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Encyclopedia > Pseudocoelom

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. Multicellular organisms are those organisms consisting of more than one cell, and having differentiated cells that perform specialized functions. ... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anenomes) Placozoa (trichoplax) Subregnum Bilateria (bilateral symmetry) Acoelomorpha (basal) Orthonectida (parasitic to flatworms, echinoderms, etc. ... Epidermis could refer to: In plants, the outermost layer of cells covering the leaves and young parts of a plant is the epidermis. ...


The type of body cavity places an organism into one of these three groups:

  • Coelomate animals have a fluid filled body cavity called a coelom (pronounced: sē'ləm) with a complete lining called peritoneum derived from mesoderm (one of the three primary tissue layers). Most bilateral animals, including all the vertebrates), are coelomates.
  • Pseudocoelomate animals have a pseudocoel (literally “false cavity”). Tissue derived from mesoderm only partly lines the fluid filled body cavity of these animals. All pseudocoelomates are protostomes; however, not all protostomes are pseudocoelomate.
  • Acoelomate animals, like flatworms, have no body cavity at all. Semi-solid mesodermal tissues between the gut and body wall hold their organs in place.

Contents

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 has been suggested that organogenesis be merged into this article or section. ... Subgroups †Conodonta Hyperoartia   Petromyzontidae (lampreys) †Pteraspidomorphi †Thelodonti †Anaspida †Cephalaspidomorphi   †Galeaspida   †Pituriaspida   †Osteostraci Gnathostomata (jawed vertebrates)   †Placodermi   Chondrichthyes (cartilaginous fish)   †Acanthodii   Osteichthyes (bony fish)     Actinopterygii (ray-finned fish)     Sarcopterygii (lobe-finned fish)       Actinistia (coelacanths)       Dipnoi (lungfish)       Tetrapoda (four-limbed vertebrates)         Amphibia (amphibians)         Amniota (amniotic embryo)           Sauropsida (reptiles)             Aves (birds)           Synapsida (mammal... Phyla Mollusca Arthropoda Annelida Protostomes (from the Greek: first the mouth) are a superphylum of animals in the taxonomic group bilateria, and include animals such as arthropods, mollusks, and nematodes. ... Classes Monogenea Trematoda Cestoda Turbellaria The flatworms (Platyhelminthes, Greek platy: flat; helminth: worm) are a phylum of relatively simple soft-bodied invertebrate animals. ...


Coelom

A coelom is a cavity lined by an epithelium derived from mesenchyme. Organs formed inside a coelom can freely move, grow, and develop independently of the body wall while fluid cushions and protects them from shocks. This key innovation evolved hundreds of millions of years ago and led to the evolution of nearly all large, complex animals. In zootomy, epithelium is a tissue composed of a layer of cells. ... Mesenchyme (also known as embryonic connective tissue) is the mass of tissue that develops mainly from the mesoderm (the middle layer of the trilaminar germ disc) of an embryo. ...


Arthropods and mollusks have a reduced (but still true) coelom. Their principal body cavity is the hemocoel of an open circulatory system. Subphyla and Classes Subphylum Trilobitomorpha Trilobita - Trilobites (extinct) Subphylum Chelicerata Arachnida - Spiders, Scorpions, etc. ... Classes Caudofoveata Aplacophora Polyplacophora Monoplacophora Bivalvia Scaphopoda Gastropoda Cephalopoda The molluscs or mollusks are the large and diverse phylum Mollusca, which includes a variety of familiar creatures well-known for their decorative shells or as seafood. ... An open circulatory system is an arrangement of internal transport in which blood bathes the organs directly and there is no distinction between blood and interstitial fluid. ...


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. The pericardium is a double-walled sac that contains the heart and the roots of the great vessels. ... Anatomical drawing of the human muscles from the Encyclopédie. ...


Formation

In animals of the phyla Annelida, Mollusca, and Arthropoda, the mesoderm forms as a mass of tissue from special embryonic cells between the ectoderm and the endoderm. This mesodermal mass then splits to form the coelom. Phylum (plural: phyla) is a taxon used in the classification of life, adopted from the Greek phylai the clan-based voting groups in Greek city-states. ... Classes and subclasses Class Polychaeta (paraphyletic?) Class Clitellata    Oligochaeta - Earthworms and others    Acanthobdellida    Branchiobdellida    Hirudinea - Leeches Class Myzostomida Class Archiannelida (polyphyletic) Class Echiura *Some authors consider the subclasses under Clitellata to be classes The annelids, collectively called Annelida (from Latin annellus little ring), are a large phylum of animals, comprising...


