Hello and welcome to the zero to finals podcast.

My name is Tom and in this episode I'm going to be talking to you about the development of the embryo.

And if you want to follow along with written notes on this topic, you can find written notes at

zero definals.com slash embryo or in the reproductive system section of the zero definals

obstetrics and gynecology book. So let's get straight into it. A week after fertilization,

the implanted blastocyst starts to differentiate into various types of cell. The cells of the embryo blast split into two with the yolk sac on one side and the

amniotic cavity on the other.

The embryonic disc sits between the yolk sack on one side and the amniotic cavity on the other.

The cells of the embryonic disc develop into the fetal pole and eventually into the fetus.

The Corian surrounds this whole complex.

And the corian has two layers, the cytotrophoblast and the syncytferblast. The cytotrophoblast is the inner layer and the

syncytinaeotroflblast is the outer layer, which is embedded in the endometrium. Let's talk about some

basic embryology. Over a short time, a space called the corionic cavity forms around the yolk sac, embryonic

disc and the amniotic sac. These structures are suspended from the Corian by the connecting

stalk, which will eventually become the umbilical cord. At around five weeks gestation,

the embryonic disc develops into the fetal pole

containing three layers, the ectoderm, which is the outer layer, the mesoderm, which is the middle layer,

and the endoderm, which is the inner layer. These three layers go on to become all the different tissues in the body. The ectoderm becomes

the GI tract, the lungs, the liver, the pancreas, the thyroid gland and the reproductive system.

The mesoderm becomes the heart, muscles, bone, connective tissue, blood and the kidneys. And the ectoderm becomes the heart, muscles, bone, connective tissue, blood and the kidneys,

and the ectoderm becomes the skin, the hair, nails, teeth and the central nervous system.

At around six weeks gestation the fetal heart forms and starts to beat. The spinal cord and muscles

...