What happens during the germinal stage?
The germinal period (about 14 days in length) lasts from conception to implantation of the zygote (fertilized egg) in the lining of the uterus. During this time, the organism begins cell division and growth. After the fourth doubling, differentiation of the cells begins to occur as well.
What development occurs in the germinal stage?
Processes in the Germinal Stage. The germinal stage involves several different processes that change an egg and sperm first into a zygote, and then into an embryo. The processes include fertilization, cleavage, blastulation, and implantation.
What are the 3 main stages of prenatal development?
This union marks the beginning of the prenatal period, which in humans encompasses three distinct stages: (1) the pre-embryonic stage, the first two weeks of development, which is a period of cell division and initial differentiation (cell maturation), (2) the embryonic period, or period of organogenesis, which lasts …
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 function of the Allantois?
allantois, an extra-embryonic membrane of reptiles, birds, and mammals arising as a pouch, or sac, from the hindgut. In reptiles and birds it expands greatly between two other membranes, the amnion and chorion, to serve as a temporary respiratory organ while its cavity stores fetal excretions.
During which stage of prenatal development is the morula formed?
The morula stage occurs 3-4 days after fertilization, just as the early embryo enters the uterus. 2. Soon the blastocystic cavity develops inside it (fluid-filled cavity).
What is a germinal stage?
What is the zygotic stage?
zygote, fertilized egg cell that results from the union of a female gamete (egg, or ovum) with a male gamete (sperm). In the embryonic development of humans and other animals, the zygote stage is brief and is followed by cleavage, when the single cell becomes subdivided into smaller cells.
What is the difference between amnion and allantois?
The key difference between amnion and allantois is that amnion is the innermost thin membrane that surrounds the developing embryo or fetus, forming a hydrostatic cushion, while allantois is an extension of the posterior wall of the yolk sac, and lies between the amnion and chorion.
When does the allantois develop?
The allantois starts to develop from about stage 18 (3 days), though in some individuals it may not appear until 4 days. Shortly after its appearance it forms a ramifying network of capillaries that receive blood via the allantoic (umbilical) arteries and return it to the body via the allantoic (umbilical) veins.
What is the correct order of stages of prenatal development?
There are three stages of prenatal development: the conception stage, the embryonic stage, and the fetal stage. Each stage of prenatal development is carried out over the course of approximately 40 weeks, which is the average length of most pregnancies. The conception stage is the shortest, and the fetal stage is the longest.
What are the correct sequence stages of prenatal development?
Stages of Prenatal Development Germinal Stage. The germinal stage begins at conception when the sperm and egg cell unite in one of the two fallopian tubes. Embryonic Stage. At this point, the mass of cells is now known as an embryo. Fetal Stage. Once cell differentiation is mostly complete, the embryo enters the next stage and becomes known as a fetus. A Word From Verywell.
What is the longest period of prenatal development?
The longest period of prenatal development is the fetal period which begins at the 9th week after conception and lasts until birth. By the 12th week, the genitals have formed. Development of all the structures of the body continues and by the end of the third month,…
What is the first phase of prenatal development?
In medical literature, prenatal development has three stages: germinal, embryonic and fetal stage. This first stage begins with the binding of the male and female sex cells, i.e. forming an egg cell, called zygote. The zygote will divide into two cells, then these two will divide into four, and so on.