We continue our exciting journey through Pregnancy week after week, having stopped at week 4 and having attended the embryo implantation. We are located in week 5 of pregnancy, or week 3 of pregnancy (the duration of pregnancy is 40 weeks from the date of the last menstruation and 38 weeks from conception).
If you have not yet felt the first symptoms of pregnancy, you will probably start to notice them now, together with the absence of the period. Swelling and hypersensitivity of the breasts, nausea, desire to urinate frequently, tiredness and drowsiness ... are some of the signs that you are pregnant.
Confirm pregnancy
At this point the increase in estrogen, high levels of progesterone and the presence of the pregnancy hormone, human chorionic gonadotropin (hCG) are more evident in the body. Menstruation has not arrived, with a week of delay (in regular cycles) it is time to take the pregnancy test if you have not done so before.
There are women who notice pregnancy very early, instinctively according to some, or because of the symptoms and discomfort, but for others it may take a few weeks to notice these signs and the first thing they perceive is lack of rule.
If the pregnancy test confirms it, the time for go to the gynecologist to get the final confirmation, although for the early ultrasound in pregnancy that checks for embryo and if the implantation of this has occurred correctly it is usually done in week 6 of pregnancy, as we will see.
It is possible that inside, in the 5th week of pregnancy, the embryo will grow and is already in its third week.
Week 5 of pregnancy
This week the embryo is barely three weeks old (corresponding to the 5th week of pregnancy) and measures about one millimeter wide and four-five millimeters long. It already begins to have more differentiated parts in its characteristic "C" shape: the top and bottom, the left and the right, the front and the back are different.
At this stage in the embryo three differ germ layers or embryonic layers (blastodermal leaves), a set of cells formed during embryonic development from which the adult tissues and organs will originate.
The ectoderm is the outermost layer of cells surrounding the embryo: it forms the epidermis, the central and peripheral nervous system, the retina and other structures (hairs, nails, tooth enamel).
The endoderm is the innermost layer, which arises from the first and forms the epithelial coatings of the respiratory ducts and digestive tract, including the glands that flow into it. Also bladder, urethra, liver and pancreas.
The mesoderm originates through the process of mitosis of the ectoderm; It is a third layer of cells, located between the ectoderm and the endoderm. It includes smooth muscle layers, connective tissue, vessels that water tissues and organs, blood cells, part of the cardiovascular system, bone marrow and skeleton, striated muscles, and reproductive and excretory organs.
We are in the trilaminar period, which takes place in the third week of gestation. Towards the end of it, when the gastrulation process begins to end, some mesodermal cells will give rise to blood vessels inside the villi, thus forming the tertiary chorionic villi.
Soon these blood vessels will connect with the embryo circulation through the umbilical vessels, establishing the fetus-placental circulation: it is the beginning of the functioning of the cardiovascular system.
In the images of embryos of this gestational age more physical characteristics are already differentiated. On the back you can see a kind of crest that, when closed on itself, forms the neural tube.
This tube is the part of the embryo from which the brain and spine are formed and begins to form during the first month of pregnancy. Now the top of this tube is expanding and crushing to form the front part of the brain.
On both sides of the neural tube that runs through the back, tissue blocks called "somites" appear. From them will come the muscles and other body structures. The neural crest will give rise to numerous hundreds and important structures of the embryo: Schwann cells, meninges, melanocytes, adrenal gland marrow or bones.
In the center of the embryo appears a bulge that it will become the heart, and the first blood vessels begin to develop. The embryo is embedded between two protective membranes and constitutes the yolk sack, a balloon-shaped structure that is where the blood cells of the embryo are emerging.
Gradually, the embryo is taking shape, and its development is unstoppable. In the first trimester, and we'll see it throughout the next weeks of pregnancy, the advances in embryo growth are spectacular and, for most, mysterious and somewhat magical. We will tell you all about pregnancy week by week.
