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59-900: NTERA-2 cells exhibit biochemical and developmental properties similar to the cells of the early embryo , and can be used to study the early stages of human neurogenesis . The cells exhibit a high nucleo - cytoplasmic ratio, prominent nucleoli , and the expression of the glycolipid antigen SSEA-3 . They also express nestin and vimentin , which are found in neuroepithelial precursor cells , as well as microtubule-associated proteins expressed in human neuroepithelium . NTERA-2 cells also accumulate cytoplasmic glycogen . NTERA-2 cells differentiate when exposed to retinoic acid and lose expression of SSEA-3. Differentiation produces neurons via asymmetric cell division , and these cells form interconnected axon networks and express tetanus toxin receptors and neurofilament proteins. By 10–14 days of exposure to retinoic acid, NTERA-2 cells begin to take on

118-408: A seed . Other seed components include the endosperm , which is tissue rich in nutrients that will help support the growing plant embryo, and the seed coat, which is a protective outer covering. The first cell division of a zygote is asymmetric , resulting in an embryo with one small cell (the apical cell) and one large cell (the basal cell). The small, apical cell will eventually give rise to most of

177-416: A baby, and the baby is born with umbilical cord attached. In stage three, which begins after the birth of the baby, further contractions expel the placenta , amniotic sac, and the remaining portion of the umbilical cord usually within a few minutes. Enormous changes take place in the newborn's circulation to enable breathing in air. In the uterus, the fetus is dependent on circulation of blood through

236-432: A glistening grey balloon, with a puppy inside, is propelled through the vulva . After further contractions, the sac is expelled and the bitch breaks the membranes, releasing clear fluid and exposing the puppy. The mother chews at the umbilical cord and licks the puppy vigorously, which stimulates it to breathe. If the puppy has not taken its first breath within about six minutes, it is likely to die. Further puppies follow in

295-495: A lung metastasis from a 22-year-old male patient with primary embryonal carcinoma of the testis . The tumor was xenografted onto a mouse, and from this cells were cloned into the NTERA-2 cell line. Embryo An embryo is the initial stage of development for a multicellular organism . In organisms that reproduce sexually , embryonic development is the part of the life cycle that begins just after fertilization of

354-459: A mature animal can trace their origin back to one of these layers. For example, the ectoderm will give rise to the skin epidermis and the nervous system, the mesoderm will give rise to the vascular system, muscles, bone, and connective tissues, and the endoderm will give rise to organs of the digestive system and epithelium of the digestive system and respiratory system. Many visible changes in embryonic structure happen throughout gastrulation as

413-432: A multiple birth) signifies the end of stage two. The cow scrambles to her feet (if lying down at this stage), turns round and starts vigorously licking the calf. The calf takes its first few breaths and within minutes is struggling to rise to its feet. The third and final stage of labor is the delivery of the placenta , which is usually expelled within a few hours and is often eaten by the normally herbivorous cow. Birth

472-634: A potential avenue for preventing disease; however, this has been met with widespread condemnation from the scientific community. ART techniques are also used to improve the profitability of agricultural animal species such as cows and pigs by enabling selective breeding for desired traits and/or to increase numbers of offspring. For example, when allowed to breed naturally, cows typically produce one calf per year, whereas IVF increases offspring yield to 9–12 calves per year. IVF and other ART techniques, including cloning via interspecies somatic cell nuclear transfer (iSCNT), are also used in attempts to increase

531-400: A series of involuntary contractions of the muscular walls of the uterus and gradual dilation of the cervix. The active phase of the first stage starts when the cervix is dilated more than about 4 cm in diameter and is when the contractions become stronger and regular. The head (or the buttocks in a breech birth ) of the baby is pushed against the cervix , which gradually dilates until it

590-423: A short gestation and develops further in its mother's womb pouch . It is not only mammals that give birth. Some reptiles, amphibians, fish and invertebrates carry their developing young inside them. Some of these are ovoviviparous , with the eggs being hatched inside the mother's body, and others are viviparous , with the embryo developing inside their body, as in the case of mammals. Humans usually produce

649-465: A similar way one by one usually with less straining than the first usually at 15-60-minute intervals. If a pup has not been passed in 2 hours a veterinarian should be contacted. Stage three is the passing of the placentas. This often occurs in conjunction with stage two with the passing of each offspring. The mother will then usually eat the afterbirth. This is an adaption to keep the den clean and prevent its detection by predators. An infant marsupial

