Embryology | Gametogenesis | Embryogenesis | Tetralogy & fertilization

Embryology is a branch of biology. Embryology was initiated by the famous Greek philosopher Aristotle who lived in 384–322 BC. Aristotle is regarded as the “Father of Embryology”. He was the first embryologist to describe the development and reproduction of many kinds of organism in his book titled “Degenerative Animalium”.

Aristotle firmly believed that the complex organisms develops from a simpler forms and laid the foundation for the basic principles of “epigenesis".

Embryology (from Greek ἔμβρυον, embryon, "the unborn, embryo"; and -λογία, -logia) is the branch of biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embryos and fetuses Embryology is the branch of biology that studies the prenatal development of gametes, fertilization, and development of embryos and fetuses. Additionally, embryology encompasses the study of congenital disorders that occur before birth, known as teratology. Embryology has a long history

There are different types or branches of embryology:


The descriptive embryology is defined as the study concerned with the direct observation and description of embryological development.


The comparative embryology is defined as the embryological development of different species is studied, analyzed and compared. Hence this paves way for understanding the evolution and phylogenetic significance.


The experimental embryology is defined as the embryos are experimented for studying the various developmental stages. Hence, it helps to understand the fundamental mechanisms of the organisms. In this field the embryos are dissected and the various parts of the embryo are removed, transplanted and even the environmental conditions are altered. It is also called as Casual Embryology or Analytical Embryology.


The chemical embryology deals with the biophysical, biochemical and physiological techniques. Hence it is also called Physiological or Biochemical Embryology.


The tetralogy is also a branch of embryology which deals with the malfunctions of the embryo.


The Developmental biology is the branch of biology which not only deals with the embryonic development but also the postanal processes such as the normal and neoplastic growth, metamorphosis, regeneration and tissue repair.

In eukaryotes, gametogenesis is the creation (genesis) of gametes (sperm in males and eggs in females). Gametogenesis creates these sex cells so that they are haploid, meaning they have half the DNA needed to make a new individual. Gametes fuse during the process of fertilization and eventually develop into an embryo.

Embryogenesis is the process by which an embryo forms and develops. For humans, the embryonic stage is from about 5-11 weeks (about 58 days) of development. In contrast, the embryonic stage for mice is about 16 days. Another difference between these two processes is that gametogenesis uses meiosis for cell division and embryogenesis uses mitosis.

Fertilization is the fusion of haploid gametes, egg and sperm, to form the diploid zygote. Note though there can be subtle differences in the fertilization process which occurs naturally within the body or through reproductive technologies outside the body, the overall product in both cases is a diploid zygote. Or Fertilization in humans occurs when a male sperm meets with a female egg to form a fertilized egg. This fertilized egg is called an embryo or a zygote

Where fertilization does occurs,

  1. · The Fallopian tubes is where most fertilization happens for normal pregnancies.

  2. · When a man and a woman engage in intercourse the man ejaculates semen into the vagina of the woman.

  3. · Up to 150 million sperm can be released in just one ejaculation of the man's semen.

  4. · The sperm set off to meet the egg in the Fallopian tube but they have to get there quickly as they will die between 12 to 48 hours of ovulation.

How fertilization does occurs?

  1. · The process as to "where human fertilization occurs" starts with a woman's menstrual cycle.

  2. · Menstrual cycle gets the woman's body ready and about half way through human fertilizations begins. The egg reaches ovulation and is released into the Fallopian tube where fertilization will take place.

  3. With only 15% of the sperm that are ejaculated are able to make it all the way to the egg.

  4. · The sperm follow the signals that are given by the cervix and the vagina and reach the opening of the uterus.

  5. · Then the sperm will make their way through the mucus of the cervix and move up the uterus lining.

  6. · The womb, or the uterus lining, is where you will find the baby growing after the egg or zygote has been fertilized.

  7. · Approximately 1,000 sperm that are left, they make their way to the uterus they also have to find the right Fallopian tube.

  8. · While there are two to choose from, the egg can only be found in one of them. If the sperm select the right tube it will find the egg.

The entire process, from ejaculation to finding the egg, only takes around 20 minutes.

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