In deuterostomes, mesoderm arises out of folds in the developed endoderm which pinch off to form the coelom. Phyla Echinodermata Hemichordata Chordata Chaetognatha Deuterostomes (taxonomic term: Deuterostomia; from the Greek: other mouth) are a superphylum of animals. ...


Origins

The origin of the coelom is uncertain. The oldest known animal to have had a body cavity is Vernanimalcula. The oldest known examples of a bilaterian, bilateral animals. ...


Current evolutionary theories: A speculatively rooted phylogenetic tree of all living things, based on rRNA gene data, showing the separation of the three domains, bacteria, archaea, and eukaryotes, as described initially by Carl Woese. ...

  • 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. Phyla Mollusca Arthropoda Annelida Protostomes (from the Greek: first the mouth) are a superphylum of animals in the taxonomic group bilateria, and include animals such as arthropods, mollusks, and nematodes. ... A blastocoel(e) or blastocele or cleavage cavity or segmentation cavity is the central region of a blastula (or blastosphere). ... In biology, an organ (Latin: organum, instrument, tool) is a group of tissues, which perform a specific function or group of functions. ... A hydrostatic skeleton is one in which the bodys shape and/or function is maintained by an incompressible fluid such as blood or hemolymph. ...


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). Taxonomy (from Greek verb tassein = to classify and nomos = law, science, cf economy) may refer to: the science of classifying living things (see alpha taxonomy) a classification Initially taxonomy was only the science of classifying living organisms, but later the word was applied in a wider sense, and may also... In phylogenetics, a group is monophyletic (Greek: of one stem) if all organisms in that group are known to have developed from a common ancestral form, and all descendants of that form are included in the group. ... Invertebrate is a term coined by Jean-Baptiste Lamarck to describe any animal without a spinal column. ... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anenomes) Placozoa (trichoplax) Subregnum Bilateria (bilateral symmetry) Acoelomorpha (basal) Orthonectida (parasitic to flatworms, echinoderms, etc. ... In biology, mutations are changes to the genetic material (usually DNA or RNA). ... This stylistic schematic diagram shows a gene in relation to the double helix structure of DNA and to a chromosome (right). ... By the broadest definition, a body cavity is any fluid filled space in a multicellular organism. ...


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.
  • complete digestive system
    • begins at a mouth and ends at an anus
  • 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)

Schematic drawing of the effects of diffusion through a semipermeable membrane. ... Osmosis is the diffusion of a solvent through a semipermeable membrane from a region of low solute concentration to a region of high solute concentration. ...

Examples of pseudocoelomates

Classes Adenophorea    Subclass Enoplia    Subclass Chromadoria Secernentea    Subclass Rhabditia    Subclass Spiruria    Subclass Diplogasteria The roundworms (Phylum Nematoda from Gr. ... Classes Seisonoidea Bdelloidea Monogononta The rotifers make up a phylum of microscopic, pseudocoelomate animals. ... Orders Cyclorhagida Homalorhagida Kinorhyncha (Gr. ... This article needs to be cleaned up to conform to a higher standard of quality. ... The gastrotrichs (from Greek gaster stomach and thrix hair) are a phylum of microscopic animals, found in fresh water and marine environments. ... Loricifera is a small phylum of marine sediment-dwelling animals with about a dozen known species. ... Priapulida (priapulid worms, or penis worms) are a phylum of marine worms with an extensible spiny proboscis. ... Classes Archiacanthocephala Palaeacanthocephala Eoacanthocephala The Acanthocephala (gr. ... The term aschelminth is used for any member of about ten different invertebrate phyla. ... Orders Barentsiidae (Urnatellidae) Loxokalypodidae Loxosomatidae Pedicellinidae Entoprocta (Gr. ...

No coelom

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.


Human body cavities

It has been suggested that this section be split into a new article. (Discuss)

The human body consists of the following cavities: Image File history File links Splitsection. ...

