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Information about Body Cavity

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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. 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 body cavity" of human body cavities normally refers to the ventral body cavity, because it is by far the largest one in area.

The type of body cavity places an organism into one of these three groups:
  • Coelomate animals (also known as eucoelomates--"true coelom") have a fluid filled body cavity called a coelom (pronounced: /ˈsiləm/) 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 pseudocoel, (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. 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

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, 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 archenetron.

In Protostomes, a process known as schizocoelus happens: as the archenteron initially forms, the mesoderm splits to form the coelomic cavities. In Deuterostomes, a process known as eneterocoelus happens: the 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")

Pseudocoel

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 (Evers, 355).

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)

Examples of pseudocoelomates

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 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.

Platyhelminthes along with members of the phyla Nemertea (ribbon worms), lack a coelom* - a fluid-filled cavity between the outer body wall and the gut. These animals are described as being acoelomate* .

References

External links

Multicellular organisms are organisms consisting of more than one cell, and having differentiated cells that perform specialized functions. Most life that can be seen with the naked eye is multicellular, as are all members of the kingdoms Plantae and Animalia (except for
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Epidermis is the outermost layer of the skin. It forms the waterproof, protective wrap over the body's surface and is made up of stratified squamous epithelium with an underlying basal lamina.
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The human body consists of the following body cavities:
  • dorsal body cavity
  • cranial cavity, enclosed by the Skull and contains the brain, eyes, and ears.

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ventral body cavity is a human body cavity that is in the anterior (front) aspect of the human body. It is made up of the thoracic cavity, and the abdominopelvic cavity. The abdominopelvic cavity is further separated into the abdominal cavity and pelvic cavity, but there is no
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International Phonetic Alphabet

Note: This page may contain IPA phonetic symbols in Unicode.

The International
Phonetic Alphabet
History
Nonstandard symbols
Extended IPA
Naming conventions
IPA for English The
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In higher vertebrates, the peritoneum is the serous membrane that forms the lining of the abdominal cavity - it covers most of the intra-abdominal organs. It is composed of a layer of mesothelium supported by a thin layer of connective tissue.
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germ layer is a collection of cells, formed during animal embryogenesis. Germ layers are only really pronounced in the vertebrates. However, all animals more complex than sponges (eumetazoans and ) produce two or three primary tissue layers
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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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Protostomia

Groups
  • Ecdysozoa
  • Lophotrochozoa
  • Platyzoa


Protostomes (from the Greek: mouth first) are a taxon of animals.
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A Hemocoel is a cavity or series of spaces between the organs of organisms with open circulatory systems like most arthropods and mollusks. A combination of blood, lymph, and interstitial fluid called hemolymph circulates through the hemocoel.
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A blastocoel(e) or blastocele (also called blastocyst cavity,[1] cleavage cavity or segmentation cavity) is the fluid-filled central region of a blastocyst.
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Platyhelminthes
Gegenbaur, 1859

Classes

Monogenea
Trematoda
Cestoda
Turbellaria

The flatworms (Phylum Platyhelminthes from the Greek platy, meaning "flat" and helminth
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epithelium is a tissue composed of a layer of cells. Epithelium lines both the outside (skin) and the inside cavities and lumen of bodies. The outermost layer of our skin is composed of dead stratified squamous, keratinized epithelial cells.
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epithelium is a tissue composed of a layer of cells. Epithelium lines both the outside (skin) and the inside cavities and lumen of bodies. The outermost layer of our skin is composed of dead stratified squamous, keratinized epithelial cells.
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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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Arthropoda
Latreille, 1829

Subphyla and Classes
  • Subphylum Trilobitomorpha
  • Trilobita - trilobites (extinct)
  • Subphylum Chelicerata

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Mollusca
Linnaeus, 1758

Classes

Caudofoveata
Aplacophora
Polyplacophora
Monoplacophora
Bivalvia
Scaphopoda
Gastropoda
Cephalopoda
† Rostroconchia
† Helcionelloida
† ?Bellerophontida
The molluscs
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The intraembryonic coelom (or somatic coelom) is a a portion of the conceptus forming in the mesoderm.

It briefly has a connection with the extraembryonic coelom.

External links

  • http://www.embryology.ch/anglais/hdisqueembry/triderm09.

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The extraembryonic coelom is a portion of the conceptus consisting of a cavity between Heuser's membrane and the hypoblast.

It divides the two layers of extraembryonic mesoderm (splanchnopleuric and somatopleuric).

It is also known as the "chorionic cavity".
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The pericardium is a double-walled sac that contains the heart and the roots of the great vessels.

Layers

There are two layers to this sac: the fibrous pericardium and the serous pericardium.
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Anatomy (from the Greek ἀνατομία anatomia, from ἀνατέμνειν
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The archenteron is known as the primitive gut that forms during gastrulation in the developing blastula. It develops into the digestive tract of an animal.

Formation of the Archenteron

[See Gastrulation]
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Protostomia

Groups
  • Ecdysozoa
  • Lophotrochozoa
  • Platyzoa


Protostomes (from the Greek: mouth first) are a taxon of animals.
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The archenteron is known as the primitive gut that forms during gastrulation in the developing blastula. It develops into the digestive tract of an animal.

Formation of the Archenteron

[See Gastrulation]
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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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Deuterostomia
Grobben, 1908

Phyla
  • Xenoturbellida (2 species)
  • Vetulicolia † (8 species)
  • Echinodermata (20,000 species)
  • Hemichordata (71 species)
  • Chordata (63,000+ species)


Deuterostomes (taxonomic term:
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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.
..... Click the link for more information.
The archenteron is known as the primitive gut that forms during gastrulation in the developing blastula. It develops into the digestive tract of an animal.

Formation of the Archenteron

[See Gastrulation]
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Vernanimalcula has been described as the earliest known member of the Bilateria (animals with bilateral symmetry). It lived some 580 to 600 million years ago. It was between 0.1 and 0.
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