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Origin of mesoderm

Mesoderm - Embryolog

  1. Splanchnic Mesoderm Extra-embryonic Mesoderm. The origin of extra-embryonic mesoderm (EEM) has been extensively discussed in the literature. This mesoderm lies outside the embryo, associated with fetal membrane and placenta development. This mesoderm formed at gastrulation along with the embryonic mesoderm from the proximal side of the primitive streak. A recent study in mouse, has shown that the primitive streak absence and excessive epiblast Nodal activity in pre-gastrulation stage, but.
  2. al layers that appears in the third week of embryonic development. It is formed through a process called gastrulation. There are three important components, the paraxial mesoderm, the intermediate mesoderm and the lateral plate mesoderm
  3. ORIGIN OF THE MESODERM. By CHARLES SEDGWICK MINOT. See all Hide authors and affiliations. Science 28 Dec 1883: Vol. ns-2, Issue 47, pp. 815-818 DOI: 10.1126/science.ns-2.47.815 . Article; Info & Metrics; eLetters; PDF; This is a PDF-only article. The first page of the PDF of this article appears.

Descriptive studies of phoronid development have concluded that the mesoderm of these animals originates from the endoderm during gastrulation. This interpretation has been tested by labeling one blastomere of 4- through 16-cell embryos and examining the position and germ layers occupied by the labeled clones of cells in the larva mesoderm (n.) middle germinal layer of the three-layered embryo of a metazoic animal, 1858, from French mésoderme or German Mesoderm, literally middle skin, coined by German physician Robert Remak (1815-1865) from meso- middle + Greek derma skin (see -derm ). Related: Mesodermal; mesodermic The evolutionary origin of the inner germ layers, endoderm and mesoderm, and their relationship have been a matter of debate for decades. In this review we summarize the major modes of endoderm and..

Mesoderm - Wikipedi

In Nemertodermatida as well as the Acoela, myocytes are subepithelial fiber-type muscle cells and appear to originate from the gastrodermal epithelium by emigration of single cells. Other mesodermal cells in the acoels are the peripheral parenchyma (connective tissue) and tunica cells of the gonads, and these also arise from the gastrodermis We reviewed extensive data in experimental animals to define the origin of the human extraembryonic mesoderm. The extraembryonic mesoderm in humans is important component of the CVS culture preparation. Previously, the extraembryonic mesoderm was thought to originate in the cytotrophoblast or primitive streak Mesoderm, the middle of the three germ layers, or masses of cells (lying between the ectoderm and endoderm), which appears early in the development of an animal embryo

ORIGIN OF THE MESODERM Scienc

  1. The origin of the intermediate mesoderm (IM). During mammalian gastrulation, cells of the epiblast migrate from a lateral to a medial position then ingress through the primitive streak, a furrow stretching from the node or organizer to the posterior of the epiblast (A, B)
  2. (2002) Freeman, Martindale. Developmental Biology. Descriptive studies of phoronid development have concluded that the mesoderm of these animals originates from the endoderm during gastrulation. This interpretation has been tested by labeling one blastomere of 4- through 16-cell embryos and exami..
  3. Origin of the Mesoderm is an article from Science, Volume 2. View more articles from Science.View this article on JSTOR.View this article's JSTOR..
  4. Mesoderm is the middle of the three embryonic germ layers discovered and defined in the 19th century. Major phylogenetic classifications are based on the theory and evidence that the mesoderm is the most recently evolved germ layer
  5. It is suggested that this endodermal meshwork develops as the result of interstitial implantation in the human embryo. A small secondary yolk sac develops in 12- to 13-day human and macaque embryos as the result of pinching off of a portion of the larger primary yolk sac

Toggle menu. Search Search. Institution: BIN mesoderm: [ mez´o-derm ] the middle of the three primary germ layers of the embryo, lying between the ectoderm and entoderm; from it are derived the connective tissue, bone, cartilage, muscle, blood and blood vessels, lymphatics, lymphoid organs, notochord, pleura, pericardium, peritoneum, kidneys, and gonads. adj., adj mesoder´mal,. The view that NCCs contribute to skeletal elements and CT, while CPM gives rise to musculature during pharyngeal development has been challenged by evidence for a mesodermal origin of components of the pharyngeal skeleton and CT in amniotes (Noden, 1988; Tabler et al., 2017; Heude et al., 2018).In these studies, however, the lateral mesoderm (mesoderm adjacent to the otic vesicle and the first. The term mesoderm was introduced into English by Huxley in 1871, and ectoderm and endoderm by Lankester in 1873 Origin of extraembryonic mesoderm in experimental animals: relevance to chorionic mosaicism in humans. Bianchi DW , Wilkins-Haug LE , Enders AC , Hay ED Am J Med Genet , 46(5):542-550, 01 Jun 199

