Category: Embryology In the developing vertebrate embryo, somites are masses of mesoderm distributed along the two sides of the neural tube and that will eventually become dermis (dermatome), skeletal muscle (myotome), and vertebrae (sclerotome). ... In the developing vertebrate embryo, the somitomeres are loose masses of paraxial mesoderm derived cells that form along each side of the neural tube towards the end of the third gestational week. ... In vertebrate embryonic development, a group of embryonic tissues formed from somites that develop into the vertebrae. ... In vertebrate embryonic development, a group of tissues formed from somites that develop into the body wall muscle. ... The cutis plate is the dorsal portion of the paraxial mesoderm somite which gives rise to dermis. ... This article is about female reproductive anatomy. ... Allantois is a part of a developing animal embryo. ... The trophoblast (from Greek threphein: to feed) is considered to be the first of all embryonic annexes. ... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... Syncytiotrophoblasts are cells found in the placenta of human embryos. ... The gestational sac is the only available intrauterine structure that can be used to determine if an intrauterine pregnancy (IUP) exists, until the embryo is identified. ... The yolk sac is the first element seen in the gestational sac during pregnancy, usually at 5 weeks gestation. ... The placenta is an ephemeral (temporary) organ present in female placental vertebrates during gestation (pregnancy), but a placenta has evolved independently also in other animals as well, for instance scorpions and velvet worms. ... In placental mammals, the umbilical cord is a tube that connects a developing embryo or fetus to the placenta. ... Umbilical arteries carry deoxygenated blood from the fetus to the placenta in the umbilical cord. ... Fetal circulation; the umbilical vein is the large, red vessel at the far left The umbilical vein is a blood vessel present during fetal development that carries oxygenated blood from the placenta to the growing fetus. ... Whartons jelly is a gelatinous substance within the umbilical cord. ... A drawing of the amniotic sac from Grays Anatomy. ... For the alien race in Stephen Donaldsons The Gap Cycle, see Amnion (Gap Cycle). ... For the entertainment company see Chorion (company) The chorion surrounds the embryo and other membranes. ... Decidua is the term for the uterine lining (endometrium) during a pregnancy. ... Before the fertilized ovum reaches the uterus, the mucous membrane of the body of the uterus undergoes important changes and is then known as the decidua. ... The trophoblast proliferates rapidly and forms a network of branching processes which cover the entire ovum and invade and destroy the maternal tissues and open into the maternal bloodvessels, with the result that the spaces in the trophoblastic network are filled with maternal blood; these spaces communicate freely with one... Chorionic villi are villi that sprout from the chorion, in order to give a maximum area of contact with the maternal blood. ... In the development of vertebrate animals, the branchial arches (or pharyngeal arches) develop during the fourth and fifth week in utero as a series of mesodermal outpouchings on the left and right sides of the developing pharynx. ... It has been suggested that this article or section be merged into branchial arch. ... The cartilaginous bar of the mandibular arch is formed by what are known as Meckel’s cartilages (right and left) ; above this the incus is developed. ... The hyoid arch (or second branchial arch) assists in forming the side and front of the neck. ... Pharyngeal or branchial pouches form on the endodermal side between the branchial arches, and pharyngeal grooves (or clefts) form from the lateral ectodermal surface of the neck region to separate the arches. ... The mandibular and hyoid arches grow more rapidly than those behind them, with the result that the latter become, to a certain extent, telescoped within the former, and a deep depression, the cervical sinus, is formed on either side of the neck. ... During the third week there appears, immediately behind the ventral ends of the two halves of the mandibular arch, a rounded swelling named the tuberculum impar, which was described by His as undergoing enlargement to form the buccal part of the tongue. ... Pattern of the branchial arches. ... During the third week two areas of thickened ectoderm, the olfactory areas, appear immediately under the fore-brain in the anterior wall of the stomodeum, one on either side of a region termed the frontonasal prominence (or process). ... By the upgrowth of the surrounding parts the olfactory areas are converted into pits, the olfactory pits, which indent the fronto-nasal process and divide it into a medial and two lateral nasal processes. ... By the upgrowth of the surrounding parts the olfactory areas are converted into pits, the olfactory pits, which indent the fronto-nasal process and divide it into a medial and two lateral nasal processes (or nasal prominences[1] The terms nasolateral and nasomedial are also used. ... The rounded lateral angles of the medial process constitute the globular processes. ... By the fusion of the maxillary and nasal processes in the roof of the stomodeum the primitive palate (or primary palate[1]) is formed, and the olfactory pits extend backward above it. ... An Introduction to Histogenesis Histogenesis is defined as the formation of tissues and organs from undifferentiated cells (Encarta Dictionary). ... Organogenesis is a stage of animal development where the ectoderm, endoderm, and mesoderm are formed. ... A gland is an organ in an animals body that synthesizes a substance for release such as hormones, often into the bloodstream (endocrine gland) or into cavities inside the body or its outer surface (exocrine gland). ... The thyroglossal duct is an embryological anatomical structure which forms the connection between the initial area of development of the thyroid gland and its final position. ... The vertebrate limb arises out of a general morphogenetic area called a limb field. ... In embryology, the limb bud is a structure formed by the developing limb, derived from lateral plate mesoderm[citation needed]. It is intimately related with the apical ectodermal ridge, which secretes factors inducing the initial differentiation of the limb bud. ... The Apical Ectodermal Ridge (AER) is a critical component in vertebrate limb development. ... Radiograph of lower right (from left to right) third, second, and first molars in different stages of development. ... The dental papilla is a condensation of ectomesenchymal cells called odontoblasts, seen in histologic sections of a developing tooth. ... An odontoblast is a biological cell of neural crest origin that is part of the outer surface of the dental pulp, and whose biological function is dentinogenesis, which is the creation of dentin, the substance under the tooth enamel. ... Ameloblast is the blast that synthezises enamel proteins that later mineralise to form enamel on teeth. ...