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Encyclopedia > Germ layer
Organs derived from each germ layer. Image from NCBI.
Organs derived from each germ layer. Image from NCBI.

A 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 agnotozoans) produce two or three primary tissue layers (sometimes called primary germ layers). Animals with radial symmetry, like cnidarians, produce two called ectoderm and endoderm, making them diploblastic. Animals with bilateral symmetry produce a third layer in-between called mesoderm, making them triploblastic. Germ layers will eventually give rise to all of an animal’s tissues and organs through a process called organogenesis. Image File history File links Cell_differentiation. ... Image File history File links Cell_differentiation. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell. Cells in culture, stained for keratin (red) and DNA (green). ... Embryogenesis is the process by which the embryo is formed and develops. ... Classes and Clades See below Male and female Superb Fairy-wren Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns. ... Animalia redirects here. ... Classes Calcarea Hexactinellida Demospongiae The sponges or poriferans (from Latin porus pore and ferre to bear) are animals of the phylum Porifera. ... subgroups Ctenophora Cnidaria Bilateria Eumetazoa is a clade comprising all major animal groups except sponges. ... The elaborate patterns on the wings of butterflies are one example of biological symmetry. ... Classes Anthozoa - Corals and sea anemones Scyphozoa - Jellyfish Staurozoa - Stalked jellyfish Cubozoa - Sea wasps or box jellyfish Polypodiozoa Hydrozoa - Hydroids, hydra-like animals Cnidaria[1] (IPA: [2]) is a phylum containing some 11,000 species of relatively simple animals found exclusively in aquatic, mostly marine, environments. ... The ectoderm is outermost of the three germ layers of the developing embryo, the other two being the mesoderm and the endoderm. ... The endoderm, sometimes refered to as entoderm, is one of the three germ layers of the developing embryo, the other two being the ectoderm and the mesoderm. ... Diploblastic is a condition of the ovum in which there are two primary germinal layers: the ectoderm and endoderm. ... The elaborate patterns on the wings of butterflies are one example of biological symmetry. ... The mesoderm is one of the three germ layers in the early developing embryo, the other two layers being the ectoderm and the endoderm. ... Triploblastic is a condition of the ovum in which there are three primary germinal layers: the ectoderm, mesoderm, and endoderm. ... Biological tissue is a collection of interconnected cells that perform a similar function within an organism. ... In biology, an organ (Latin: organum, instrument, tool) is a group of tissues that perform a specific function or group of functions. ... Organogenesis is a stage of animal development where the ectoderm, endoderm, and mesoderm are formed. ...

Contents

Germ layers

Gastrulation of a diploblast: The formation of germ layers from a (1) blastula to a (2) gastrula. Some of the ectoderm cells (orange) move inward forming the endoderm (red).
Gastrulation of a diploblast: The formation of germ layers from a (1) blastula to a (2) gastrula. Some of the ectoderm cells (orange) move inward forming the endoderm (red).

Caspar Friedrich Wolff observed organization of the early embryo in leaf-like layers. Later, Heinz Christian Pander discovered germ layers while studying chick embryos. Download high resolution version (801x486, 94 KB) Author Pidalka44. ... Download high resolution version (801x486, 94 KB) Author Pidalka44. ... Caspar Friedrich Wolff (January 18, 1734 _ February 22, 1794) was a significant German anatomist. ... Pander studied the chick embryo and discovered the germ layers (i. ...


Among animals, sponges show the simplest organization, having a single germ layer. Although they have differentiated cells (e.g. collar cells), they lack true tissue coordination. Diploblastic animals, Cnidaria and ctenophores, show an increase in complexity, having two germ layers, the endoderm and ectoderm. Diploblastic animals are organized into recognisable tissues. All higher animals (from flatworms to man) are triploblastic, having in addition a mesoderm. Triploblastic animals develop recognisable organs. Animalia redirects here. ... Classes Calcarea Hexactinellida Demospongiae The sponges or poriferans (from Latin porus pore and ferre to bear) are animals of the phylum Porifera. ... Choanocytes (also known as collar cells) are cells that line the interior body walls of sponges that contain a central flagellum surrounded by a collar of microvilli. ... Diploblastic is a condition of the ovum in which there are two primary germinal layers: the ectoderm and endoderm. ... Classes Anthozoa - Corals and sea anemones Scyphozoa - Jellyfish Staurozoa - Stalked jellyfish Cubozoa - Sea wasps or box jellyfish Polypodiozoa Hydrozoa - Hydroids, hydra-like animals Cnidaria[1] (IPA: [2]) is a phylum containing some 11,000 species of relatively simple animals found exclusively in aquatic, mostly marine, environments. ... Classes Tentaculata Nuda Ctenophores are jellyfish-like animals commonly called comb jellies, sea gooseberries, sea walnuts, or Venus girdles. ... The endoderm, sometimes refered to as entoderm, is one of the three germ layers of the developing embryo, the other two being the ectoderm and the mesoderm. ... The ectoderm is outermost of the three germ layers of the developing embryo, the other two being the mesoderm and the endoderm. ... Triploblastic is a condition of the ovum in which there are three primary germinal layers: the ectoderm, mesoderm, and endoderm. ... The mesoderm is one of the three germ layers in the early developing embryo, the other two layers being the ectoderm and the endoderm. ...