The origin of mesoderm in phoronids

PubMe mesoderm gives rise to the true mesenchyme, from which more mature fibroblasts develop, along with connective tissue, bones, cartilage, and blood and lymphatic circulatory systems. Endothelial cells, adipocytes, and pericytes share a mesodermal origin with fibroblasts, and the process of EndMT has been reported in cardiovascular development.1 About Press Copyright Contact us Creators Advertise Developers Terms Privacy Policy & Safety How YouTube works Test new features Press Copyright Contact us Creators. Mesoderm definition, the middle germ layer of a metazoan embryo. See more

The specific characteristics of the SMC in intimal thickening in atherosclerosis have put several investigators on an interesting conceptual course of allowing these cells to be monoclonal in origin, deriving possibly from a single source. 55 The origin of such a stem cell could in principle reside in both mesoderm and mesectoderm, ie, the. Types of tissues . The human tissue is classified into four basic categories: epithelial tissue, connective tissue, muscle tissue, and nervous tissue. These all types of tissues derived from embryonic tissue (ectoderm, mesoderm, endoderm) and sometimes they vary according to species ORIGIN OF THE MESODERVI. TiHE origin and composition of the mesoderm has been the subject of perhaps more discus-sion than any other single point in the whole raiige of embryology. Observers have given the most conflicting statements, for the most part due to incomplete observations; but now we are at last in a position to eliminate man

The origin of mesoderm in phoronids. Freeman G(1), Martindale MQ. Collaborators: Martindale MQ(2). Author information: (1)Friday Harbor Laboratories, University of Washington. Descriptive studies of phoronid development have concluded that the mesoderm of these animals originates from the endoderm during gastrulation The in situ origin of the pre-oral mesoderm, the complete intersegmentai separation of all but the terminal somites and the occurrence of well developed coelomic sacs in the protocephalon are to be regarded as primitive features in a holometabolan, indicating exopterygote affinities

The endoderm from a diverse perspective | Development

mesoderm Origin and meaning of mesoderm by Online

Descriptive studies of phoronid development have concluded that the mesoderm of these animals originates from the endoderm during gastrulation. This interpretation has been tested by labeling one blastomere of 4- through 16-cell embryos and examining the position and germ layers occupied by the labeled clones of cells in the larva. No 2 injections gave rise to identical clones of cells. accepted, the origin of the mesoderm in the bud has been a point of contention. Hepke ('97) in Naids, von Wagner ('oo and 'o6) in Lumbriculus and Abel ('02) in Tubifex and Nais, among others, are of the opinion that the new mesodermal structures both in anterior and in posterior regeneration are of ectodermal origin

Origin and evolution of endoderm and mesoderm Request PD

  1. [Role of the somitic mesoderm in the development of the rib cage of bird embryos. I. Origin of the sternal component and conditions for the development of the ribs (author's transl)] Chevallier A. J Embryol Exp Morphol, 33(2):291-311, 01 Apr 1975 Cited by: 19 articles | PMID: 117684
  2. oglycan structure on differentiation of human embryonic stem cells towards mesoderm and endoderm lineages. Gut endoderm takes flight from the wings of mesoderm. Malignant peritoneal mesothelioma giving rise to multiple intestinal polyps
  3. Origin and differentiation of the yolk sac and extraembryonic mesoderm in presomite human and rhesus monkey embryos † ‡ W. Patrick Luckett , Department of Anatomy, Creighton University, School of Medicine, Omaha, Nebraska 6817

Therefore, cranial mesoderm is central in vertebrate evolution and hence, the origin of cranial mesoderm is a significant question. Whether the non-segmented cranial mesoderm is a novel embryonic tissue similar to neural crest Footnote 1 * and placodes* [ 5 , 136 , 137 ] or emerged from anterior somites of chordate ancestor that secondarily. The extraembryonic mesoderm in humans is an important component of the CVS culture preparation. Previously, the extraembryonic mesoderm was thought to originate in the cytotrophoblast or primitive streak. More recent evidence supports its origin from the yolk sac, which does not always correlate with the fetal karyotype

