3 stages of embryo development

What Are the 3 Stages of Embryonic Development? Get the

Embryonic Development - Embryolog

The three main stages of development are ovulation /conception, embryonic development and development of the fetus. Ovulation usually occurs around week two of the cycle. In the two weeks prior to conception, the body is readying the womb for a potential pregnancy by growing a layer of rich, blood perfused tissue Embryonic Development. Starting in the second week after fertilization, the embryo starts to develop distinct cell layers, form the nervous system, make blood cells, and form many organs. By the end of the embryonic stage, most organs have started to form, although they will continue to develop and grow in the next stage (that of the fetus) Hi Everyone, Prenatal development consists of 3 stages, the germinal period, embryonic period, and fetal period. The germinal period begins at fertilization until implantation of the fertilized egg into the uterine wall. During this first stage, the zygote goes through mitosis and developed into a blastocyst and trophoblast. The second stage is the embryonic period at implantation, which is. 3- Embryology; 4- Endomertriosis and Endometrium; 5- Fertility Preservation; 6- Quality and Safety in ART; 7- Reproductive Genetics; 8- Reproductive Surgery; 9- Stem cells; 10- Obstetrics and Gynecology; 11- Various videos in biology and medical sciences; Stages of Embryo Development.

What are the three phases of embryonic development in

  1. of 17. human embryonic development embryo stage egg fertilization fetus stages prenatal baby stages blastocyst development embryo 3d embryonic stage medical fetal development embryo development. Try these curated collections
  2. Stages of Plant Development • Asymetric Early Cell Division -Embryo -Suspensor - transfers food to embryo -Cells near suspensor become roo
  3. In this section, we'll cover the pre-embryonic and embryonic stages of development, which are characterized by cell division, migration, and differentiation. By the end of the embryonic period, all of the organ systems are structured in rudimentary form, although the organs themselves are either nonfunctional or only semi-functional
VIDEO: 3D animation show how face forms in womb - NY Daily

Stages of Development of the Fetus - Women's Health Issues

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  2. Embryo Definition. An embryo refers to the early developmental stage of eukaryotic organisms following the fertilization of an egg (derived from a female) by sperm (derived from a male) as a method of sexual reproduction.In animals, the initial diploid cell that results from the fusion of the egg and the sperm contains half the genetic information (DNA) from each of the parental cells and is.
  3. Embryo development refers to the different stages in the development of an embryo. Embryonic development of plants and animals vary. Even in animals, every species undergoes different stages during embryonic development. Let us learn about human embryonic development and various stages. After fertilization, the zygote is formed
  4. Day 1 in the IVF Lab - Number of Eggs Fertilized Known. Day 2 in the IVF Lab - Embryo Divides. Day 3 in the IVF Lab - Embryo Grading and Potential Transfer. Day 4 in the IVF Lab - From Cleavage Stage to Blastocyst. Day 5 in the IVF Lab - Blastocysts are Graded and Transferred or Frozen

3rd week of embryonic development: Steps and processes

The complexity of the development cannot be understood without training in embryology. When the egg is laid, some embryonic development has occurred and usually stops until proper cell environmental conditions are established for incubation to resume. At first, all the cells are alike, but as the embryo develops, cell differences are observed These initial stages, known collectively as embryogenesis, carry the new organism from a single cell all the way to a fetus. The process is shown in the image below. During this trimester of prenatal development, the embryo is especially sensitive to any environmental toxins or chemicals that the mother comes in contact with. This is especially.

18-hour-old embryo, particularly in cross-species comparisons. An earlier staging series for zebrafish, although less complete than the present one, fairly accurately por- trays the first third (or 1st day) of embryonic develop- ment, and includes useful sets of photographs (Hisaoka and Battle, 1958; Hisaoka and Firlit, 1960). Warga an We describe a series of stages for development of the embryo of the zebrafish, Danio (Brachydanio) rerio. We define seven broad periods of embryogenesis—the zygote, cleavage, blastula, gastrula, segmentation, pharyngula, and hatching periods Development of foetus is complete by 39 to 40 weeks, which is a normal full-term pregnancy. The Embryonic Development occurring during Pregnancy is usually calculated in Weeks starting from the first day of last menstral period. The three main stages of a baby's development in the womb are zygote, embryo, and fetus The neural tube forms along the back of the embryo, developing into the spinal cord and brain. Fetal Stage (Weeks 9-40) When the organism is about nine weeks old, the embryo is called a fetus. At this stage, the fetus is about the size of a kidney bean and begins to take on the recognizable form of a human being as the tail begins to.

