What are the different stages of prenatal development?
There are three stages of prenatal development—germinal, embryonic, and fetal. Prenatal development is also organized into trimesters: the first trimester ends with the end of the embryonic stage, the second trimester ends at week 20, and the third trimester ends at birth.
Which stage of prenatal development is the period of most vulnerability?
As in the case of the germinal period, often the mother does not yet know that she is pregnant. It is during this stage that the major structures of the body are taking form making the embryonic period the time when the organism is most vulnerable to the greatest amount of damage if exposed to harmful substances.
What are the characteristics of prenatal period?
The fetus is characterized by fused eyelids and distinct human somatic characteristics. The fetal period covers gestational weeks 11 to 26. During the fetal period, the total body weight (TBW) increases from approximately 5 to 500 g. Fetal period precedes embryonal period, during which a viable fetus is delivered.
What happens to the embryos in stage 3 of development?
During Stage 3 the embryo separates into outer trophoblast cells and inner embryoblasts (inner cell mass) that will develop into the embryo proper. In vitro studies have shown that Stage 3 embryos go through four characteristic processes: 1) cavitation, 2) collapse/ expansion 3) hatching and 4) discarded cells.
What are the 5 stages of embryonic development?
Contents
- Germinal stage. 1.1 Fertilization. 1.2 Cleavage. 1.3 Blastulation. 1.4 Implantation. 1.5 Embryonic disc.
- Gastrulation.
- Neurulation.
- Development of organs and organ systems.
What is the germinal stage?
The germinal stage begins at conception when the sperm and egg cell unite in one of the two fallopian tubes. The fertilized egg is called a zygote. Just a few hours after conception, the single-celled zygote begins making a journey down the fallopian tube to the uterus.
What is the first stage in embryonic development?
Summary. The early stages of embryonic development begin with fertilization. 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.
Which is the correct order of embryonic stages?
Hence the correct answer is ‘C’ i.e, Zygote-morula-blastula-gastrula-embryo.
How does a human embryo develop?
First, the zygote becomes a solid ball of cells. Then it becomes a hollow ball of cells called a blastocyst. Inside the uterus, the blastocyst implants in the wall of the uterus, where it develops into an embryo attached to a placenta and surrounded by fluid-filled membranes.
In which Week C-section is safe?
Planned c-sections are usually done from week 39 of pregnancy because babies born earlier than this may not be fully developed for life outside the womb. You may have your c-section earlier than this if there’s a medical reason for delivering the baby sooner, for example, if you’re expecting more than one baby.