Development

Fertilization leads to the formation of a zygote. During the next stage, cleavage, mitotic cell divisions transform the zygote into a tiny ball of cells called a blastula. This early embryonic form undergoes a massive reorganization called gastrulation forming a gastrula with either two or three layers (the germ layers). In all vertebrates, these are the forerunners of all adult tissues and organs. Fertilisation or fertilization (also known as conception, fecundation and syngamy), is fusion of gametes to form a new organism of the same species. ... A zygote (Greek: ζυγωτόν) is a cell that is the result of fertilization. ... In embryology, cleavage is the division of cells in the early embryo. ... Mitosis divides genetic information during cell division. ... Blastulation. ... 1 - blastula, 2 - gastrula; orange - ectoderm, red - endoderm. ... 1 - blastula, 2 - gastrula; orange - ectoderm, red - endoderm. ... Classes and Clades See below Male and female Superb Fairy-wren Vertebrates are members of the subphylum Vertebrata (within the phylum Chordata), specifically, those chordates with backbones or spinal columns. ...


The appearance of the archenteron marks the onset of gastrulation. The archenteron is an indentation that forms early on in a developing blastula. ...


Endoderm

The endoderm produces tissue within the lungs, thyroid, and pancreas.
The endoderm produces tissue within the lungs, thyroid, and pancreas.
Main article: Endoderm

The endoderm is one of the germ layers formed during animal embryogenesis. Cells migrating inward along the archenteron form the inner layer of the gastrula, which develops into the endoderm. Image File history File links Endoderm2. ... Image File history File links Endoderm2. ... The endoderm, sometimes refered to as entoderm, is one of the three germ layers of the developing embryo, the other two being the ectoderm and the mesoderm. ... Respiratory system The lungs flank the heart and great vessels in the chest cavity. ... The pancreas is an organ in the digestive and endocrine system (of vertebrates[2]). It is both exocrine (secreting pancreatic juice containing digestive enzymes) and endocrine (producing several important hormones, including insulin, glucagon, and somatostatin). ... The endoderm, sometimes refered to as entoderm, is one of the three germ layers of the developing embryo, the other two being the ectoderm and the mesoderm. ... The endoderm, sometimes refered to as entoderm, is one of the three germ layers of the developing embryo, the other two being the ectoderm and the mesoderm. ...


The endoderm consists at first of flattened cells, which subsequently become columnar. It forms the epithelial lining of the whole of the digestive tube excepting part of the mouth and pharynx and the terminal part of the rectum (which are lined by involutions of the ectoderm). The lining cells of all the glands which open into the digestive tube, including those of the liver and pancreas, the epithelium of the auditory tube and tympanic cavity, of the trachea, bronchi, and air cells of the lungs, of the urinary bladder and part of the urethra, and that which lines the follicles of the thyroid gland and thymus are also formed by this layer.


The endoderm forms: stomach, colon, liver, pancreas, urinary bladder; epithelial parts of trachea, lungs, pharynx, thyroid, intestine. The endoderm, sometimes refered to as entoderm, is one of the three germ layers of the developing embryo, the other two being the ectoderm and the mesoderm. ...