Informed Consent: Fetal Development

In still later stages, the development of the appendages presents easily distinguishable and convenient characters for the definition of normal stages. Although morphological characters appear to be the best criteria for establishing the stage of development of an embryo, there are certain limitations even to this approach Stages of fetal growth and development 1. Stages of Fetal Growth and DevelopmentHannilore Villamor, RN 2. The growth and development of the fetus is typically divided into three stages• Preembryonic Stage: Fertilization to 2 to 3 Weeks• Embryonic Stage: 4 to 8 Weeks Gestation• Fetal Stage: 9 Weeks to Birth 3 ADVERTISEMENTS: Let us make an in-depth study of Embryo. After reading this article you will learn about: 1. Meaning of Embryo 2. Development of Embryo in Dicots 3. Development of Embryo in Monocots 4. Incompatibility 5. Special Modes of Reproduction. Meaning of Embryo: After fertilization, the fertilized egg is called zygote or oospore which develops [

Blastocyst Day 5-6 Movie - Embryology

Implantation of the embryo takes approximately 4-5 days, from the time the blastocyst hatches until the trofoectoderm completely invades the endometrium. This occurs between days 5 and 8 of embryonic development, i.e., this is the time it takes for the embryo to implant after fertilization between the egg and sperm. Suggested for yo Camera lucida sketches of the embryo at selected stages. Fig. 2. Rates of development for embryos incubated at 25C and 33C. Fig. 3. The zygote period. Fig. 4. Embryos during the cleavage period. Fig. 5. Idealized blastomere number as a function of time. Fig. 6. Diagrammatic animal polar views of the planes of the first 5 cleavages. Fig. 7.

Follow your baby's development week by week, from conception to labor, in these amazingly detailed, doctor-reviewed images. Illustrations by 3 Dart LLC. 2 weeks: Fertilization. Your ball of cells is now officially an embryo. You're now about 4 weeks from the beginning of your last period The Stages of Early Embryonic Development. Fertilization is defined as a process where gametes (an egg and sperm) join together to form a full zygote. Both the sperm and egg contain a single set.

Embryo grading is a tool used by IVF specialists to improve your chances of conception and pregnancy. Your IVF lab will carefully grade your embryos, selecting the ones with the best potential for viable implantation. Grading occurs on both day 3 and day 5, according to different sets of criteria. Implantation is usually done on either day 3 or. In the human embryo the maximum diameter increases from 100-200 μm at stages 2 and 3 to 300-450 μm at stage 5a. Embryos of stage 3 are believed to be about 4 days in age. In vitro embryos of stage 1 have been recorded at 9-32 hours after insemination; stage 2 at 22-40 hours (2 cells), 32-45 hours (4 cells), and 48 hours (8 cells); stage 3 at. The early stages of embryonic development are also crucial for ensuring the fitness of the organism. Fertilization. Fertilization, pictured in Figure 24.23 a is the process in which gametes (an egg and sperm) fuse to form a zygote. The egg and sperm each contain one set of chromosomes. To ensure that the offspring has only one complete diploid.

Human embryonic development - Wikipedi

(A) Total number of unique and shared proteins in ND (left column) and DE embryos (right column) at 1-cell, 16-cell, 32-cell, oblong, and bud developmental stages. ( B ) Specificity and overlap of the identified proteins across the critical stages of early embryonic development: Cleavage stages (1-, 16-, and 32-cell stages combined), maternal. The structural changes in a zygote leading to the formation of adult form is embryonic development. During this a single celled egg transforms into a multicellular and fully formed organism. The phases include-1. Gametogenesis 2. Fertilisation 3. Early development- including- cleavage, blastulation and gastrulation. 4. Differentiation and. The stages of blastocyst embryo development are divided into four grades. Grade 1: The embryo with a blastocoel cavity less than 50% of the embryo volume. Grade 2: The embryo with a blastocoel cavity as much as 50% of the embryo volume or more. Grade 3: Embryo that has a blastocoel cavity which has fulfilled that all embryos and zona pellucida (ZP) appeared to be thinner than embryo on day 3

