What is an Embryo?

Embryos are larvae in the first two months of pregnancy. Early blastocyst and embryo development and embryo development are a continuous process. During the somite period, all three germ layers changed. The ectoderm is recessed into a sulcus in the midline of the back, called the nerve sulcus, and the two sides of the sulcus are called nerve ridges. The nerve ridge gradually approaches and heals, causing the nerve to evolve into a neural tube that runs through the embryo. Neural tubes and spines will evolve into the nervous system in the future. The endoderm curls into a tube along with the embryo, which is called the gut, and the gut is divided into the foregut, midgut, and hindgut depending on the part. ^[1]

Embryo

(Biological term)

The development of an embryo is a very delicate and complex process. It is a process in which cells and tissues are differentiated in a certain order. Any disturbance in this process will cause various deformities. Especially when the organs are rapidly differentiated and developed, they are most susceptible to the interference of teratogenic factors.

Human embryo pair

I. Autoimmune antibodies and

Stem cells are the basic forming elements of human tissues. Researchers around the world are actively conducting research to transform stem cells into new and healthy cells to repair the dying heart, liver, brain, and other organs.

Stem cells can be taken from adults or from embryos. The biggest difference between embryonic stem cells and adult stem cells is that embryonic stem cells are the first human cells, which have flexibility and adaptability compared to adult stem cells, and their development potential is naturally endless. Researchers believe that stem cells extracted from embryos can be transformed into any of the more than 200 cellular tissues in the body. Embryonic stem cell transplantation

1. The meaning of embryonic stem cells: a type of cells isolated from early embryos [blastocysts] or primitive gonads [fetus], also known as ES or EK cells.

2. Features: Small in size, large in nucleus and obvious in nucleoli; functionally totipotent in development, it can differentiate into any kind of tissue cells in adult animals. [In vitro culture, ES cells can only proliferate and not differentiate]

3 Application: It is used to treat human diseases, such as using ES cells to induce their differentiation into new tissue cell characteristics. Transplantation of ES cells can repair necrotic or degraded sites.

Embryo engineering refers to a variety of micromanipulation and processing techniques for animal early embryos or gametes, such as embryo transfer, in vitro fertilization, embryo segmentation, and embryonic stem cell culture. The embryos obtained after processing need to be transferred to female animals to produce offspring to meet the various needs of humans.

Basic process of animal embryo development

1. The fertilization site is the mother's fallopian tube.

2. Cleavage stage: Features: Cells undergo mitosis and the number of cells continues to increase, but the overall volume of the embryo does not increase or decreases slightly.

3 Mulberry embryo: Features: When the number of embryonic cells reaches about 32, the embryo forms a dense cell cluster, similar to mulberry. Are totipotent cells.

4 Blastocyst: Features: Cells begin to differentiate (cell totipotency is still high during this period). The larger cells that gather at one end of the embryo are called inner cell clusters, which will develop into various tissues of the fetus in the future. The middle cavity is called the blastocyst cavity.

5. Gut embryo: Features: With the differentiation of the three germ layers, it has a blastocyst cavity and a gut cavity.

Application of Embryo Engineering

1. In vitro fertilization and early culture of embryos

(1) Collection and culture of oocytes: the main method: treatment with gonadotrophins to make them release more eggs, and then, from

The embryo (embryo) of a new generation of plant body developed from a fertilized egg (zygote). Is the most important part of the seed. The mesoderm is the only living part in the seed, and there are preliminary organ differentiation, including the germ, hypocotyl, radicle and cotyledon.

1. The germ is located at the top of the embryo and is the primitive body of the future plant stem and leaf system, which will develop into the above-ground part of the plant in the future.

2. The hypocotyl is located between the germ and the radicle, and is connected to the cotyledon, and later forms a rhizome-connected part. During the germination of the seed, the growth of the hypocotyl greatly helped the emergence of cotyledons in some seeds.

3 The radicle is located below the hypocotyl and provides nutrition to the embryo. It is conical and is the prototype of the main root in the seed. It can develop into the main root of the plant in the future and form the root system of the plant. (4) The embryo is composed of germ, hypocotyl, radicle, and cotyledon. The cotyledon is the leaf of the embryo, or a temporary leaf, usually 1 or 2 pieces, located on the side of the hypocotyl. Among the angiosperms, the embryo with a cotyledon is called a monocotyledon. With 2 cotyledons, called dicotyledons, the cotyledons fall off after providing nutrients. Gymnosperm embryos have multiple cotyledons, such as pines with 3 to 18 cotyledons, to provide nutrition for seeds without endosperm, or to transport nutrients for seeds with endosperm.

From sperm to egg combination, embryo implantation, fetal development to childbirth, this period is called the gestation period, and for newly formed living individuals, it is called the embryo stage. Pregnant sows are both producers of piglets and the largest consumers of nutrients. The gestation period accounts for about two-thirds of the entire sow's production cycle. therefore,

The embryo survival rate is expressed as litter size. There are many factors that affect the survival rate of embryos, and they are also very complicated, mainly including the following.

In 1998, Clinton signed a bill that barred funding for human-animal egg cell nuclear transfer research. You may remember South Korean scientist Huang Yuxi, who had successfully cloned a dog for the first time and claimed to have cloned a human embryo. But his claimed research on human embryo cloning was revealed to be fraudulent and paid for the purchase of human eggs, which is not allowed by South Korean law.