Mesoderm

The mesoderm aids in the production of cardiac muscle, skeletal muscle, smooth muscle, tissues within the kidneys, and red blood cells.
The mesoderm aids in the production of cardiac muscle, skeletal muscle, smooth muscle, tissues within the kidneys, and red blood cells.
Main article: Mesoderm

The mesoderm germ layer forms in the embryos of animals more complex than cnidarians, making them triploblastic. During gastrulation, some of the cells migrating inward contribute to the mesoderm, an additional layer between the endoderm and the ectoderm. Image File history File links Mesoderm. ... Image File history File links Mesoderm. ... The mesoderm is one of the three germ layers in the early developing embryo, the other two layers being the ectoderm and the endoderm. ... Cardiac muscle is a type of involuntary mononucleated, or uninucleated, striated muscle found exclusively within the heart. ... A top-down view of skeletal muscle Skeletal muscle is a type of striated muscle, attached to the skeleton. ... Cultured Smooth muscle of the aorta. ... It has been suggested that Renal anomalies and Renal plasma threshold be merged into this article or section. ... Human red blood cells Red blood cells are the most common type of blood cell and the vertebrate bodys principal means of delivering oxygen from the lungs or gills to body tissues via the blood. ... The mesoderm is one of the three germ layers in the early developing embryo, the other two layers being the ectoderm and the endoderm. ... It has been suggested that embryology be merged into this article or section. ... Animalia redirects here. ... Classes Anthozoa - Corals and sea anemones Scyphozoa - Jellyfish Staurozoa - Stalked jellyfish Cubozoa - Sea wasps or box jellyfish Polypodiozoa Hydrozoa - Hydroids, hydra-like animals Cnidaria[1] (IPA: [2]) is a phylum containing some 11,000 species of relatively simple animals found exclusively in aquatic, mostly marine, environments. ... Triploblastic is a condition of the ovum in which there are three primary germinal layers: the ectoderm, mesoderm, and endoderm. ... 1 - blastula, 2 - gastrula; orange - ectoderm, red - endoderm. ... The mesoderm is one of the three germ layers in the early developing embryo, the other two layers being the ectoderm and the endoderm. ... The ectoderm is outermost of the three germ layers of the developing embryo, the other two being the mesoderm and the endoderm. ...


This key innovation evolved hundreds of millions of years ago and led to the evolution of nearly all large, complex animals. The formation of a mesoderm led to the formation of a coelom. Organs formed inside a coelom can freely move, grow, and develop independently of the body wall while fluid cushions and protects them from shocks. By the broadest definition, a body cavity is any fluid filled space in a multicellular organism. ...


The mesoderm forms: skeletal muscle, skeleton, dermis of skin, connective tissue, urogenital system, heart, blood (lymph cells), and spleen. The mesoderm is one of the three germ layers in the early developing embryo, the other two layers being the ectoderm and the endoderm. ...


Ectoderm

The ectoderm produces tissues within the epidermis and aids in the formation of neurons within the brain, and melanocytes.
The ectoderm produces tissues within the epidermis and aids in the formation of neurons within the brain, and melanocytes.
Main article: Ectoderm

The ectoderm is the start of a tissue that covers the body surfaces. It emerges first and forms from the outermost of the germ layers. Image File history File links Ectoderm. ... Image File history File links Ectoderm. ... The ectoderm is outermost of the three germ layers of the developing embryo, the other two being the mesoderm and the endoderm. ... It has been suggested that this article or section be merged with skin. ... Drawing by Santiago Ramón y Cajal of neurons in the pigeon cerebellum. ... Melanocytes are cells located in the bottom layer of the skins epidermis. ... The ectoderm is outermost of the three germ layers of the developing embryo, the other two being the mesoderm and the endoderm. ...


The ectoderm forms: Central nervous system, retina and lens, cranial and sensory, ganglia and nerves, pigment cells, head connective tissue, epidermis, hair, mammary glands. The ectoderm is outermost of the three germ layers of the developing embryo, the other two being the mesoderm and the endoderm. ...


Neural crest

Due to the great importance of the neural crest it has been referred to as the fourth germ layer. The neural crest, a component of the ectoderm, is one of several ridgelike clusters of cells found on either side of the neural tube in vertebrate embryos. ...


References

  • Evers, Christine A., Lisa Starr. Biology:Concepts and Applications. 6th ed. United States:Thomson, 2006. ISBN 0-534-46224-3.

See also


  Results from FactBites:
 
ScienceDaily: Germ layer (1585 words)
A germ layer is a collection of cells, formed during animal embryogenesis.
Germ layer -- A germ layer is a collection of cells, formed during animal embryogenesis.
Epithelium -- In zootomy, epithelium is a tissue composed of a layer of cells.
Germ layer Summary (2696 words)
The outer cell layer of an amphibian gastrula and the superficial cell layer of a bird, reptile and mammalian primitive streak stage is referred to as ectoderm.
Mesoderm is one of the three primary germ layers of a vertebrate embryo.
The superficial layer is known as ectoderm, the interior layer is endoderm, and the middle germ layer is known as mesoderm.
  More results at FactBites »

 
 

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