Embryonic development - Wikipedi

Week 1 of the development stages of the embryo. This week is the equal of the Carnegie stage 1,2,3 and 4. During this time the embryo looks nothing like a real baby. In fact it looks just like the egg. However you should know that the cells already begin to multiply and this is considered to be the first step of the development of the future baby Stages are named, not numbered as in most other series, providing for flexibility and continued evolution of the staging series as we learn more about development in this species. The stages, and their names, are based on morphological features, generally readily identified by examination of the live embryo with the dissecting stereomicroscope At this stage of prenatal development the embryo is a blastocyst. In humans, implantation of a fertilized ovum occurs between 6 to 12 days after ovulation. In preparation for implantation, the blastocyst sheds its outside layer, the zona pellucida, and is replaced by a layer of underlying cells called the trophoblast Here are the stages of development of embryo: 1.Pronuclear stage on the first day (fertilized egg) 2.Two to four-cell stage on the second day 3.Eight-cell stage on the third day 4.Morula stage on the fourth day and 5.Blastocyst stage on the fifth day To Play. After 16-20 hours the oocytes are examined for the success of fertilization. All the embryos formed at this stage are allowed to grow in a laboratory incubator for up to five days. At this.

File:Bat embryo stage 12-17

The embryo in this video is under examination for in vitro fertilization (IVF). Watch as the embryo splits into a two-cell, then a three- and four-cell embry.. 3. What are the animal pole and the vegetal pole of vertebrate eggs? The animal pole of a telolecithal egg is t he portion of the egg wi th little vitellus.It is opposite to the vegetal pole, which is the region where the yolk is concentrated.. Embryonic Development Review - Image Diversity: animal and vegetal pole The embryonic stage is apparent in the 3 week old embryo. The lung bud develops from the foregut and in communication with it. Separation of the two lung buds comes about with fusion of the esophagotracheal ridges to form the esophagotracheal septum (Figure 12-1). When the embryo is 5 weeks old, two primary lung buds are identifiable. The lung.

The concept of Embryology in the Quran claims that a scientifically accurate account of embryological development is available in the Quran. Apologists, Sheikhs, and the larger Muslim community regard the mention of embryological stages in the Quran to be a scientific miracle of Islam and evidence of claims to its divine origin. However, critics claim the verses to be scientifically inaccurate. Dr. Swati Dongre (https://www.elawoman.com/thane/doctor/dr-swati-dongre) is trained Gynecologist and Infertility Specialist. She did her MBBS from lofty Gove..

the embryos can be conveniently reared in finger bowls or in stirring cultures. The major stages of early development in the sea urchin are shown in 3.1-3.15, and each stage will be discussed in turn in the following sections. Mature sea urchin eggs, unlike eggs from many other animals, have complete Baby's Development at 4 Weeks. After 4 weeks, the basic structures of the embryo have begun to develop into separate areas that will form the head, chest, abdomen, and the organs contained within them. Small buds on the surface will become arms and legs. A home pregnancy test should be positive at this stage of development (most tests claim. The embryo is an early developmental stage of animals. In humans the embryo begins to develop about four days after an egg is fertilized. Appearing initially as a tiny mass of cells, it eventually gives rise to the fetus, an obvious human form. In the first days of the embryo's existence, it journeys along the fallopian tube Embryo Day 3: Cells have continued dividing and embryos are between 6-8 cells. (Middle left) According to the Pacific Centre for Reproductive Medicine, up until this point, the maternal DNA has been contributing to embryo development. At some point on day 3 the paternal DNA kicks in. Morula Day 4 Fetal Development Stages Of Baby Growth In The Womb. It has now moved down the fallopian tube and implanted itself into the lining of your uterus. as your baby continues to grow, it becomes an embryo. an embryo is made up of 3 tissue layers. the inner layer will be your baby's lungs, liver, and digestive system. the middle layer will become your baby's bones, kidneys, sex organs, and heart

File:Stage16 bf5

In the first stages of embryonic development, a single-celled zygote undergoes many rapid cell divisions, called cleavage, to form a blastula, which looks similar to a ball of cells. Next, the cells in a blastula-stage embryo start rearranging themselves into layers in a process called gastrulation Both mouse and human germline cells appear to reset their biological age in the early stages of an embryo's development. A rejuvenation period that takes place after an embryo has attached to.

