What are the stages of the embryonic period?
The process of prenatal development occurs in three main stages. The first two weeks after conception are known as the germinal stage, the third through the eighth week is known as the embryonic period, and the time from the ninth week until birth is known as the fetal period.
What is the first stage in embryonic development?
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.
What happens in the blastocyst stage?
It is at the blastocyst stage of development (five days after fertilisation) that an embryo would normally move out of the fallopian tube and into the uterus. Once in the uterus, the blastocyst starts to attach to the uterine lining in a process known as implantation.
What is the blastocyst stage of development?
In humans, blastocyst formation begins about 5 days after fertilization when a fluid-filled cavity opens up in the morula, the early embryonic stage of a ball of 16 cells. The blastocyst has a diameter of about 0.1–0.2 mm and comprises 200–300 cells following rapid cleavage (cell division).
What is blastocyst development?
blastocyst, a distinctive stage of a mammalian embryo. It is a form of blastula that develops from a berrylike cluster of cells, the morula. A cavity appears in the morula between the cells of the inner cell mass and the enveloping layer. This cavity becomes filled with fluid.
What is the blastula stage of embryonic development?
Blastulation is the stage in early animal embryonic development that produces the blastula. The blastula (from Greek βλαστός (blastos meaning sprout)) is a hollow sphere of cells (blastomeres) surrounding an inner fluid-filled cavity (the blastocoel).
What is a blastocyst?
By the fifth or sixth day, the fertilized egg is known as a blastocyst — a rapidly dividing ball of cells. The inner group of cells will become the embryo. The outer group will become the cells that nourish and protect it.
What is the earliest stage in embryonic stages?
Early Embryonic Development Cleavage and Blastula Stage. (a) During cleavage, the zygote rapidly divides into multiple cells without increasing in size. Gastrulation. The typical blastula is a ball of cells. The next stage in embryonic development is the formation of the body plan. Organogenesis. Organs form from the germ layers through the process of differentiation.
What is the earliest stage of an embryo?
An embryo is an early stage of development of a multicellular diploid eukaryotic organism. In general, in organisms that reproduce sexually, an embryo develops from a zygote, the single cell resulting from the fertilization of the female egg cell by the male sperm cell.
What are the stages of an embryo from conception to birth?
Stages of Baby Development From Conception to Birth Conception. Out of hundreds of eggs and millions of sperm, one egg and one sperm unite at conception. First Trimester. In the first four weeks from conception, fetal growth of the ovum begins with development of the spinal cord, nervous system, gastrointestinal system, heart and lungs. Second Trimester. Third Trimester. Birth.
What are the three stages of development?
The three stages of stream development are youthful, mature and old age. Each stage occurs in different locations and features specific characteristics. The first stage of stream development is youthful.