Embryo and embryonic development Photo by: Noel Powell The term embryo applies to the earliest form of life, produced when an egg female reproductive cell is fertilized by a sperm male reproductive cell; semen. The fertilized egg is called a zygote. Shortly after fertilization, the zygote begins to grow and develop.
Embryonic development of salamander, circa the s Embryos and one tadpole of the wrinkled frog Rana rugosa In animals, the development of the zygote into an embryo proceeds through specific recognizable stages of blastulagastrulaand organogenesis.
The blastula stage typically features a fluid-filled cavity, the blastocoelsurrounded by a sphere or sheet of cells, also called blastomeres. In a placental mammalan ovum is fertilized in a fallopian tube through which it travels into the uterus.
An embryo is called a fetus at a more advanced stage of development and up until birth or hatching. In humans, this is from the eleventh week of gestation.
However, animals which develop in eggs outside the mother's body, are usually referred to as embryos throughout development; e. In triploblastic organisms, the three germ layers are called endodermectodermand mesoderm. The position and arrangement of the germ layers are highly species-specific, however, depending on the type of embryo produced.
In vertebratesa special population of embryonic cells called the neural crest has been proposed as a "fourth germ layer", and is thought to have been an important novelty in the evolution of head structures.
During organogenesis, molecular and cellular interactions between germ layers, combined with the cells' developmental potential, or competence to respond, prompt the further differentiation of organ-specific cell types. Modern developmental biology is extensively probing the molecular basis for every type of organogenesis, including angiogenesis formation of new blood vessels from pre-existing oneschondrogenesis cartilagemyogenesis muscleosteogenesis boneand many others.
Sporophyte The inside of a Ginkgo seed, showing the embryo In botanya seed plant embryo is part of a seedconsisting of precursor tissues for the leaves, stem see hypocotyland root see radicleas well as one or more cotyledons.
Once the embryo begins to germinate —grow out from the seed—it is called a seedling plantlet. Bryophytes and ferns also produce an embryo, but do not produce seeds. In these plants, 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 the rest of the embryo varies by group of plants. Once the embryo has expanded beyond the enclosing archegonium, it is no longer termed an embryo.
Research and technology[ edit ] Embryos are used in various fields of research and in techniques of assisted reproductive technology. An egg may be fertilized in vitro and the resulting embryo may be frozen for later use. The potential of embryonic stem cell research, reproductive cloningand germline engineering are currently being explored.
Prenatal diagnosis or preimplantation diagnosis enables testing embryos for diseases or conditions. Cryoconservation of animal genetic resources is a practice in which animal germplasms, such as embryos are collected and stored at low temperatures with the intent of conserving the genetic material.
The embryos of Arabidopsis thaliana have been used as a model to understand gene activation, patterning, and organogenesis of seed plants. This method will help scientists to more deeply study the very first moments of the process of the birth of a new life, which, in turn, can lead to the emergence of new effective methods to combat infertility and other genetic diseases.
Fossil embryos Fossilized animal embryos are known from the Precambrianand are found in great numbers during the Cambrian period.
Even fossilized dinosaur embryos have been discovered. Miscarriage and Abortion A complete spontaneous abortion at about 6 weeks from conceptioni.
When this happens naturally, it is called spontaneous abortion or miscarriage. The most common natural cause of miscarriage is chromosomal abnormality in animals  or genetic load in plants.
This can also disturb the pregnancy, causing harm to the second embryo. Genetic strains which miscarry their embryos are the source of commercial seedless fruits.
Abortion is the process of artificially non-naturally removing the embryo through deliberate pharmaceutical or surgical methods.You are correct. I am using a reworded form of the SLED test. I was trained by Scott Klusendorf 13 years ago and I generally recommend his material.
Scott is a theist but he nevertheless can make a strong secular case against abortion that has served as fuel to my own. acquired trait: A phenotypic characteristic, acquired during growth and development, that is not genetically based and therefore cannot be passed on to the next generation (for example, the large.
Most organs begin to form about 3 weeks after fertilization, which equals 5 weeks of pregnancy (because doctors date pregnancy from the first day of the woman's last menstrual period, which is typically 2 weeks before fertilization). Fertilization, the joining of sperm and egg, typically occurs in the fallopian tube, after sperm have made the long swim up through the vagina, past the cervix, and through the uterus.
Fertilization brings together the chromosomes from each parent, creating the first cell, or zygote, of the new human. Because a human egg lives no [ ]. This page shows some key events of human development during the embryonic period of the first eight weeks (weeks 1 - 8) following fertilization.
This period is also considered the organogenic period, when most organs within the embryo have begun to form.
Fetal development - from conception to term. Gestational Age 8 weeks ( months). Embryonic Age 6 weeks. The average embryo at 8 weeks is inches ( cm) long and weighs less than 1/2 ounce (15 grams).. The embryo is about the size of a bean. The fingers and toes are developing.