the embryo is the mutlicellular diploid eukaryote in one of the early stages of development. The eukaryote is termed as the embryo, in humans, 8 weeks past the fertilization. Embryo refers to that stage in the developing process of the organism which starts from the initiation of the first cell division till the birth (till hatching in. Figure 10. Stages of development in an angiosperm the embryo upto dormancy. B. MORPHOGENETIC CHANGES. 1. Establishment of body plan. 2. Establishment of meristems 3. Establishment of food reserves; Dormancy 1. Establishment of body plan. Two developmental patterns have been identified a) Shoot-root axis determination Embryos of various stages are illustrated in Figures 14 to 25. The first three divisions of the embryo are called cleavage divisions; thus, one-to eight-cell embryos are defined as cleavage stages. During this time the embryo actually decreases in weight. Only at the morula stage does the embryo begin to weigh more than at the one-cell stage

During the embryonic stage of prenatal development, how many layers of cells eventually form every part of the human body? asked Apr 19, 2019 in Psychology by KerriG. A. 5 B. 3 C. 8 D. 10. developmental-psychology; 0 Answers. 0 votes. answered Apr 19, 2019 by sangjoo. In the fifth week, the embryonic development stage transitions into the fetal stage, and the development of features such as toes, whisker buds and claws will form. The fetus begins to look more like a puppy every day. A veterinarian will be able to determine the gender and hear a fetal heartbeat at this stage. In the final few weeks of. The embryonic period of development is the stage in which most organs are formed. Organs begin to form, and the embryo elongates and starts to assume a human-like shape. The heart and main blood vessels are formed, and the heart starts beating by the 6th week. The primitive brain and spinal cord (neural tube) also begin to form

The microbial diversity and changes throughout the embryonic development stage of Macrobrachium rosenbergii were described., Figure 28.2.12 - Embryo at 7 Weeks: An embryo at the end of 7 weeks of development is only 10 mm in length, MI is the step preceding MII, his testicles begin to move from the abdomen into the scrotum, If your baby is a. The process of fertilization is tightly controlled to ensure that only one sperm fuses with one egg. After fertilization, the zygote undergoes cleavage to form the blastula.The blastula, which in some species is a hollow ball of cells, undergoes a process called gastrulation, in which the three germ layers form.. See full answer to your question here. Likewise, people ask, what are the 4. Choose from Human Embryo Development Stages stock illustrations from iStock. Find high-quality royalty-free vector images that you won't find anywhere else After two days of static culture from E6.5, early somite-stage embryos (E8.5) were transferred into the roller culture protocol, which allowed normal development of embryos isolated at early.

Timeline human development - Embryolog

The journey of embryonic development starts at oocyte fertilization, which triggers a complex cascade of events and cellular pathways that guide early embryogenesis. Recent technological advances have greatly expanded our knowledge of cleavage-stage embryo development, which is characterized by an increased rate of whole-chromosome losses and gains, mixoploidy, and atypical cleavage. Animal Development Campbell's Biology Ch 43 - 4th ed./Ch 47 - 6th ed Hox Genes Homeotic or homeobox genes are master genes that control expression of genes responsible for specific anatomical structures Ex: the place legs here instructions in a developing embryo Fertilization Many steps have been studied in the sea urchin, an echinoderm Acrosome Reaction Acrosome at head of a sperm. after conception. The developing ball of cells is now called an embryo. In this stage, all the major organs form, and the embryo becomes very fragile. At the end of the embryonic period, the embryo is only about an inch long. Stage 3: The Foetal Stage The last stage of prenatal development is the foetal stage, which lasts from two months after.

Candled Russian Tortoise Egg - estimated about 3 weeks

At 3 weeks the embryonic length has increased to about 1.5-2 mm. The measurements at later stages are shown in figure 0-3. Page 6. Fig. 0-3. The length of the embryo from stage 8 to stage 23, approximately 2½to 8 postovulatory weeks, based on the measurements of more than 100 specimens that had been graded as excellent in quality After the third month of pregnancy, the embryonic stage is over and the fetal stage begins, so the embryo is now called fetus. The baby-to-be already has all the organs but they are still developing. Further growth is necessary for them to be considered fully developed. During this month, the male or female genitals are formed as well EMBRYONIC DEVELOPMENT • During the third week of pregnancy, amniotic sac begins to form around the embryo. * Amniotic Sac-a thin membrane forming a closed sac about the embryos or fetuses of mammals and containing amniotic fluid. * Amniotic Fluid-the serous fluid in which the embryo or fetus is suspended within the amnion The objective of that work is to describe the anatomy of the development of three stages of the embryology of Coffea arábica var. típica (serial bud (1), final dormant stage (3), and the blossom.

