Representatives of the Type Coelenterates are multicellular animals that have ray (radial) symmetry.

Their body is made up of two layers of cells- external ( ectoderm) and internal ( endoderm), between which is located mesoglea.

Basically, coelenterates are predators. They have intestinal cavity where food is digested. The cavity communicates with the environment through mouth. There are no other openings (undigested residues are thrown out through the mouth).

Structural diagram of intestinal cavities (on the example of freshwater hydra)

Pay attention!

ectoderm formed epithelial-muscular, stinging, nervous, sexual and intermediate (non-specialized) cells.

Endoderm presented digestive-muscular and glandular cells.

Cell Functions

1. Epithelial-muscular (skin-muscular) the cells will perform an integumentary function, and also have muscle processes that provide movement of the intestinal cavity.

2. Stinging cells have a capsule filled with poison that paralyzes the victim (neuroparalytic action). Immersed in a capsule stinging thread. Located on the surface of the cell sensitive hair. When this hair is touched, the stinging thread is thrown out and enters the body of the victim.

Scheme of the structure of the stinging cell

3. Nerve cells have long processes that together form a neural network. Such a nervous system is called diffuse.

The nervous system and the perception of hydra irritation

4. Sex cells provide sexual reproduction of intestinal.

5. Glandular cells produce enzymes that digest food in the intestinal cavity (this intracavitary digestion).

6. Digestive-muscular cells have flagella and prolegs. Flagella move water with food particles, and the resulting pseudopods capture it. Further digestion occurs in the digestive vacuoles (this intracellular digestion).

7. Non-specialized (intermediate) cells are able to transform into any type of cells and provide regeneration (restoration of lost parts) of the intestinal.

Knidocil- sensitive hair of the stinging cell of the coelenterates.

Enzymes- biologically active substances that accelerate the processes taking place in the cell. Digestive enzymes speed up the digestion process.

reproduction

Reproduction of intestinal cavities occurs sexually and asexually.

Asexual reproduction occurs by budding.

In the case of sexual reproduction, a new organism in the larval stage develops from a fertilized egg. Attached to the bottom, the larva turns into a polyp. Polyps either form colonies or bud free-living jellyfish. Here we can talk about the alternation of generations: an attached polyp and a free-living jellyfish.

The value of coelenterates

Representatives of the Intestinal - coral polyps form reefs, and sometimes entire islands - atolls - which represent special ecosystems.

The ectoderm is the outer germ layer from which the skin, or epidermis, and nervous system develop in the early fetal period. That part of the outer germ layer that goes to build the skin epithelium is called the skin ectoderm, and the part that forms the nervous system is called the neuroectoderm.

Ectoderm (from the Greek ektos - outside, outside and derma - skin, layer) - the outer germ layer, the outermost of the cell layers of the embryo in all multicellular animals. The ectoderm initially consists of one closed layer of homogeneous poorly differentiated cells, which, in the course of further differentiation, are divided into groups that differ from each other - various ectodermal rudiments. The cells of each of them, specializing in different directions, give rise to certain tissues.

In the embryos of higher vertebrates and humans, during gastrulation, the primary ectoderm (epiblast) and endoderm are first separated. Only after separation from the epiblast of the material of the middle germ layer, or mesoderm (see), does the outer leaf of the embryo become the ectoderm itself (secondary), which differentiates into skin ectoderm, extra-embryonic ectoderm and neuroectoderm.

The skin ectoderm subsequently forms the skin epithelium, or epidermis, with its tissue derivatives (skin glands, hair, nails, etc.), as well as the epithelium of the vestibule of the oral cavity and the anal rectum. The epithelium of most of the oral cavity, pharynx, esophagus and respiratory tract, also related to the epithelium of the skin type, arises from a special rudiment - the prechordal plate.

From the extraembryonic ectoderm, the integumentary epithelium of the yolk sac (in fish), the serous membrane of the embryo (in reptiles, birds) and the epithelium lining the amnion cavity (in all higher vertebrates) are formed. The trophoblast of mammalian and human embryos is also a part of the extraembryonic ectoderm that separates already during egg cleavage and early specializes.

The neuroectoderm (the rudiment of the nervous system) is represented by the neural plate, ganglionic plate and placodes. The neural plate, which represents the medial portion of the ectoderm on the dorsal side of the embryo, arises under the influence of the chordomesoderm material underlying it during gastrulation. It bends, forming a neural groove, which then, closing its edges, turns into a neural tube - the rudiment of the spinal cord and brain. The latter is immersed under the skin ectoderm, which closes above it. Neural folds - thickened edges of the neural groove - after it is closed into a tube, they are isolated in the form of a ganglionic plate, or neural crest (between the neural tube and the skin ectoderm). The ganglionic plate, segmenting, forms the rudiments of sensitive spinal nodes. Some of its cells, migrating far to the periphery, form the beginnings of sympathetic ganglia and adrenal medulla, or differentiate into pigment cells - melanophores. In the area of ​​the head and neck, part of the cells of the ganglion plate gives rise to ectomesenchyme (see Mesenchyme). Placodes - small islands of neuroectoderm as part of the skin ectoderm - are the rudiments of a number of cranial nerve nodes, the membranous labyrinth of the inner ear and the lens of the eye.