Taken together, our results clearly demonstrate a cranial mesoderm origin of striated muscle of the esophagus that is located in the trunk. In a previous study using Z/AP reporter mice, Kaede lineage tracing, and pax3b morpholinos in zebrafish, the ESM was reported to be a derivative of Pax3-derived migratory somitic progenitor A further reason to revisit the mesodermal origin of SMC is the evidence that has turned up from in vivo experiments in which it was shown that the first layers of SM α-actin-expressing cells around the endothelial cell-lined tubes transdifferentiate from the endothelium. 17 It should be studied whether this mechanism is specific for the. The phylum Chordata (cephalochordates, tunicates, vertebrates) is defined by the somites, which are a series of segmental blocks that arise in the paraxial mesoderm during early embryogenesis (Fig. 1a) (Holland et al. 2015; Onai et al. 2015b); in amphioxus, somites span from anterior to posterior, and in vertebrates, somites develop posterior to the otic vesicles and persist into the tail. Somatopleuric mesoderm forms the parietal layer of these cavities (i.e., parietal pericardium, perietal layer of pleura and parietal peritoneum) and splanchnopleuric mesoderm forms the visceral layer of these cavities. Paraxial mesoderm differentiates into somites. By the end of 20th day, the first pair of somites have formed in neck region

Significance of Muscle Cells for the Origin of Mesoderm in

Theories of origin and evolution of coelom. Schizocoel theory: According to this theory, the coelomates evolved from an ancestral acoelomate like flatworms by hollowing out of the parenchymal cells of the mesenchyme. Some of these cells formed the peritoneum. According to this theory, the acoelomate body plan is primary and ancestral to the coelomate plan According to him the mesoderm arises in other Gastropod from two mesoblastic bands. At first each of these bands consists of only a few cells, but later on the number of cells increases, followed by the breaking up of the two bands and subsequent distribution of the mesoderm cells in the cleavage cavity

Developmental Cell Article A Cranial Mesoderm Origin for Esophagus Striated Muscles Swetha Gopalakrishnan,1 Glenda Comai,1 Ramkumar Sambasivan,2 Alexandre Francou,3 Robert G. Kelly,3 and Shahragim Tajbakhsh1,* 1Department of Developmental & Stem Cell Biology, Institut Pasteur, Stem Cells & Development, CNRS URA 2578, 25 Rue du Dr. Roux, 75015 Paris, Franc what is the origin of the mesoderm? epiblasts that do migrate down (ventrally) through the primitive streak during later stages of gastrulation constitute the mesoderm layer; hypoblasts can also become extraembryonic mesoderm. what are the 3 types of mesoderm? paraxial, intermediate, and lateral Mesoderm: Definition & Develops Into. Mesoderm = Muscle , skeleton, circulatory system, gonads, and kidneys come from the mesoderm layer. A handy-dandy mnemonic for mesoderm spells out the following: M uscle (skeletal, cardiac, smooth) E ndothelium of our blood vessels. S pleen. O varies and other gonads. D ducts of genital syste Mesodermal gene expression in the acoel Isodiametra pulchra indicates a low number of mesodermal cell types and the endomesodermal origin of the gonads 15 Pages PloS one, 201

Abstract Muscle tissue may have played a central role in the early evolution of mesoderm. The first function of myocytes could have been to control swimming and gliding motion in ciliated vermiform organisms, as it still is in such present-day basal Bilateria as the Nemertodermatida. The only mesodermal cells between epidermis and gastrodermis in Nemertodermatida are myocytes, and conceivably. Lesson on Gastrulation and the Formation of the 3 Germ Layers known as the Ectoderm, Mesoderm and Endoderm. Gastrulation is a process whereby a bilaminar dis..