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708-410: A single offspring at a time. The mother's body is prepared for birth by hormones produced by the pituitary gland , the ovary and the placenta . The total gestation period from fertilization to birth is normally about 38 weeks (birth usually occurring 40 weeks after the last menstrual period ). The normal process of childbirth takes several hours and has three stages. The first stage starts with

767-406: A time, although they may have twin or multiple births on occasion. In these large animals, the birth process is similar to that of a human, though in most the offspring is precocial . This means that it is born in a more advanced state than a human baby and is able to stand, walk and run (or swim in the case of an aquatic mammal) shortly after birth. In the case of whales, dolphins and porpoises,

826-544: A very few give birth to offspring that are miniature versions of the adult. The aphid has a complex life cycle and during the summer months is able to multiply with great rapidity. Its reproduction is typically parthenogenetic and viviparous and females produce unfertilized eggs which they retain within their bodies. The embryos develop within their mothers' ovarioles and the offspring are clones of their mothers. Female nymphs are born which grow rapidly and soon produce more female offspring themselves. In some instances,

885-453: Is born in a very immature state. The gestation period is usually shorter than the intervals between oestrus periods. The first sign that a birth is imminent is the mother cleaning out her pouch . When it is born, the infant is pink, blind, furless and a few centimetres long. It has nostrils in order to breathe and forelegs to cling onto its mother's hairs but its hind legs are undeveloped. It crawls through its mother's fur and makes its way into

944-403: Is considered finished when a bone called the cleithrum becomes visible. In animals that hatch from an egg, such as birds, a young animal is typically no longer referred to as an embryo once it has hatched. In viviparous animals (animals whose offspring spend at least some time developing within a parent's body), the offspring is typically referred to as an embryo while inside of the parent, and

1003-408: Is external protrusion of the amniotic sac through the vulva, closely followed by the appearance of the calf's front hooves and head in a front presentation (or occasionally the calf's tail and rear end in a posterior presentation). During the second stage, the cow will usually lie down on her side to push and the calf progresses through the birth canal. The complete delivery of the calf (or calves in

1062-426: Is fully dilated at 10 cm diameter. At some time, the amniotic sac bursts and the amniotic fluid escapes (also known as rupture of membranes or breaking the water). In stage two, starting when the cervix is fully dilated, strong contractions of the uterus and active pushing by the mother expels the baby out through the vagina , which during this stage of labour is called a birth canal as this passage contains

1121-424: Is no longer considered an embryo after birth or exit from the parent. However, the extent of development and growth accomplished while inside of an egg or parent varies significantly from species to species, so much so that the processes that take place after hatching or birth in one species may take place well before those events in another. Therefore, according to one textbook, it is common for scientists to interpret

1180-416: Is termed whelping in dogs. Among dogs , as whelping approaches, contractions become more frequent. Labour in the bitch can be divided into 3 stages. The first stage is when the cervix dilates, causing discomfort and restlessness in the dog. Common signs of this stage are panting, fasting, and/or vomiting. This may last up to 12 hours. Stage two is the passage of the offspring. The amniotic sac looking like

1239-462: Is the next phase of embryonic development, and involves the development of two or more layers of cells (germinal layers). Animals that form two layers (such as Cnidaria ) are called diploblastic, and those that form three (most other animals, from flatworms to humans) are called triploblastic. During gastrulation of triploblastic animals, the three germinal layers that form are called the ectoderm , mesoderm , and endoderm . All tissues and organs of

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1298-401: Is then termed a blastula , or a blastocyst in mammals . The mammalian blastocyst hatches before implantating into the endometrial lining of the womb . Once implanted the embryo will continue its development through the next stages of gastrulation , neurulation , and organogenesis . Gastrulation is the formation of the three germ layers that will form all of the different parts of

1357-737: Is used for addressing fertility concerns in humans and other animals, and for selective breeding in agricultural species. Between the years 1987 and 2015, ART techniques including in vitro fertilization (IVF) were responsible for an estimated one million human births in the United States alone. Other clinical technologies include preimplantation genetic diagnosis (PGD), which can identify certain serious genetic abnormalities, such as aneuploidy , prior to selecting embryos for use in IVF. Some have proposed (or even attempted - see He Jiankui affair ) genetic editing of human embryos via CRISPR-Cas9 as

