A Guide to Embryology: Divisions, Importance, And Processes

A Guide to Embryology: Divisions, Importance, And Processes

Embryology is the study of the origin and the development of embryo till maturation.

In this branch of human anatomy we investigate the molecular, cellular, and structural factors which contribute to the formation of an organism, it is also called as developmental anatomy.

The study of embryo development helps us to gain knowledge for creating health care strategies for better reproductive outcomes.

Prenatal development includes repeated division of cells in the body which results in growth in size, complexity, the structural and functional differentiation of body.


General embryology

  • It is the study of development during pre-embryonic and embryonic periods (first 8 weeks after fertilization).
  • During this period, the single-celled zygote is converted by cell multiplication, migration and reorganization into a miniature form of an individual with various organs and organ systems of the body.

Systemic embryology

  • It is a detailed study of the formation of primordia and their structural and early functional organization into various organs and systems of the body.
  • It is further subdivided into the development of cardiovascular the system, digestive system, urinary system, genital system, etc.

Comparative embryology

  • It is the study of embryos in different species of animals.

Experimental embryology

  • It is for understanding the effects of certain drugs, environmental changes that are induced (exposure to radiation, stress) on the growth and development of embryos and foetuses of lower animals.’
  • The knowledge gained from these experiments can be used for avoiding the harmful effects of human development.
  • It is a vigorous and promising branch of embryology.


  • This is a branch of embryology that deals with abnormal embryonic and foetal development, i.e. congenital abnormalities or birth defects.


Normal development

  • This subject tells us how a single cell (the fertilized ovum, i.e. zygote) develops into a new-born, containing numerous tissues and organs.
  • Normal adult anatomy: This knowledge helps us to understand many complicated facts of adult anatomy like the location and relations of organs to one another.
  • Examples—on the location of the heart on the left side of the thoracic cavity, liver on the right side of the abdominal cavity and its closeness to the stomach.

Developmental abnormalities

  • Embryology helps us understand why some children are born with organs that are abnormal.
  • Appreciation of the factors responsible for abnormal development assists us in preventing or treating such abnormalities.
  • Examples—exposure to radiation during pregnancy, use of certain medications during pregnancy or a genetic abnormality that exists in the family.

Understanding postnatal and adulthood diseases

  • The mechanisms (molecular and cellular) taking place during the development of embryo play a key role in the development of a wide range of diseases in adult life.
  • Examples—that can vary from the absence of an ear or presence of an extra finger to hypertension, diabetes, depression, cardiovascular and renal diseases.
  • This is known as foetal programming of adult diseases.

Health care strategies for the better reproductive outcome

  • Knowledge of embryology facilitates interpretation of the results of various techniques like foetal ultrasound, amniocentesis, and chorionic villous biopsy.
  • Based on the results, appropriate treatment can be planned.
  • Example—performing surgeries for correction of a defect in the diaphragm prenatally; postnatal correction of a cardiac defect; a medical line of management of a diabetic or hypertensive mother.

Therapeutic procedures for infertility/fertility-related problems

  • If the woman is unable to conceive by natural methods, alternate methods like cloning and in vitro fertilization can be planned.
  • For spacing the pregnancies, various birth control methods (medical and surgical) are available.
  • Basic knowledge of embryology is required for understanding the mechanism of action of these methods.

Stem cell therapy

  • Cells forming tissues in the embryo are called stem cells. These are undifferentiated cells that can differentiate into specialized cell types.
  • It is an uncommitted cell and depending on the signal it receives, it can develop into many specialized cells.
  • These cells are capable of treating certain diseases in postnatal life.

Basic Process in Embryology

Cell division

  • Mitotic division
  • Meiotic division


  • Number of cells
  • Size of cells
  • Intercellular substance


  • Histogenesis

Frequently Asked Questions (FAQs)

What are the 4 stages of embryology?

Embryology involves four phases which are fertilization, cleavage, gastrulation, and organogenesis. Fertilization occurs when the sperm and egg unite, leading to the creation of a zygote. The zygote divides rapidly into many cells during cleavage, forming a multicellular organism. Gastrulation is when the three germ layers are formed, which will give rise to different organs. During organogenesis, specific organs are formed through differentiation and development from the germ layers.

What is embryonic division?

Embryonic division, also known as cleavage, is the process of rapid cell division that occurs after fertilization in the early stages of embryonic development. During this process, the zygote divides into multiple cells called blastomeres. As the blastomeres divide, they form a solid ball of cells called a morula, which then undergoes further cell division and rearrangement to form a blastula. Embryonic division is critical to the formation of a multicellular organism and the establishment of the body plan.

What is embryology and why is it important?

Embryology is the branch of biology that studies the development of embryos from fertilization to birth or hatching. It is an important field of study as it helps us to understand the processes and mechanisms involved in the formation and growth of an organism. Embryology provides insights into the molecular and cellular mechanisms that underlie normal and abnormal development, which can be applied to the diagnosis and treatment of various developmental disorders. Additionally, embryology is essential to fields such as reproductive medicine, genetics, and evolutionary biology.

What is an example of embryology?

An example of embryology is the study of the development of the human nervous system. During embryonic development, the neural plate forms, which eventually folds and fuses to create the neural tube. The neural tube then differentiates into different regions that give rise to the brain and spinal cord. Understanding the molecular and cellular mechanisms involved in this process can help to explain how the nervous system develops and how it can go wrong in certain disorders, such as neural tube defects. Additionally, research in embryology has led to advances in the field of regenerative medicine, as scientists study how to regenerate damaged or diseased tissues and organs based on embryonic development processes.

What are the three layers of embryology?

The three layers of embryology are the ectoderm, mesoderm, and endoderm. These layers form during gastrulation, which is a key stage of embryonic development. The ectoderm gives rise to structures such as the skin, hair, nails, and nervous system. The mesoderm gives rise to structures such as muscles, bones, cartilage, blood vessels, and the urogenital system. The endoderm gives rise to structures such as the lining of the respiratory tract, gastrointestinal tract, and associated organs such as the liver and pancreas. The three germ layers are essential for the development of a wide range of tissues and organs in the body.

What is the size of embryo?

The size of an embryo can vary depending on the stage of development. Shortly after fertilization, the zygote is typically about 0.1-0.2 mm in diameter. By the end of the first week, the embryo has grown to about 0.2-0.3 mm in diameter and has formed a solid ball of cells called a morula. By the end of the second week, the embryo has grown to about 1-2 mm in length and has formed a structure called the blastocyst. By the end of the third week, the embryo has grown to about 2-3 mm in length and has formed the three germ layers. 

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