Muscle tissue may have played a central role in the early evolution of mesoderm. The first function of myocytes could have been to control swimming and gliding motion in ciliated vermiform organisms, as it still is in such present-day basal Bilateria as the Nemertodermatida. The only mesodermal cells between epidermis and gastrodermis in Nemertodermatida are myocytes, and conceivably the. Mesenchyme is a type of animal tissue comprised of loose cells embedded in a mesh of proteins and fluid, called the extracellular matrix. The loose, fluid nature of mesenchyme allows its cells to migrate easily and play a crucial role in the origin and development of morphological structures during the embryonic and fetal stages of animal life. . Mesenchyme directly gives rise to most of the. mesoderm definition,IELTS Words,TOEFL Words,GRE Words,SAT Words,GMAT Words,English asl dictionary online,dictionary for kids,cambridge dictionary,thesaurus dictionary dictionary.englishtest.info is the world's leading online source for English definitions, synonyms, word origins and etymologies, audio pronunciations, example sentences, slang phrases, idioms, word games, legal and medical. Germ Layers. A germ layer is a group of cells in an embryo that interact with each other as the embryo develops and contribute to the formation of all organs and tissues. All animals, except perhaps sponges, form two or three germ layers. The germ layers develop early in embryonic life, through the process of gastrulation Mesoderm definition: the middle germ layer of an animal embryo , giving rise to muscle , blood, bone ,... | Meaning, pronunciation, translations and example

Somites, blocks of mesoderm tissue located on either side of the neural tube in the developing vertebrate embryo, are derived from mesenchymal cells in the presomitic mesoderm (PSM) and are a defining characteristic of vertebrates. In vertebrates, the somite segmental boundary is determined by Notch signalling and the antagonistic relationship of the downstream targets of Notch, Lfng, and. The evolution of the head was one of the key events that marked the transition from invertebrates to vertebrates. With the emergence of structures such as eyes and jaws, vertebrates evolved an active and predatory life style and radiated into diversity of large-bodied animals. These organs are moved by cranial muscles that derive embryologically from head mesoderm (a) Dorsally situated (b) Mesodermal in origin (c) Rod like (d) All of these We're always here. Join our Discord to connect with other students 24/7, any time, night or day Derivatives of NMPs comprise the paraxial mesoderm and the neural tube (NT) at spinal cord levels. Notably, human pluripotent stem cells induced in vitro to generate trunk-like NC progenitors revealed a transient intermediate neural crest (NC)/NMP state expressing both early NC (Msx1/2, Pax3, Zic1/3) and NMP markers (Bra, Sox2, Msgn1) [5,6,7].More recently, using a trunk-specific foxd3.

Mesoderm and Endoderm. What homologous structures develop from the genital tubercle? Head of the penis and Clitoris. What is the germinal origin of the UG sinus, urethra, Urinary bladder, yolk sac, cloaca, and Detneser muscle. Endoderm The origin of the mesoderm in the Mexican axolotl, Ambystoma mexicanum, has been the subject of discussion in the literature for some time. Løvtrup proposed that the mesoderm originated from cells. Nuclei and Nucleoli in Uninjured Individuals.1. The nuclei and nucleoli of the hypodermal cells are small except in the growing tail region. Here they are enlarged, especially in the cells on the v.. Download this stock image: . Text-book of embryology. Embryology. ORIGIN OF THE MESODERM 63 the endoderm cells along the inner and outer edges of the sheet of mesoderm. In early stages and in the anterior part of the embryo this pro- liferation process may alone be in evidence, so that in place of a broad continuous sheet of mesoderm there are found two narrow strips— one (Fig. 38, C, mes. We are proud to announce that we are partnering with scite, a platform for discovering and evaluating scientific articles. Smart Citations show the citation context, the location of the citation in the citing paper, and a classification indicating if the citation provides supporting or disputing evidence

Origin of extraembryonic mesoderm in experimental animals

What's the origin of intermediate mesoderm? - 1467709 By Gary Freeman, Mark Q. Martindale, Boyer, Brooks, Cohen, Emig, Freeman, Freeman, Halanych, Hay-Schmidt, Henry, Hermann, Ikeda, Jacob, Lacalli, Lawrence, Long, Luter. Head mesenchyme (neural crest and/or mesoderm) 1. Blood vessels. 2. Corneal stroma and endothelium. 3. Stroma of choroid, ciliary body, and iris. 4. Ciliary muscle. 5. Sclera. 6. Optic nerve sheath (meninges) 7. Extraocular muscles and fasciae. 8. Remainder of the eyelids (orbicularis oculi muscle, tarsus, orbital septum, etc) 9 The in situ origin of the pre-oral mesoderm, the complete intersegmental separation of all but the terminal somites and the occurrence of well developed coelomic sacs in the protocephalon are to be regarded as primitive features in a holometabolan, indicating exopterygote affinities