Table 14.1 connects the different stages of development to the adult structures of the CNS. One other benefit of considering embryonic development is that certain connections are more obvious because of how these adult structures are related. The retina, which began as part of the diencephalon, is primarily connected to the diencephalon developing organism between fertilization and birth or hatching is called an embryo. The developmental process of an embryo is called embryogenesis, which can be divided into several stages. The first embryonic stage immediately following fertilization is called cleavage, which is characterized by rapid mitotic division of the fertilized egg

IVF embryo quality and day 3 embryo grading after in vitro fertilization Cleavage stage embryo grading Embryo picture of a perfect looking 8-cell embryo (day 3 embryo) There is no embryo fragmentation and the cells are very even, regular, and similarly size Schematically, three implantation stages can be distinguished:·. Adplantation of the blastocyst on the endometrium. Adhesion of the blastocyst to the endometrium. Invasion of the trophoblast and embedding. Adplantation of the blastocyst on the uterine mucosa. When the blastocyst emerges from the pellucid zone on the 5th day ( 3 ), it comes.

Embryology: Pre-Embryologic Stage (Weeks 1-3) Medical

Development of the embryo This stage is characterized by the formation of most of the internal organs and external structures of the baby's body. Most organs begin to form about 3 weeks after fertilization, which is equivalent to 5 weeks of pregnancy (because doctors date the pregnancy from the first day of the woman's last menstrual period. during neural development (week 3-4) of the embryonic stage: other 5th step: ventral cells of the caudal neural tube are called ___ and form the ___ part of the spinal cord. Basal plate Motor. At 5th week (embryonic stage), embryonic brain divides into three segments. Prosencephalon (forebrain Table 3 6Various Stages of Embryo Development in Chickens Embryo Drawing Cross-Section Drawing Descriptions 18-hour wm* sec 18-hour cross-section - Appearance of alimentary tract Cannot find 38-48-hour wm sec 33-hour cross-section - Visible cardinal veins - Well-developed vessels Cannot find 60-70-hour wm sec 72-hour cross-section.

Fetal development: Month-By-Month Stages of Pregnanc

Prenatal development has into two stages, the embryonic stage that comprises the first eight weeks of development after fertilization, and the fetal stage that encompasses the remainder of development. The embryonic stage is the period when body plans are laid out, and the precursors of what will become organ systems are determined Stage 3 embryos are called free blastocysts. They have an estimated postfertilization age in vivo of between four and five days and measure 0.1 to 0.2 mm in diameter. During Stage 3 the embryo separates into outer trophoblast cells and inner embryoblasts (inner cell mass) that will develop into the embryo proper

What Are the Stages of Fetal Development? (with pictures

The diagram below represents early stages of embryo development. Which term is best matche tal of 42 stages in embryo development, with organogenesis (formation of organs) and the development of a body plan taking place in the first 33 stages 1. This is when the brain and digestive system are formed, the skeletal system is calcified, and feathers develop. The last few stages are more specie Limb development of the axolotl is very at 18°C after 64 days of development (Fig. much retarded compared to A. 3). The hind limbs of the axolotl larva are maculatum. Forelimb development of the well developed with toes after 84 days stage 40 axolotl compares to that of the development (Fig. 3)

Development of the lower respiratory tract begins on day 22 and continues to form the trachea, lungs, bronchi, and alveoli. The process divides into five stages: embryonic, pseudoglandular, canalicular, saccular, and alveolar stage. Although the process begins early on in fetal development, complete maturation does not take place until the child is approximately 8 years of age Select a stage name below to get a detailed description and images. You can also browse the zebrafish Anatomical Ontology (AO) to show anatomical terms that are present at that stage. (h = hours of development at 28.5°C Follow Us: The three stages of prenatal development are the germinal stage, the embryonic stage and the fetal stage. These stages begin two weeks after conception. Prenatal development takes about 38 weeks to complete and goes through these three developmental stages. The first stage is the germinal stage Cleavage stage embryo. Assessment of the cleavage stage embryo by using morphological characteristics is multivariate and complex. Percentage and localization of fragmentation, evenness of the blastomeres, multinucleation and speed of cleavage are the most widely examined features to evaluate the quality of a cleavage stage embryo on Day 2 and Day 3 Mark Jones Writing Assignment 3/5/2017 During the early stages of embryo development, a multitude of signals are being released, some of which specify a cell, such as the neural plate, somites, and notochord, to a dorsal fate