The epithelium and glands that develop from the skin and extraembryonic ectoderm, as well as the prechordal plate, are of the epidermal tissue type in terms of their properties. Tissue derivatives of the neuroectoderm (neurons, neuroglia, primary sensory cells, epithelium of the ependymal group) constitute the glioneural tissue type. See also germ layers.

ECTODERM [ectoderm(LNE); Greek ektos outside, outside + derma skin] - the outer germ layer of the body of the embryo, formed during gastrulation.

In the embryos of all multicellular animals, the primary ectoderm, or epiblast, occurs in the first phase of gastrulation (see). In higher vertebrates, including humans, the ectoderm itself, or secondary ectoderm, becomes that part of the epiblast that remains outside after the isolation of the mesoderm and the release of cellular material, giving rise to the notochord in the second phase of gastrulation.

The secondary ectoderm already during gastrulation is divided into three parts: neuroectoderm (or neural rudiment), represented by the neural plate, skin ectoderm and non-embryonic ectoderm.

The neural plate flexes to form the neural groove. The edges of the groove (neural folds) close, forming the neural tube, which is the rudiment of the spinal cord and brain. When the neural tube is closed, the so-called neural crest is formed, which forms two ganglionic plates on the sides of the neural tube. The tissue derivatives of the neural crest are neurons of sensory and autonomic (sympathetic) nodes, all peripheral neuroglia, chromatophores (pigment cells), and chromaffin tissue of the adrenal glands. Part of the mesenchyme also arises from the cells of the neural crest (see) - the ectomesenchyme. The composition of the neuroectoderm also includes small isolated islands of the neural rudiment localized in the skin ectoderm of the head (the so-called placodes). These include the rudiments of sensitive nodes of the cranial (cranial, T.) nerves, including the statoacoustic, or "auditory", placode - the rudiment of the membranous labyrinth of the inner ear and associated nodes of the vestibulocochlear nerve, as well as the lens placode - the area ectoderm, which forms the rudiment of the lens.

The skin ectoderm is the rudiment of the epithelium of the skin (epidermis) and its derivatives - sebaceous and sweat glands, hair, nails, and in mammals also claws, hooves, horns, in birds - beak, feathers. In the region of the oral and anal bays of the embryo, the ectoderm invaginates towards the anterior and posterior ends of the midgut. These invaginations break into the cavity of the midgut, forming, respectively, the anterior and hindgut. The lining of the foregut, arising from the material of the ectoderm and the prechordal plate, gives rise to the development of the epithelium of the oral cavity, larynx, trachea, bronchi, thymus, thyroid, parathyroid glands, anterior pituitary gland, pharynx, esophagus. From the ectodermal lining of the posterior intestine, the epithelium of the bladder, ureter, and part of the rectum develops.

The extra-embryonic ectoderm, which is a continuation of the skin ectoderm, is part of the temporary germinal organs, including the germinal membranes, and forms the outer epithelium of the serous membrane, the amnion epithelium, in the embryos of higher vertebrates (see Embryo, Fetal membranes). In mammals and humans, a part of the extra-embryonic ectoderm already at the beginning of the crushing of a fertilized egg is isolated in the form of a trophoblast (see).

Bibliography: Klishov A. A. Histogenesis and tissue regeneration, L., 1984; Knorre A. G. Embryonic histogenesis, L., 1971; Stanek I. Human embryology, trans. from Slovak, Bratislava, 1977.

A. G. Knorre, A. A. Klipov.

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The meaning of the word ectoderm

ectoderm in the crossword dictionary

Dictionary of medical terms

ectoderm (ectoderm, LNE; ecto- + Greek derma skin)

outer germ layer of a three-layer embryo; E.'s derivatives are the epidermis, the nervous system, and, to a large extent, the sense organs.

Encyclopedic Dictionary, 1998

ectoderm

ECTODERM (from ecto... and dermis)

outer germ layer of multicellular animals. From the ectoderm, the skin epithelium, nervous system, sensory organs, anterior and posterior intestines are formed. Wed Endoderm, Mesoderm.

The outer layer of the body wall in coelenterates.

ectoderm

E., or the outer germ layer, the outer layer of the embryo of multicellular animal organisms at the gastrula stage. From E. in the process of development of the embryo, integuments, the nervous system, sensory organs, the anterior and posterior sections of the digestive system, external gills, and also ectomesenchyme are formed. In deuterostomes, all derivatives of E. are formed as a result of induction influences on it by the chordomesoderm, endoderm, and their derivatives.

