes to view samples or objects [1]
Modern embryological pioneers include Gavin de Beer, Charles Darwin, Ernst Haeckel, J.B.S. Haldane, and Joseph Needham, while much early embryology came from the work of Aristotle and the great Italian anatomists: Aldrovandi, Aranzio, Leonardo da Vinci, Marcello Malpighi, Gabriele Falloppia, Girolamo Cardano, Emilio Parisano, Fortunio Liceti, Stefano Lorenzini, Spallanzani, Enrico Sertoli, Mauro Rusconi, etc. Sir Gavin Rylands de Beer FRS (1899–1972 was a British Evolutionary embryologist. Charles Robert Darwin (February 12 1809 &ndash April 19 1882 was an English naturalist, who realised and demonstrated that all Species of life Ernst Heinrich Philipp August Haeckel ( February 16, 1834 — August 9, 1919)also written von Haeckel, was an eminent German John Burdon Sanderson Haldane FRS ( 5 November 1892 &ndash 1 December 1964) known as Jack (but who used 'J Noel Joseph Terence Montgomery Needham, CH, FRS, FBA ( December 9, 1900 – March 24 1995) was a British Aristotle (Greek Aristotélēs) (384 BC – 322 BC was a Greek philosopher a student of Plato and teacher of Alexander the Great. Italy (Italia officially the Italian Republic, (Repubblica Italiana is located on the Italian Peninsula in Southern Europe, and on the two largest Leonardo di ser Piero da Vinci ( April 15 1452 – May 2 1519 was an Italian Polymath, having been a scientist Mathematician, Engineer Marcello Malpighi ( March 10, 1628 - September 30, 1694) was an Italian doctor who gave his name to several physiological features Fortunio Liceti (1577-1657 also known as Fortunius Licetus, was an Italian Scientist. Lazzaro Spallanzani ( January 10, 1729 - February 12, 1799) was an Italian Biologist whose research of Biogenesis Enrico Sertoli ( June 6 1842 - January 28, 1910) was an Italian Physiologist and Histologist who was a native of Sondrio [2] Other important contributors include William Harvey, Kaspar Friedrich Wolff, Pander, Karl Ernst von Baer, and August Weismann. William Harvey ( April 1, 1578 – June 3, 1657) was an English Physician who is credited with being the first in Caspar Friedrich Wolff ( January 18, 1733 &ndash February 22, 1794) was a German Physiologist and one of the founders of Karl Ernst von Baer ( -) was a Baltic German Biologist and a founding father of Embryology. Friedrich Leopold August Weismann (Birth January 17, 1834 in Frankfurt am Main; Death
After the 1950s, with the DNA helical structure being unravelled and the increasing knowledge in the field of molecular biology, developmental biology emerged as a field of study which attempts to correlate the genes with morphological change; and so tries to determine which genes are responsible for each morphological change that takes place in an embryo, and how these genes are regulated. The 1950s Decade refers to the years of 1950 to 1959 inclusive Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Molecular biology is the study of Biology at a molecular level Developmental Biology is the official journal of the Society for Developmental Biology.
Vertebrate and invertebrate embryology
Many principles of embryology apply to both invertebrate animals as well as to vertebrates. [3] 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. A larva ( Latin; plural larvae) is a juvenile form of Animal with indirect development, undergoing Metamorphosis (for example 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.
Modern embryology research
Currently, embryology has become an important research area for studying the genetic control of the development process (e. g. morphogens), its link to cell signalling, its importance for the study of certain diseases and mutations and in links to stem cell research. A morphogen is a substance governing the pattern of tissue development and in particular the positions of the various specialized cell types within a tissue Cell signaling is part of a Complex system of Communication that governs basic cellular activities and coordinates cell actions In biology mutations are changes to the Nucleotide sequence of the Genetic material of an organism Stem cells are cells found in most if not all multi-cellular Organisms.
See also
- Ontogeny
- Embryogenesis
- Recapitulation theory
- Prenatal development
- Protostomes
- Deuterostomes
- Germ layers
- Epigenesis (biology)
- Developmental biology
- Cell signalling
- Hedgehog signaling pathway
- Morphogens
- Embryo drawing
References
- UNSW Embryology Large resource of information and media
- [1] Definition of embryo according to Webster
Further reading
- Scott F. Ontogeny, as opposed to Phylogeny, refers to the history of an organism from birth as opposed to its genetic makeup Embryogenesis is the process by which the Embryo is formed and develops The theory of recapitulation, also called the biogenetic law or embryological parallelism, and often expressed as Ontogeny recapitulates Phylogeny Prenatal development is the process in which an embryo or fetus (or foetus) gestates during Pregnancy, from fertilization Protostomia (from the Greek: mouth first) are a Taxon of Animals Together with the Deuterostomes and a few smaller phyla Deuterostomes (taxonomic term Deuterostomia; from the Greek "second mouth" are a superphylum of Animals They are a subtaxon of the A germ layer is a collection of cells formed during animal Embryogenesis. In Biology, epigenesis has at least two distinct meanings the unfolding development in an organism and in particular the development of a plant Developmental Biology is the official journal of the Society for Developmental Biology. Cell signaling is part of a Complex system of Communication that governs basic cellular activities and coordinates cell actions In a growing embryo cells develop differently in the head or tail end of the embryo the left or right and other positions A morphogen is a substance governing the pattern of tissue development and in particular the positions of the various specialized cell types within a tissue Embryo drawing refers to any representation of the Illustration of Embryos in their developmental sequence. Gilbert. Developmental Biology. Sinauer, 2003. ISBN 0-87893-258-5.
- Lewis Wolpert. Principles of Development. Oxford University Press, 2006. ISBN 0-19-927536-X.
- A Scientist’s Interpretation of References to Embryology in the Qur’an by Keith L. Moore, Ph. D. , F. I. A. C.
- Embryology and Human Creation between Quran & Science by Dr. Sharif Kaf Al-Ghazal (Aug 2004)
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
- What is a human admixed embryo?
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