Human body cavities and membranes
Name of cavity Principal contents Membranous lining
Dorsal body cavity Cranial cavity Brain Meninges
Vertebral canal Spinal cord Meninges
Ventral body cavity Thoracic cavity Pleura cavities Lungs Pleurae
Pericardial cavity Heart Pericardium
Abdominopelvic cavity Abdominal cavity Digestive organs, spleen, kidneys Peritoneum
Pelvic cavity Bladder, reproductive organs Peritoneum

This page meets Wikipedias criteria for speedy deletion. ... A hippopotamus skull A skull, or cranium, is a bony structure of Craniates which serves as the general framework for a head. ... Brains has several meanings. ... The spinal cord is a part of the vertebrate nervous system that is enclosed in and protected by the vertebral column (it passes through the spinal canal). ... Cross-section through cervical spinal cord. ... The thoracic cavity is the chamber of the human body (and other animal bodies) that is enclosed by the ribcage and the diaphragm. ... The lungs flank the heart and great vessels in the chest cavity. ... The heart and lungs (from an older edition of Grays Anatomy) The heart (Latin cor) is a hollow, muscular organ that pumps blood through the blood vessels by repeated, rhythmic contractions. ... The abdominal cavity is the cavity of the human body (and other animal bodies) that holds the bulk of the viscera and which is located below (or posterior to) the thoracic cavity. ... Human kidneys viewed from behind with spine removed The kidneys are bean-shaped excretory organs in vertebrates. ... Transverse section of ureter. ... For the Physics term GUT, please refer to Grand unification theory The gastrointestinal or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and... This page meets Wikipedias criteria for speedy deletion. ... Comparative brain sizes In animals, the brain, or encephalon (Greek for in the head), acts as the control center of the central nervous system. ... The meninges (singular meninx) are the system of membranes that envelop the central nervous system. ... Cross-section through cervical spinal cord. ... The meninges (singular meninx) are the system of membranes that envelop the central nervous system. ... The thoracic cavity is the chamber of the human body (and other animal bodies) that is enclosed by the ribcage and the diaphragm. ... In anatomy, the pleural cavity is the potential space between the lungs and the chest wall. ... The lungs flank the heart and great vessels in the chest cavity. ... In anatomy, the pleural cavity is the potential space between the lungs and the chest wall. ... The pericardium is a double-walled sac that contains the heart and the roots of the great vessels. ... The heart and lungs (from an older edition of Grays Anatomy) The heart (Latin cor) is a hollow, muscular organ that pumps blood through the blood vessels by repeated, rhythmic contractions. ... The pericardium is a double-walled sac that contains the heart and the roots of the great vessels. ... The abdominal cavity is the cavity of the human body (and other animal bodies) that holds the bulk of the viscera and which is located below (or posterior to) the thoracic cavity. ... The gastrointestinal or digestive tract, also referred to as the GI tract or the alimentary canal or the gut, is the system of organs within multicellular animals which takes in food, digests it to extract energy and nutrients, and expels the remaining waste. ... The spleen is a ductless, vertebrate gland that is not necessary for life but is closely associated with the circulatory system, where it functions in the destruction of old red blood cells and removal of other debris from the bloodstream, and also in holding a reservoir of blood. ... Human kidneys viewed from behind with spine removed The kidneys are bean-shaped excretory organs in vertebrates. ... 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. ... A bladder is a pouch or other flexible enclosure with waterproof or gasproof walls. ... A sex organ, or primary sexual characteristic, narrowly defined, is any of those parts of the body (which are not always bodily organs according to the strict definition) which are involved in sexual reproduction and constitute the reproductive system in an complex organism; namely: Male: penis (notably the glans penis... 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. ...

References

  • Biology. Sixth Edition by Solomon, Berg and Martin. ISBN 0-534-39175-3.
  • Evers, Christine A., Lisa Starr. Biology:Concepts and Applications. 6th ed. United States:Thomson, 2006. ISBN 0-534-46224-3.
  • "coelom." The Columbia Electronic Encyclopedia, Sixth Edition. Columbia University Press., 2003. Answers.com 02 . 2006. http://www.answers.com/topic/body-cavity
  • Zoolab
  • Glasgow University Science Museum

External links


  Results from FactBites:
 
pseudocoelom - Encyclopedia.com (174 words)
pseudocoelom A second body cavity (the first being the gut) which occupies a space between the mesoderm of the body wall and the endoderm of the gut.
There are no mesenteries suspending the internal organs and no muscular layers around the gut; thus in no pseudocoelomate animal does muscular peristalsis move food through the alimentary canal.
Kinking is greatest in dorsal bends where the detached ventral muscle bands could slip the farthest across the pseudocoelom from their normal position, thus producing a greater component of force perpendicular to the cuticle.
  More results at FactBites »

 
 

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