The outer wall of the body of intestinal animals, consisting of one layer of cells: epithelial, epithelial-muscular, intermediate (interstitial), sensitive (nerve), and also stinging.

Wikipedia

ectoderm

ectoderm- the outer germ layer of the embryo in the early stages of development. There is also a middle germ layer - the mesoderm and the germ layer furthest from the ectoderm - endoderm. In the embryo, it is formed first and is formed from the outer layer of germ cells. The ectoderm forms the nervous system (in vertebrates: spinal cord, peripheral nerves, and brain), tooth enamel, and epidermis. It also forms the sense organs, the epithelium of the anterior and posterior sections of the digestive system.

In vertebrates, the ectoderm consists of three parts: the outer ectoderm, the neural crest, and the neural tube. The neural crest and neural tube are also known as the neuroectoderm. Formed at the gastrula stage.

Examples of the use of the word ectoderm in the literature.

Beatrice-Joanna could no longer think of any other obligation than her debt to this one inch of protest, weighing thirty-something grains, whose cells were continually dividing and multiplying - ectoderm, mesoderm, endoderm - protesting, protesting and protesting again.

In these complex organisms, two membranes are distinguished - the endoderm and ectoderm, slightly different from one another, one of them serves to form the digestive sac, the other is the outer shell of the body.

The skin relief is formed at the 9-12th week of intrauterine development from ectoderm- the same embryonic layer from which the central nervous system develops.

ectoderm- the outer germ layer, from which the skin epithelium, nervous system, sensory organs, anterior and posterior intestines are formed.

The doctrine of germ layers, one of the main generalizations in embryology, has played a large role in the history of biology.

In 2000, Canadian embryologist Brian Keith Hall proposed that the neural crest be considered nothing more than a separate fourth germ layer. This interpretation quickly spread in the scientific literature.

In all animals, the same organs are obtained from the same germ layer. The ectoderm gives the outer coverings and the nervous system. Most of the digestive tract and digestive glands are formed from the endoderm (in vertebrates, the liver, pancreas, and lungs). The mesoderm forms the rest of the organs: muscles, lining of the secondary body cavity, organs of the circulatory, excretory and reproductive systems, in vertebrates and echinoderms - the internal skeleton. (It must be borne in mind that most of the organs of an adult animal include tissues originating from two or all three germ layers.) A very important conclusion follows from this: in all animals, the main organ systems have a common origin, and they can be compared. For example, the central nervous system has a common origin in the sense that in evolution it originates from the subcutaneous nerve plexus, similar to the nervous network of the hydra, and in ontogeny from the outer germ layer.

germ layers (lat. embryonic folia), germ layers, layers of the body of the embryo of multicellular animals, formed during gastrulation and giving rise to various organs and tissues. Most organisms have three germ layers:

• outer - ectoderm,
• internal - endoderm,
• middle - mesoderm.

Derivatives of the ectoderm perform mainly integumentary and sensory functions, derivatives of the endoderm - the functions of nutrition and respiration, and derivatives of the mesoderm - connections between parts of the embryo, motor, support and trophic functions.

The same germ layer in representatives of different classes of vertebrates has the same properties, i.e. germ layers are with homologous formations and their presence confirms the position of the unity of the origin of the animal world. Germ layers are formed in embryos of all major classes of vertebrates, i.e. are universally distributed.

The germ layer is a layer of cells that occupies a certain position. But it cannot be considered only from topographic positions. The germ layer is a collection of cells that have certain development trends. A clearly defined, albeit rather wide, range of developmental potentials is finally determined (determined) by the end of gastrulation. Thus, each germ layer develops in a given direction, takes participation in the emergence of the rudiments of certain organs.

Throughout the animal kingdom, individual organs and tissues originate from the same germ layer. From the ectoderm, the neural tube and integumentary epithelium are formed, from the endoderm - the intestinal epithelium, from the mesoderm - muscle and connective tissue, the epithelium of the kidneys, gonads, and serous cavities. From the mesoderm and the cranial part of the ectoderm cells are evicted, which fill the space between the sheets and form the mesenchyme. Mesenchymal cells form syncytium: they are connected to each other by cytoplasmic processes. The mesenchyme forms the connective tissue.

Each individual germ layer is not an autonomous formation, it is part of the whole. The germ layers are able to differentiate only by interacting with each other and being under the influence of the integrating influences of the embryo as a whole. A good illustration of such interaction and mutual influence are experiments on early amphibian gastrula, according to which the cellular material of the ecto-, ento- and mesoderm can be forced to radically change the path of its development, to participate in the formation of organs that are completely uncharacteristic of this leaf. This suggests that, at the beginning of gastrulation, the fate of the cellular material of each germ layer, strictly speaking, is not yet predetermined. The development and differentiation of each leaf, their organogenetic specificity, is due to the mutual influence of the parts of the whole embryo and is possible only with normal integration.