The extraembryonic mesoderm in humans is important component of the CVS culture preparation. Previously, the extraembryonic mesoderm was thought to originate in the cytotrophoblast or primitive streak. More recent evidence supports its origin from the yolk sac, which does not always correlate with the fetal karyotype In our study we used genetic lineage tracing to investigate the cellular origin of the throat in the mouse model. We found that cardiopharyngeal mesoderm (CPM), known to give rise to head and heart muscle, makes a major contribution to mammalian pharyngeal structures. Despite the different positions of the heart and throat in the adult, these. Segmented divisions of intermediate mesoderm form tubules, known as nephrotomes. In total, 6-10 pairs of nephrotomes are formed. These tubules join into the pronephric duct, which is a duct that extends from the cervical region to the cloaca (distal end) of the embryo. This early system is non-functional and regresses completely by the end of. Entries with mesoderms mesoderm: mesoderm (English) Origin & history meso- + -derm Noun mesoderm (pl. mesoderms) (embryology) One of the three tissue layers in the embryo of a metazoan animal.Through embryonic coenoblast: Ancient Greek: κοινός‎ (common) + βλαστός‎ (germ).Noun coenoblast (pl. coenoblasts) (zoology) Germinal tissue of Porifera that forms cores o

Mesoderm embryology Britannic

mesoderm origin. A dual origin was also suggested by K€ontges and Lums-den (1996), because the footplate was not populated by grafted quail neural crest. Although the chick-quail tech-nique has been used successfully to trace neural crest cells in many struc-tures (Le Lie`vre and Le Douarin, 1975), the results are limited by the ac Mesoderm definition is - the middle of the three primary germ layers of an embryo that is the source of many bodily tissues and structures (such as bone, muscle, connective tissue, and dermis); broadly : tissue derived from this germ layer

Intermediate Mesoderm - an overview ScienceDirect Topic

Disruption of the mesoderm, retinoic acid signaling, or TBX4 expression in the endoderm will interfere with this process and can cause defects in lung/trachea development. as the respiratory diverticulum grows, longitudinal mesodermal folds called the tracheo-esophageal ridges form that eventually pinch off to separate the trachea from the. Thus, the origin and evolution of the mesoderm have been central to formulating hypotheses of the transition from a relatively simple radially symmetric ancestor to a complex bilaterian. A crucial topic in the different scenarios is the homology of coelomic cavities and how often they originated in animals [3] , [9] , [10] , [11] The key difference between mesoderm and mesenchyme is that mesoderm is one of the three germ layers of bilaterally symmetrical animals while mesenchyme is an undifferentiated tissue found in embryonic true mesoderm.. In diploblastic animals, the body plan is relatively simple with two layers of cells. The two layers are the outer ectoderm and the inner endoderm Which of the following is mesodermal in origin ? (a) Retina (b) Enamel of teeth (c) Heart (d) Liver. cbse; class-12; Share It On Facebook Twitter Email. 1 Answer +1 vote . answered Dec 3, 2018 by aditi (75.7k points) selected Dec 3, 2018 by faiz . Best answer. Correct Option. The evolutionary origin of the inner germ layers, endoderm and mesoderm, and their relationship have been a matter of debate for decades. In this review we summarize the major modes of endoderm and mesoderm formation found in Metazoa and possible evolutionary scenarios to reconstruct the ancestral state

The origin of mesoderm in phoroni preview & related

Jul 24,2021 - our teeth r mesodermal in origin. WHAT IS MESODERMAL? ??? | EduRev Class 9 Question is disucussed on EduRev Study Group by 165 Class 9 Students The origin of reproductive organs They noticed that by day nine of a mouse's embryonic development, a structure called the posterior intermediate mesoderm (PIM) lit up brightly with the marker for a gene critical to the development of gonads, kidneys, and the hormone-producing adrenal glands, which are located adjacent to the kidneys.. Fingerprint Dive into the research topics of 'The origin of mesoderm in the equal-cleaving nemertean worm Cerebratulus lacteus'. Together they form a unique fingerprint. Sort by Weight Alphabeticall Meaning. mẹsodaamu. Synonym. orukọ ẹka-ọrọ. mesoblast Example. By the time segmentation is complete, strong mxp expression is detected in both ectoderm and mesoderm of the maxillary and labial limb buds.. Why is the origin of mesoderm from hypoblast in some groups not regarded as a secondary adaptation?. Endoderm and mesoderm form from the lower layer of cells