Embryo development until blastocyst stage with and without renewal of single medium on day 3. Peña F(1), Dávalos R(1), Rechkemmer A(1), Ascenzo A(1), Gonzales M(2). Author information: (1)Laboratorio de Reproducción Asistida, Clínica Miraflores, Lima, Peru You can visit the Virtual Human Embryo project at the Endowment for Human Development site to step through an interactive that shows the stages of embryo development, including micrographs and rotating 3-D images.. Intrinsic vs extrinsic factors in cell specialization. The information below was adapted from Khan Academy Introduction to development Below is the description of the stages of embryonic development of Alligatoridae M. niger, based on the main external morphological traits starting from the tenth day of oviposition. Stage 4 (10-day old embryo): Approximately 26 pairs of somites are visible on the dorsum of the embryo. The mandibular arch is the largest of the three pharyngea embryonic stage. 2 weeks to the end of month 2. embryonic stage. all vital organs are being formed. embryonic stage. heart beats. 3 Stages of Prenatal Development. 22 terms. Life-Span Development Chapter 3- Prenatal Development and Birth. 12 terms. CH-3 Prenatal Development & Birth. 21 terms

By the end of the embryonic period, the embryo is approximately 3 cm (1.2 in) from crown to rump and weighs approximately 8 g (0.25 oz). Figure 28.15 Embryo at 7 Weeks An embryo at the end of 7 weeks of development is only 10 mm in length, but its developing eyes, limb buds, and tail are already visible In every pregnancy, a woman starts out with a 3-5% chance of having a baby with a birth defect. This is called her background risk. This fact sheet talks about the critical periods of development and types of birth defects that can result from exposures at different stages of pregnancy Figure 18.1. 1: The stages of embryogenesis in eudicots. I. The developing seed contains the triploid endosperm (1) and the diploid zygote (2). II. The zygote divides, forming the proembryo (3), which is anchored to the micropyle by suspensor (4), which has a large basal cell. The endosperm has also divided Accordingly, auxin distribution changes dynamically at key steps of embryo development (Friml et al., 2003). After the first division of the zygote, apical cell development requires PAT (Friml et al., 2003). At this stage, auxin is locally produced in the cells of the suspensor (Robert et al., 2013) Fetal Development: Stages of Growth Within 24 hours after fertilization, the ball of cells is called an embryo. • 1The embryo grows to a length of 0.2 mm (about / 100 inch), There are three major stages of gestation: Pre-embryonic stage - From fertilization to week two of development when a fertilized egg develops into a blastocyst.

23.3: Embryonic Stage - Biology LibreText

Mar 31, 2014 - Have you ever wanted to know more about the stages of #embryo development? Our #embryology lab has shared beautiful pictures of embryos at different stages. See more ideas about ivf, infertility, beautiful pictures A recent reference guide maps the stages of heart development onto the HH-stage series [18]. In addition, the series has been refined for the stages of gastrulation [19], which starts with the formation of the primitive streak in the midline of the embryo. In the early chick gastrula (Hamburger-Hamilton, HH stage 3), cardiac progenitors are. 3 day old human embryo (8 cell stage) manipulation of human blastula embryo Sumanas, Inc. animation - Human embryonic stem cells Embryogenesis & Germ Cell Layers 4. Gastrulation - period of cell migrations around blastopore (an organizer), which converts embryo from hollow ball of cells into a 3 layered stage called gastrula embryo* & pi

Chick Embryo DevelopmentCandling Photos and Movie Clips | Nebraska Extension in

Most silkworm strains exhibit embryonic diapause, which is a form of developmental arrest at the initial elongation stage, for winter dormancy. However, nondiapausing strains, such as pigmented nondiapause 1 (pnd-1), are often used for early embryogenesis study so that continuous observation of the early embryogenesis process is possible Comments. Mouse embryos can be staged according to a variety of criteria, the most general of which are those described by Theiler in The House Mouse: Atlas of Mouse Development (Springer-Verlag, New York, 1989).Theiler's criteria are too broad to distinguish many of the important phases of early development and must therefore be supplemented by others, for example, cell number, somite. Once the embryo is fully formed, it expands, grows, and continues to develop in what is known as the fetal development stage. This is when the mother becomes physically enlarged and visibly pregnant Part 1: Stages of human life during pregnancy from. before. conception to a two-week old embryo: The following information is approximate & intended for general information. Every pregnancy is different. Development varies from fetus to fetus. Do not rely on this information for personal medical decisions The stages of pregnancy are described in three trimesters, with a fourth trimester after birth. A developing baby is called an embryo from the moment conception takes place until the eighth.