1416-462: The epidermis or outer covering of a plant, ground tissue will give rise to inner plant material that functions in photosynthesis , resource storage, and physical support, and vascular tissue will give rise to connective tissue like the xylem and phloem that transport fluid, nutrients, and minerals throughout the plant. In heart stage, one or two cotyledons (embryonic leaves) will form. Meristems (centers of stem cell activity) develop during

1475-745: The left atrium , which is pumped into the left ventricle , and then pumped into the main arterial system. As a result of these changes, the blood pressure in the left atrium exceeds the pressure in the right atrium, and this pressure difference forces the foramen ovale to close separating the left and right sides of the heart. The umbilical vein , umbilical arteries , ductus venosus and ductus arteriosus are not needed for life in air and in time these vessels become ligaments (embryonic remnants). Large mammals , such as primates , cattle , horses , some antelopes , giraffes , hippopotamuses , rhinoceroses , elephants , seals , whales , dolphins , and porpoises , generally are pregnant with one offspring at

1534-429: The uterus are not obvious externally, but the cow may be restless. She may appear agitated, alternating between standing and lying down, with her tail slightly raised and her back arched. The fetus is pushed toward the birth canal by each contraction and the cow's cervix gradually begins to dilate. Stage one may last several hours, and ends when the cervix is fully dilated. Stage two can be seen to be underway when there

1593-551: The Tarangire National Park of Tanzania, estimated to have been born in August 2017. Birthing in cattle is typical of a larger mammal. A cow goes through three stages of labor during normal delivery of a calf. During stage one, the animal seeks a quiet place away from the rest of the herd. Hormone changes cause soft tissues of the birth canal to relax as the mother's body prepares for birth. The contractions of

1652-527: The body. Neurulation forms the nervous system , and organogenesis is the development of all the various tissues and organs of the body. A newly developing human is typically referred to as an embryo until the ninth week after conception, when it is then referred to as a fetus . In other multicellular organisms, the word "embryo" can be used more broadly to any early developmental or life cycle stage prior to birth or hatching . First attested in English in

1711-444: The cells such as RNAs and proteins actively promote key developmental processes such as gene expression, cell fate specification, and polarity. Before implanting into the uterine wall the embryo is sometimes known as the pre-implantation embryo or pre-implantation conceptus . Sometimes this is called the pre-embryo a term employed to differentiate from an embryo proper in relation to embryonic stem cell discourses. Gastrulation

1770-494: The cells that make up the different germ layers migrate and cause the previously round embryo to fold or invaginate into a cup-like appearance. Past gastrulation, an embryo continues to develop into a mature multicellular organism by forming structures necessary for life outside of the womb or egg. As the name suggests, organogenesis is the stage of embryonic development when organs form. During organogenesis, molecular and cellular interactions prompt certain populations of cells from

1829-404: The creation of a zygote, a single cell resulting from the fusion of gametes (e.g. egg and sperm). The development of a zygote into a multicellular embryo proceeds through a series of recognizable stages, often divided into cleavage, blastula, gastrulation, and organogenesis. Cleavage is the period of rapid mitotic cell divisions that occur after fertilization. During cleavage, the overall size of

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1888-459: The different germ layers to differentiate into organ-specific cell types. For example, in neurogenesis, a subpopulation of cells from the ectoderm segregate from other cells and further specialize to become the brain, spinal cord, or peripheral nerves. The embryonic period varies from species to species. In human development, the term fetus is used instead of embryo after the ninth week after conception, whereas in zebrafish , embryonic development

1947-406: The embryo begins its existence attached to the inside of the archegonium on a parental gametophyte from which the egg cell was generated. The inner wall of the archegonium lies in close contact with the "foot" of the developing embryo; this "foot" consists of a bulbous mass of cells at the base of the embryo which may receive nutrition from its parent gametophyte. The structure and development of

2006-427: The embryo does not change, but the size of individual cells decrease rapidly as they divide to increase the total number of cells. Cleavage results in a blastula. Depending on the species, a blastula or blastocyst stage embryo can appear as a ball of cells on top of yolk, or as a hollow sphere of cells surrounding a middle cavity . The embryo's cells continue to divide and increase in number, while molecules within

2065-437: The expectation that a small number may survive to become mature individuals. Terrestrial invertebrates may also produce large numbers of eggs, a few of which may avoid predation and carry on the species. Some fish, reptiles, and amphibians have adopted a different strategy and invest their effort in producing a small number of young at a more advanced stage which are more likely to survive to adulthood. Birds care for their young in

