There is such an amazing and complex science that encompasses a series of long and evolutionary processes from the beginning of pregnancy to its end and that is . . Embryology Hello, welcome to my YouTube channel the title of this video is Introduction to Embryology Humana and the idea with this is to mention the basic concepts within human embryology in an extremely short and concise video for that we are going to start by answering the question What is embryology?
Etymologically, if we break down the word Embryology this would be the Study of the Embryo , however this term goes beyond that Embryology is the science that studies all the changes that occur in the formation of a new being from fertilization to birth and includes the study of the placenta and the extra-embryonic annexes the amnion, the yolk sac, the chorion, the allantois and the umbilical cord structures essential for normal development Embryology divides human prenatal development into three periods: a pre-embryonic period, an embryonic period and a fetal period This is a very good table, which summarizes in a simple way the prenatal development Everything begins on day 0, with fertilization, in which this new individual is formed called Egg Cell or Zygote This cell is the product of the union of a sperm with a type 2 oocyte and occurs in the distal third of the fallopian tube During the first week of gestation, this zygote It is called Blastocyst blasto means immature and cyst means cavity "an immature embryo with a cavity inside" The main biological process that occurs during the first week is Segmentation and it takes place in the fallopian tube or uterine tube This week includes the Pre-embryonic Period In the second week several changes occur at the intra-embryonic level The embryo is made up of two sheets, which is why we will call it a bilaminar embryo The most relevant biological process in implantation, where the embryo is introduced into the endometrium of the maternal uterus This week continues to constitute the pre-embryonic period In the third week a trilaminar embryo appears, the main event is Gastrulation and this embryo persists in the uterus with this week the pre-embryonic period ends Between the fourth and eighth week, the embryo obtains a cylindrical configuration, ceases to have a laminar configuration and the biological process The main logic is Organogenesis. All the outlines of the embryo's organs that will form the future systems are formed. The embryo is still in the uterus and these weeks are called the Embryonic Period From the ninth week of birth we speak of a fetus and the functional development of the outlines of the organs occurs and the body growth continues to remain in the uterus and we speak of a Fetal Period.
On the other hand, there is also the so-called Periods of Susceptibility or moments of alteration of development During this period, the devices and systems are more likely to be altered or that their alteration results in major malformations that sometimes make it incompatible with life The Embryonic Period is the period of greatest cell division and this results in cells being more susceptible to being altered by any external agent The normal development of an individual depends on two major factors one is Genetic Regulation having influence on the genetic plan that is established in DNA and the second is Epigenetic Regulation , that is, the influence of external factors that affect development During the entire embryonic development, there are five important processes known as Morphogenetic Mechanisms These mechanisms make it possible to achieve the characteristic shape of the embryo and the development of the outlines of most of the body's organs and these are: Induction, Cell Differentiation, Growth, Migration and Programmed Cell Death Induction is a process by which an embryonic tissue encourages another to change Cell differentiation is the biological process that leads to the formation of different classes of cells through an increase in morphological and functional complexity Growth is the increase in size and volume of the different parts and organs of the embryo Migration is the movement by which a group of cells r detaches from its site of origin and moves to another site And programmed cell death or apoptosis is a programmed phenomenon that produces ultra-structural changes in the cell, which lead to its destruction When studying embryonic development it is often necessary to know the relative location of the body's structures and from where and to where the changes are being made in the new being. For this in embryology we have what is called Position Terminology.