Welcome to this lesson today on development, weeks one through eight. Today you will be talking about what happens as an embryo develops from one week through eight weeks of pregnancy.
During weeks one through eight the basic body plan of an embryo will began to develop. The first thing that happens is an embryonic disk will form and the embryonic disk is a thin disk of cells. It is essentially the first stage of setting up a body plan of the embryo. From there the neural tube will form within the embryonic disk and will actually become the brain and spinal cord. The cells that form into the neural tube originate from within the ecotderm; the inner layer of germ cells.
Following this other germ cell layers will also begin to specialize and give rise to certain body features, organs ,and organ systems. By the end of week eight, the embryo will actually begin to resemble a human being.
During weeks one through eight the reproductive structures will also begin to develop, depending on the inheritance of the sex chromosomes. Sex chromosomes are the chromosomes that determine the sex of the individual. If the individual inherited X and Y chromosomes, male reproductive structures will form. If the individual inherited X and X chromosomes, female reproductive structures will form.
At the end of week eight, the embryo is then called a fetus. It is considered an embryo prior to week eight and by the end of week eight it becomes a fetus.
During weeks one through eight there is always a chance a miscarriage can occur. Miscarriages can also occur later in development, although it's much less common. A miscarriage is when an embryo or fetus will be spontaneously expelled from the uterus. The cause or causes of miscarriage can be many factors but often times it is a genetic abnormality. As the body plan is being laid out and as the embryo is starting to develop into a fetus genetic abnormalities can cause improper development. The body, often times, will expel the abnormal fetus from the uterus because of these genetic abnormalities.
This lesson has been an overview on development of an embryo and a fetus from weeks one through eight. Specifically, this lesson focused on formation, reproductive structure development, and the possibilities of a miscarriage.
Keep up the learning and have a great day!
Source: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND
Part of the inner cell mass of the blastocyst, the embryonic disk is the cellular framework that begins embryonic development; the nervous system develops from ectoderm of this.
The developing baby after the first 8 weeks of development up to birth.
Also called spontaneous abortion, a miscarriage is when the embryo is expelled from the uterus.
A tube formed from the ectoderm of the blastocyst that serves as the framework for the development of the central nervous system (brain and spinal cord).
The X & Y chromosomes that when paired determine the gender of the child and carry other genetic traits as well; XX = female while XY = male.