The use of eggs from other animals can alleviate the situation of limited human egg resources to some extent. China is the first country in the world to carry out this type of research. As early as August 2003, a research team led by Sheng Huizhen, who was the director of the Developmental Biology Research Center of Xinhua Hospital affiliated to the Shanghai Jiao Tong University School of Medicine, used cloning technology to remove waste Cells were extracted from the skin tissues and fused into rabbit enucleated oocytes. Hundreds of fused embryos were successfully obtained and embryonic stem cells were extracted. (The study was discontinued)

On September 5, 2007, the UK s Artificial Fertilization and Embryology Authority (HFEA) passed a bill that allows Type IV human-animal integration research to be conducted under strict supervision, and provides for the use of this technology to obtain Embryos must be destroyed before the 14th day of development. Since then, three laboratories from King's College London, Newcastle University and Warwick University have been approved for such research. This is also the origin of the "within three years" mentioned in the Daily Mail. The 155 hybrid embryos are the result of the fourth type of technology. In other words, they are all legitimate, let alone secrets. On April 1, 2008, the Lyle Armstrong team at Newcastle University created a human-cow hybrid embryo, which caused a great response in the media. The Daily Mail on April 2 Japan also followed up and issued a report.

Although there are many types of animals, embryonic development still has a similar process, which can be divided into stages such as fertilization, cleavage, mulberry embryo, blastocyst, gastrula embryo and organ formation. In addition, during the development of vertebrate embryos, characteristics common to various animals will first appear (such as skin), and then gradually develop specialized structures (such as fish scales), and between more complex species and more primitive species It is quite similar at first, and then gradually increases with the development time [3].

Embryo fertilization

See also: Fertilization has some coats around the cell membrane of the egg. The first layer is composed of glycoproteins, commonly called the yolk membrane, and in mammals it is called the zona pellucida. When a sperm enters the egg, the eggs of most species form a protection that prevents other sperm from entering the egg. A few species, such as certain birds and reptiles, allow other sperm to enter, but still only one sperm can interact with the nucleus of the egg. The sperm fuses with the nucleus of the egg and forms a fertilized egg with a double set of chromosomes.

In replication technology, the process of replacing fertilization is to remove the nucleus of an egg and implant the somatic cells into the egg. Animals that reproduce asexually usually do not need to undergo cell fusion, but directly produce larvae by budding or dividing.

Embryo cleavage

The process of cleavage.

See also: Fertilized eggs are formed after cleavage of spermatozoa and eggs. Due to the asymmetrical distribution of yolk, fertilized eggs can be divided into animal poles (which will develop into ectoderm) and plant poles (which will develop into mesoderm and endodermis). Germ layer). During the cleavage stage, the egg divides into two cells first, and then the cells usually multiply one after the other. However, for mammals, sometimes they do not divide at the same time and cause only an odd number of cells. At this stage, the total volume of the embryo is roughly constant.

The stage of cell division into 16 to 64 cells is called morula. At this stage, the frequency of division of the animal pole will exceed that of the cell population with yolk near the plant pole. At the stage of more than 128 cells, called a blastula, a blastocyst cavity will be formed in the inner part of the blastocyst near the poles of the animal.

Different species have different cleavage methods, which can be divided into holoblastic cleavege and meroblastic cleavage, which can be subdivided into many different methods. Such as invertebrate cleavage and spiral cleavage, mammalian rotary division and so on.

Embryonic gastrula

See also: When the gastrointestinal embryo divides into a blastocyst, it undergoes a morphogenetic process known as gastrointestinal formation, and then forms a gastrointestinal embryo. There are many different ways in which the gut is formed, which can be roughly divided into 5 types:

Invagination-Cells in the plant poles are recessed into the embryo, and finally pass through the embryo and open at the other end. It is worth noting that the later openings will become the mouth of the animal, and the original depression will become the anus. Stomata are named after them, such as the endoderm of sea urchins.

Involution-The cells in the plant poles proliferate inward along the inner wall of the blastocyst cavity, and the outer parts are replaced by animal pole cells, such as the mesoderm of a frog.

Ingression-Cells in specific places move to other specific locations after division, such as the mesoderm of sea urchins, and neuroblasts of fruit flies.

Delamination-The outer layer of cells slides. Originally, only one layer of cells proliferated into two layers, such as mammals and birds' hypoblast.

Epiboly-The outer layer of cells expands, squeezes into the depression of the plant pole, and gradually moves towards the inner wall of the blastocyst cavity into two layers, such as the ectoderm of frogs and sea urchins.

Animal embryos use these five methods to form a combination of ectoderm, mesoderm, and endoderm, and these three germ layers later form various cells. For example, developed from endoderm, mesenchymal cells with multiple potentials can differentiate into fibroblasts, chondrocytes, osteoblasts, adipocytes, smooth muscle cells, striated muscle cells, hematopoietic cells, and so on.

Embryonic organ formation

The process of ectoderm, mesoderm and endoderm forming various tissues and organs is called organogenesis, also called organogenesis. Take the frog's embryo as an example. In the early stage of organ formation, the ectoderm will sag inward after the process, forming the neural spine and neural tube; the mesoderm will form the somite and spine, surrounded by the mesoderm The space is called the body cavity.