関: celomic、coelom、coelomic

WordNet

a cavity in the mesoderm of an embryo that gives rise in humans to the pleural cavity and pericardial cavity and peritoneal cavity (同)coelom, celoma

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/04/02 18:42:36」(JST)

wiki en

Picture of human body cavities — dorsal body cavity to the left and ventral body cavity to the right.

By the broadest definition, a body cavity is any fluid-filled space in a multicellular organism, other than those of vessels (such as blood vessels and lymph vessels). However, the term usually refers to the space located between an animal’s outer covering (epidermis), and the outer lining of the gut cavity, where internal organs develop. "The human body cavity", normally refers to the ventral body cavity, because it is by far the largest one in volume.

Grouping

The type of body cavity places an organism into one of three groups:^[1]

Coelomates or Coelomata (also known as eucoelomates — "true coelom") have a fluid filled body cavity called a coelom (pron.: /ˈsiːləm/) with a complete lining called peritoneum derived from mesoderm (one of the three primary tissue layers). The complete mesoderm lining allows organs to be attached to each other so that they can be suspended in a particular order while still being able to move freely within the cavity. Most bilateral animals, including all the vertebrates, are coelomates.

Pseudocoelomate animals have a pseudocoelom (literally “false cavity”), which is a fully functional body cavity. Tissue derived from mesoderm only partly lines the fluid filled body cavity of these animals. Thus, although organs are held in place loosely, they are not as well organized as in a coelomate. All pseudocoelomates are protostomes; however, not all protostomes are pseudocoelomates. An example of a Pseudocoelomate is the roundworm. Pseudocoelomate animals are also referred to as Hemocoel and Blastocoelomate.

Acoelomate animals, like flatworms, have no body cavity at all. Organs have direct contact with the epithelium. Semi-solid mesodermal tissues between the gut and body wall hold their organs in place.

Coelom

Main article: Coelom

A coelom is a cavity lined by an epithelium derived from mesoderm. Organs formed inside a coelom can freely move, grow, and develop independently of the body wall while fluid cushions and protects them from shocks.

Arthropods and mollusks have a reduced (but still true) coelom. Their principal body cavity is the hemocoel of an open circulatory system.

Mammalian embryos develop two coelomic cavities: the intraembryonic coelom and the extraembryonic coelom (or chorionic cavity). The intraembryonic coelom is lined by somatic and splanchnic lateral plate mesoderm, while the extraembryonic coelom is lined by extraembryonic mesoderm. The intraembryonic coelom is the only cavity that persists in the mammal at term, which is why its name is often contracted to simply coelomic cavity. Subdividing the coelomic cavity into compartments, for example, the pericardial cavity / pericardium, where the heart develops, simplifies discussion of the anatomies of complex animals.

Formation

Coelom formation begins in the gastrula stage. The developing digestive tube of an embryo forms as a blind pouch called the archenteron.

In Protostomes the coleom forms by a process known as schizocoely. The archenteron initially forms, and the mesoderm splits into two layers: the first attaches to the body wall or ectoderm, forming the parietal layer and the second surrounds the endoderm forming the visceral layer or alimentary canal. The space between the parietal layer and the visceral layer is known as the coelom or body cavity. In Deuterostomes, the coelom forms by enterocoely: mesoderm buds from the walls of the archenteron and hollows to become the coelomic cavities.

Origins

The origin of the coelom is uncertain. The oldest known animal to have had a body cavity is Vernanimalcula.

Current evolutionary theories:

The acoelomate theory
- Coelom evolved from an acoelomate ancestor.
The enterocoel theory
- Coelom evolved from gastric pouches of cnidarian ancestors.
- Supported by research on flatworms and small worms recently discovered in marine fauna ("coelom")

Pseudocoelom

In some protostomes, the embryonic blastocoele persists as a body cavity. These protostomes have a fluid filled main body cavity unlined or partially lined with tissue derived from mesoderm. This fluid-filled space surrounding the internal organs serves several functions like distribution of nutrients and removal of waste or supporting the body as a hydrostatic skeleton.

Pseudocoelomates

Pseudocoelomate is no longer considered a valid taxonomic group, since it is not monophyletic. However, it is still used as a descriptive term.

