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Information about Somite

Transverse section of half of a chick embryo of forty-five hours' incubation. The dorsal (back) surface of the embryo is towards the top of this page, while the ventral (front) surface is towards the bottom.
Dorsum of human embryo, 2.11 mm. in length. (The older term 'primitive segments' is used to identify the somites.)
subject #9 52
Carnegie stage9
Days20[1]
Precursorparaxial mesoderm
Gives rise todermatome, myotome, sclerotome
MeSH Somites
Dorlands/Elsevier s_15/12743985
In the developing vertebrate embryo, somites (or primitive segments in older texts) are masses of mesoderm distributed along the two sides of the neural tube and that will eventually become dermis (dermatome), skeletal muscle (myotome), and vertebrae (sclerotome).

Because the sclerotome differentiates before the other two structures, the term "dermomyotome" is sometimes used to describe the combined dermatome and myotome.[2]

Development

They originate from paraxial mesoderm which, towards the end of the third gestational week, becomes organized into loose masses of cells called somitomeres.

Driven by changes in the expression of adhesion molecules, somitomeres compact and bud off to form the somites.

Approximately 44 somites form and give rise to the bones of the face, vertebral column, associated muscles, and overlying dermis.

The final somite count in the cervical, thoracic, lumbar, and sacral is equal to the number of cranial nerves in that region (8, 12, 5, and 5, respectively.)[1]

In crustaceans

In crustacean biology, a somite is a segment of the hypothetical primitive crustacean body plan. In current crustaceans, several of those somites may be fused.

References

1. ^ The Third Week Of Life:. Retrieved on 2007-10-13.
2. ^ unc. Retrieved on 2007-10-19.
3. ^

Additional images


Chick embryo of thirty-three hours’ incubation, viewed from the dorsal aspect. X 30.


External links

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Human development of embryo and development of fetus (some dates are approximate - see Carnegie stages and a timeline)
Week 1Zygote - Morula - Blastomere - Blastula/Blastosphere/Blastocyst/Blastocoele - Inner cell mass
Week 2Bilaminar 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 supportAllantois - 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 regionBranchial 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 organogenesisGlands: Thyroglossal duct
Limb development: Limb bud - Apical ectodermal ridge/AER
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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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.
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Paraxial mesoderm is the area of mesoderm that forms just lateral to the neural tube on both sides.

It gives rise to the somitomeres/somites and mesoderm of the branchial arches.
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Dermatome may refer to:
  • Dermatome (instrument), a surgical instrument used to produce thin slices of skin
  • Dermatomic area, an area of skin that is supplied by a single pair of dorsal roots

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In vertebrate embryonic development, a myotome is a group of tissues formed from somites that develop into the body wall muscle.

Each myotome divides into a dorsal epaxial part and a ventral hypaxial part.
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A sclerotome is part of a somite, a structure in vertebrate embryonic development. Sclerotomes eventually differentiate into the vertebrae and most of the skull. The caudal half of one sclerotome fuses with the cranial half of the adjacent one to form each vertebra.
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Medical Subject Headings (MeSH) is a huge controlled vocabulary (or metadata system) for the purpose of indexing journal articles and books in the life sciences. Created and updated by the United States National Library of Medicine (NLM), it is used by the MEDLINE/PubMed
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Elsevier, the world's largest publisher of medical and scientific literature, forms part of the Reed Elsevier group. Based in Amsterdam, the company has substantial operations in the UK, USA and elsewhere.
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Vertebrata
Cuvier, 1812

Classes and Clades

See below
Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns.
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The germ layer mesoderm forms in the embryos of animals more complex than cnidarians, making them triploblastic. Mesoderm forms during gastrulation when some of the cells migrating inward to form the endoderm form an additional layer between the endoderm and the ectoderm.
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neural tube is the embryo's precursor to the central nervous system, which comprises the brain and spinal cord. The neural groove gradually deepens as the neural folds become elevated, and ultimately the folds meet and coalesce in the middle line and convert the groove into a
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Dermatome may refer to:
  • Dermatome (instrument), a surgical instrument used to produce thin slices of skin
  • Dermatomic area, an area of skin that is supplied by a single pair of dorsal roots

..... Click the link for more information.
In vertebrate embryonic development, a myotome is a group of tissues formed from somites that develop into the body wall muscle.

Each myotome divides into a dorsal epaxial part and a ventral hypaxial part.
..... Click the link for more information.
A sclerotome is part of a somite, a structure in vertebrate embryonic development. Sclerotomes eventually differentiate into the vertebrae and most of the skull. The caudal half of one sclerotome fuses with the cranial half of the adjacent one to form each vertebra.
..... Click the link for more information.
Paraxial mesoderm is the area of mesoderm that forms just lateral to the neural tube on both sides.

It gives rise to the somitomeres/somites and mesoderm of the branchial arches.
..... Click the link for more information.
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time (multiple gestations).
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In the developing vertebrate embryo, the somitomeres are loose masses of paraxial mesoderm derived cells that form along each side of the neural tube towards the end of the third gestational week.
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vertebral column (backbone or spine) is a column of 34 vertebrae, the sacrum, intervertebral discs, and the coccyx situated in the dorsal aspect of the torso, separated by spinal discs. It houses the spinal cord in its spinal canal.
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Cranial nerves are nerves that emerge directly from the brain in contrast to spinal nerves which emerge from segments of the spinal cord. Although thirteen cranial nerves in humans fit this description, twelve are conventionally recognized.
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crustaceans (Crustacea) are a large group of arthropods, comprising approximately 52,000 described species [1], and are usually treated as a subphylum [2].
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New South Wales University of Technology
Type Public
Endowment $914million [1]
Chancellor David Gonski
Vice-Chancellor Professor Fred Hilmer
Staff 6,500
Students 40,000
Location Kensington,
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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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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.
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Please help recruit one or [ improve this article] yourself. See the talk page for details.
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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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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
..... Click the link for more information.
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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For other meanings see Zygote (disambiguation).
A zygote (Greek: ζυγωτόν) is a cell that is the result of fertilization.
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