2124-406: The female egg cell by the male sperm cell . The resulting fusion of these two cells produces a single-celled zygote that undergoes many cell divisions that produce cells known as blastomeres . The blastomeres (4-cell stage) are arranged as a solid ball that when reaching a certain size, called a morula , (16-cell stage) takes in fluid to create a cavity called a blastocoel . The structure

2183-520: The genera Tiliqua and Corucia , give birth to live young that develop internally, deriving their nourishment from a mammal-like placenta attached to the inside of the mother's uterus. In a recently described example, an African species, Trachylepis ivensi , has developed a purely reptilian placenta directly comparable in structure and function to a mammalian placenta. Vivipary is rare in snakes , but boas and vipers are viviparous, giving birth to live young. The majority of insects lay eggs but

2242-463: The genus Nectophrynoides are ovoviviparous, developing through the larval stage inside the mother's oviduct and eventually emerging as fully formed juveniles. A more developed form of viviparity called placental viviparity is adopted by some species of scorpions and cockroaches, certain genera of sharks , snakes and velvet worms . In these, the developing embryo is nourished by some form of placental structure. The earliest known placenta

2301-575: The largest collection of plant reproductive tissue, with more than a million samples stored at −18 °C (0 °F). Fossilized animal embryos are known from the Precambrian , and are found in great numbers during the Cambrian period. Even fossilized dinosaur embryos have been discovered. Birth Birth is the act or process of bearing or bringing forth offspring , also referred to in technical contexts as parturition . In mammals,

2360-457: The mid-14c., the word embryon derives from Medieval Latin embryo , itself from Greek ἔμβρυον ( embruon ), lit. "young one", which is the neuter of ἔμβρυος ( embruos ), lit. "growing in", from ἐν ( en ), "in" and βρύω ( bruō ), "swell, be full"; the proper Latinized form of the Greek term would be embryum . In animals, fertilization begins the process of embryonic development with

2419-514: The morphological characteristics of neurons, such as rounded cell bodies and processes . NTERA-2 cells can also produce a small number of oligodendrocyte -type cells, but they cannot differentiate into astrocytes . Because of their similarity to human embryonic stem cells , NTERA-2 cells are used to study the dopaminergic differentiation of neuronal precursor cells. They have also been proposed as an in vitro test system for developmental neurotoxicity . NTERA-2 cells were originally isolated from

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2478-412: The nest and provide for their needs after hatching and it is perhaps unsurprising that internal development does not occur in birds, given their need to fly. Ovoviviparity is a mode of reproduction in which embryos develop inside eggs that remain in the mother's body until they are ready to hatch. Ovoviviparous animals are similar to viviparous species in that there is internal fertilization and

2537-449: The numbers of endangered or vulnerable species, such as Northern white rhinos , cheetahs , and sturgeons . Cryoconservation of genetic resources involves collecting and storing the reproductive materials, such as embryos, seeds, or gametes, from animal or plant species at low temperatures in order to preserve them for future use. Some large-scale animal species cryoconservation efforts include " frozen zoos " in various places around

2596-419: The placenta for sustenance including gaseous exchange and the unborn baby's blood bypasses the lungs by flowing through the foramen ovale , which is a hole in the septum dividing the right atrium and left atrium . After birth the umbilical cord is clamped and cut, the baby starts to breathe air, and blood from the right ventricle starts to flow to the lungs for gaseous exchange and oxygenated blood returns to

2655-417: The pouch. Here it fixes onto a teat which swells inside its mouth. It stays attached to the teat for several months until it is sufficiently developed to emerge. Joeys are born with "oral shields"; in species without pouches or with rudimentary pouches these are more developed than in forms with well-developed pouches, implying a role in maintaining the young attached to the mother's nipple. Many reptiles and

2714-418: The process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the fetus at a developmental stage when it is ready to feed and breathe. In some species, the offspring is precocial and can move around almost immediately after birth but in others, it is altricial and completely dependent on parenting. In marsupials , the fetus is born at a very immature stage after

2773-432: The rest of the embryo varies by group of plants. Since all land plants create embryos, they are collectively referred to as embryophytes (or by their scientific name, Embryophyta). This, along with other characteristics, distinguishes land plants from other types of plants, such as algae , which do not produce embryos. Embryos from numerous plant and animal species are studied in biological research laboratories across

2832-412: The scope of embryology broadly as the study of the development of animals. Flowering plants ( angiosperms ) create embryos after the fertilization of a haploid ovule by pollen . The DNA from the ovule and pollen combine to form a diploid, single-cell zygote that will develop into an embryo. The zygote, which will divide multiple times as it progresses throughout embryonic development, is one part of