A pseudocoelomate is any invertebrate animal with a three-layered body and a pseudocoel. The coelom was apparently lost or reduced as a result of mutations in certain types of genes that affected early development. Thus, pseudocoelomates evolved from coelomates.^[2]

Important characteristics:

lack a vascular blood system
- diffusion and osmosis circulate nutrients and waste products throughout the body.
lack a skeleton
- hydrostatic pressure gives the body a supportive framework that acts as a skeleton.
no segmentation
body wall
- epidermis and muscle
- often syncytial
- usually covered by a secreted cuticle
most are microscopic
parasites of almost every form of life (although some are free living)
eutely in some
loss of larval stage in some
possibly pedomorphism

Examples of pseudocoelomates

Nematoda (roundworms)
Rotifera (rotifers)
Kinorhyncha
Nematomorpha, nematomorphs, or horsehair worms
Gastrotricha
Loricifera
Priapulida
Acanthocephala (spiny-headed worms)
Aschelminth animals
Entoprocta

No coelom (Acoelomate)

Lacking a fluid filled body cavity presents some serious disadvantages. Fluids do not compress, while the tissue surrounding the organs of these animals will compress. Therefore, acoelomate organs are not protected from crushing forces applied to the animal’s outer surface.

Organisms showing acoelomate formation include the platyhelminthes (flatworms, tapeworms etc.), the cnidarians (jellyfish and allies), and the ctenophores (comb jellies). The coelom can be used for diffusion of gases and metabolites etc. These creatures do not have this need, as the surface area to volume ratio is large enough to allow absorption of nutrients and gas exchange by diffusion alone, due to dorso-ventral flattening.

References

^ "Animals III — Pseudocoelomates and Protostome Coelomates".
^ Evers, Christine A., Lisa Starr. Biology:Concepts and Applications. 6th ed. United States:Thomson, 2006. ISBN 0-534-46224-3.

External links

Further discussion
"coelom." The Columbia Electronic Encyclopedia, Sixth Edition. Columbia University Press., 2003. Answers.com 02 . 2006. http://www.answers.com/topic/body-cavity
Bioweb at UWLAX Zoolab
Glasgow University Science Museum

English Journal

Early second-trimester diagnosis of body stalk anomaly by fetal magnetic resonance imaging.

Higuchi T1, Sato H, Iida M, Kim SH, Narimatsu Y, Tanaka M.
Japanese journal of radiology.Jpn J Radiol.2013 Apr;31(4):289-92. doi: 10.1007/s11604-013-0182-z. Epub 2013 Feb 6.
We report a case of body stalk anomaly detected prenatally by fetal magnetic resonance imaging (MRI) at 14 weeks' gestation. A 29-year-old woman was followed during her first pregnancy. At 11-12 weeks' gestation, our sonographic images showed multiple fetal deformities. An abdominal wall defect was
PMID 23385378

Immunohistochemical expression of Wilms' tumor protein (WT1) in developing human epithelial and mesenchymal tissues.

Parenti R1, Perris R, Vecchio GM, Salvatorelli L, Torrisi A, Gravina L, Magro G.
Acta histochemica.Acta Histochem.2013 Jan;115(1):70-5. doi: 10.1016/j.acthis.2012.04.006. Epub 2012 Jun 4.
The Wilms' tumor (WT1) gene and its protein product are known to exhibit a dynamic expression profile during development and in the adult organism. Apart from a nuclear expression observed in the urogenital system, its precise localization in other developing human tissues is still largely unknown.
PMID 22673530

The tale of spring water cysts: a historical outline of surgery for congenital pericardial diverticula and cysts.

Schweigert M1, Dubecz A, Beron M, Ofner D, Stein HJ.
Texas Heart Institute journal.Tex Heart Inst J.2012;39(3):330-4.
Congenital pericardial diverticula and cysts are extremely uncommon lesions within the anterior mediastinum. Both lesions derive from the pericardial celom and represent different stages of a common embryogenesis. Initial reports date from the 19th century. Surgical pioneers were Otto Pickhardt, who
PMID 22719140

Japanese Journal

「受洗タタール」から「クリャシェン」へ--現代ロシアにおける民族復興の一様態

櫻間瑛
スラヴ研究 (56), 127-155[含ロシア語文要旨], 2009-00-00
После перестройки на территории СССР возникло немало различных национальных и этнических движений. Несмотря на то, что данной теме уже было посвящено довольно много научных работ, все еще остается нер …
NAID 120001498442

語り手の不明瞭化 : 『アントーノフカのりんご』バリアントの比較

加藤敏
Slavistika : 東京大学大学院人文社会系研究科スラヴ語スラヴ文学研究室年報 20, 34-49, 2005-03-31
И. А. Бунин при издании сборников своих произведений исправлял свой рассказ <<Антоновские яблокиО>> несколько раз. При этом он занимался главным образом сокращением текста, т. е. редко доб …
NAID 110006405652

指小接尾辞-#к(-)の意味構造

中尾裕子
ロシア語ロシア文学研究 (36), 93-101, 2004-09-15
Многие исследователи неоднократно отмечали полисемантический характер диминутивного суффикса -#к(-), однако попытка упорядочить семантическую структуру данного суффикса в целом почти не предпринималас …
NAID 110001247120