The mesoderm grows into skeletal muscles, bones, connective tissues and the heart and forms the kidneys and the dermis of the skin. LifeMap Sciences reveals that the three germ layers start to separate into distinct sections within the first three weeks of embryonic development. A small, spherical mass of cells rapidly forms the ectoderm. Geerts, A. (2004). On the origin of stellate cells : mesodermal, endodermal or neuro-ectodermal ? (Editorial on invitation). Journal of Hepatology, 40(2), 331-334 Mesenchyme ≠ mesoderm: The mesoderm is one of the three germinal layers that differentiates into different tissues. The mesenchyme is embryonic connective tissue that develops from the mesoderm and other germ layers. Fate mapping. A fate map is used to determine the origin of a cell lineage, e.g., a germ layer. The following table provides an. Embryological background. Lateral plate mesoderm found in the neck region, paraxial mesoderm and neural crest cells all contribute to the development and existence of the skull in its entirety.. The bones of the skull are formed in two different ways; intramembranous ossification and endochondral ossification are responsible for creating compact cortical bone or spongy bone Musculature of the axial skeleton, body wall and limbs is derived from somites. These somites and somitomeres undergo a process of epithelization and form a ball of epithelial cells with a small cavity in the center. Cells in the upper region of the somite form the dermatome (giving rise to skin precursor cells) and two muscle-forming areas.

The distribution and differentiation of the germ cells in these experiments are factors which favour the opinion of an origin of the germ cells in the mesoderm, and the presence of an inductive centre in the dorso-caudal entoderm. 10) After the removal of the whole entoderm at the early neurula stage, the larvae show a reduced number of germ. Note that epithelial tissue originates in all three layers, whereas nervous tissue derives primarily from the ectoderm and muscle tissue derives from the mesoderm. Figure 4.1.2 - Embryonic Origin of Tissues and Major Organs: Embryonic germ layers and the resulting primary tissue types formed by each The role of Brachyury and other T‐box genes in the differentiation of mesoderm and endoderm of vertebrates is well established. Recently, homologues of Brachyury have been isolated from an increasing number of diverse organisms ranging from Cnidaria to vertebrates and insects. Comparative expression and function analysis allows the origin of the mesoderm and the evolution of the. Tunicate Note: origin of visceral- somatic dichotomy Visceral = adult Somatic = larval tail origin of need for dorsal nerve cord, notochord Tunicate and larvae Neoteny = keep immature features into adult Paedogenesis = become an adult Earlier in life Adult = can reproduce * Origin and Differentiation of the Yolk Sac and Extraembryonic Mesoderm in Presomite Human and Rhesus Monkey Ehbryos l s 2 W . PATRICK LUCKETT Department of Anatomy, Creighton University, School of Medicine, Omaha, Nebraska 681 7

Origin of the Mesoderm : Minot, Charles Sedgwick : Free

Paired fins are a defining feature of the jawed vertebrate body plan, but their evolutionary origin remains unresolved. Gegenbaur proposed that paired fins evolved as gill arch serial homologues, but this hypothesis is now widely discounted, owing largely to the presumed distinct embryonic origins of these structures from mesoderm and neural crest, respectively mes·o·derm. (mĕz′ə-dûrm′, mĕs′-) n. The middle embryonic germ layer, lying between the ectoderm and the endoderm, from which connective tissue, muscle, bone, and the urogenital and circulatory systems develop. mes′o·der′mal, mes′o·der′mic adj. American Heritage® Dictionary of the English Language, Fifth Edition ORIGIN OF CHORDATES CHORDATE ORIGINS: Members of Phylum CHORDATA have four primary characters, they are- a) A primitive endoskeleton structure called the NOTOCHORD present during the early embryonic life. This rod-like structure composed of a special type of connective tissue which is located along the mid dorsal line where it forms the axis of.

Mesoderm - an overview ScienceDirect Topic

1. Has either a backbone or a notochord (vertebrate) 2. Can either be an ectotherm or an endotherm 3. Chordates - Chordates Chordates A chordate (Phylum Chordata) is an animal that has, for at least some stage of its life, a dorsal, hollow nerve cord; a notochord; pharyngeal. Evolutionary origin. Dickinsonia costata from the Ediacaran biota (c. 635-542 MYA) is one of the earliest animal species known. The first fossils that might In deuterostomes, the mesoderm forms by enterocoelic pouching, through invagination of the endoderm

embryonic ectoderm - meddicMammalian Developmental Biology Portal - LifeMap DiscoveryStem Cell Application Embryonic Origin Tissues StockVariant origin of the middle colic artery from theSomite Musculoskeletal Movie - Embryology