2891-403: The single calf is normally born tail first which minimizes the risk of drowning. The mother encourages the newborn calf to rise to the surface of the water to breathe. Large mammals which give birth to twins is much more rare, but it does occur occasionally even for mammals as large as elephants. In April 2018, approximately 8-month old elephant twins were sighted joining their mother's herd in

2950-498: The structures of the mature plant, such as the stem, leaves, and roots. The larger basal cell will give rise to the suspensor, which connects the embryo to the endosperm so that nutrients can pass between them. The plant embryo cells continue to divide and progress through developmental stages named for their general appearance: globular, heart, and torpedo. In the globular stage, three basic tissue types (dermal, ground, and vascular) can be recognized. The dermal tissue will give rise to

3009-452: The torpedo stage, and will eventually produce many of the mature tissues of the adult plant throughout its life. At the end of embryonic growth, the seed will usually go dormant until germination. Once the embryo begins to germinate (grow out from the seed) and forms its first true leaf, it is called a seedling or plantlet. Plants that produce spores instead of seeds, like bryophytes and ferns , also produce embryos. In these plants,

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3068-441: The vast majority of invertebrates, most fish, amphibians and all birds are oviparous , that is, they lay eggs with little or no embryonic development taking place within the mother. In aquatic organisms, fertilization is nearly always external with sperm and eggs being liberated into the water (an exception is sharks and rays, which have internal fertilization ). Millions of eggs may be produced with no further parental involvement, in

3127-420: The walls of the oviduct. The Lamniforme sharks practice oophagy , where the first embryos to hatch consume the remaining eggs and sand tiger shark pups cannibalistically consume neighbouring embryos. The requiem sharks maintain a placental link to the developing young, this practice is known as viviparity . This is more analogous to mammalian gestation than to that of other fishes. In all these cases,

3186-851: The world to learn about topics such as stem cells , evolution and development , cell division , and gene expression . Examples of scientific discoveries made while studying embryos that were awarded the Nobel Prize in Physiology or Medicine include the Spemann-Mangold organizer , a group of cells originally discovered in amphibian embryos that give rise to neural tissues, and genes that give rise to body segments discovered in Drosophila fly embryos by Christiane Nüsslein-Volhard and Eric Wieschaus . Creating and/or manipulating embryos via assisted reproductive technology (ART)

3245-753: The world, including in the UK's Frozen Ark , the Breeding Centre for Endangered Arabian Wildlife (BCEAW) in the United Arab Emirates, and the San Diego Zoo Institute for Conservation in the United States. As of 2018, there were approximately 1,700 seed banks used to store and protect plant biodiversity, particularly in the event of mass extinction or other global emergencies. The Svalbard Global Seed Vault in Norway maintains

3304-412: The young are born alive and fully functional. The majority of caecilians are ovoviviparous and give birth to already developed offspring. When the young have finished their yolk sacs they feed on nutrients secreted by cells lining the oviduct and even the cells themselves which they eat with specialist scraping teeth. The Alpine salamander ( Salamandra atra ) and several species of Tanzanian toad in

3363-416: The young are born in an advanced state, but differ in that there is no placental connection and the unborn young are nourished by egg yolk . The mother's body provides gas exchange (respiration), but that is largely necessary for oviparous animals as well. In many sharks the eggs hatch in the oviduct within the mother's body and the embryos are nourished by the egg's yolk and fluids secreted by glands in

3422-643: Was found recently in a group of extinct fishes called placoderms . A fossil from Australia's Gogo Formation , laid down in the Devonian period, 380 million years ago, was found with an embryo inside it connected by an umbilical cord to a yolk sac . The find confirmed the hypothesis that a sub-group of placoderms, called ptyctodontids , fertilized their eggs internally. Some fishes that fertilize their eggs internally also give birth to live young, as seen here. This discovery moved our knowledge of live birth back 200 million years. The fossil of another genus

3481-518: Was found with three embryos in the same position. Placoderms are a sister group of the ancestor of all living jawed fishes ( Gnathostomata ), including both chondrichthyans , the sharks & rays, and Osteichthyes , the bony fishes. Among lizards, the viviparous lizard Zootoca vivipara , the Jackson's chameleon , slow worms and many species of skink are viviparous, giving birth to live young. Some are ovoviviparous but others such as members of

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