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EMBRYOLOGY BASICS

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BASIC CONCEPTS 

All* the cells in our body have a nucleus.

The nucleus is a sac containing 46 X-shaped objects called cromosomes.

If you look at each cromosome veeery closely, you will see that each cromosome is made of little bricks called genes. Each gene is made of DNA, a special type of acid produced in the nucleus.

The difference in size of cromosomes means that they contain more or less genes.

Each gene contains the instructions on how to produce and assemble body parts.

In order to grow, all* the cells in our body must divide in 2 through a process called mitosis. Mitosis division results in 2 identical cells containing 46 cromosomes each.

 

*The exception are the gonads (ovaries and testicles) where cells do not divide in 2 identical cells, but in 2 halves each, containing 23 cromosomes. This division process is called meiosis.

Ovaries contain cells called “oocytes” or eggs. One oocyte contains 23 cromosomes.Testicles contain ‘spematozoids”. One spermatozoid contains 23 cromosomes.

 

When the oocyte and the sperm fuse (fertilization) a new cell (zygote) containing 46 cromosomes is formed. This cell divides through mitosis to form the newborn. Division continues throughout lifespan [One exception: mature nerve cells do not divide]

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EMBRYOLOGY 1 – FERTILIZATIONZYGOTE – MORULA – BLASTULA – BLASTOCYST (1-layer=1wk, 2-layers=2wk, 3-layers=3wk) – EMBRYO - FETUS

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EMBRYOLOGY 3 – 3 LAYER BLASTOCYSTFrom now on it’s an embryo

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EMBRYOLOGY 2 - IMPLANTATION

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EMBRYOLOGY 3 – 3 LAYERS OF EMBRYO

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EMBRYOLOGY 4 - ORGAN FORMATION

ECTODERM:   Nervous system and skinMESODERM: Muscles, bones, ligaments, tendons, heart, blood vessels, kidneys, and gonads.ENDODERM: Respiratory and digestive organs (i.e.: lungs, intestines, liver, gallbladder, pancreas, spleen)

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TERATOGENGreek for “monster forming”

Anything that can harm the baby during pregnancy

Remember: Most sensitive period of pregnancy is 1st trimester (exception: Herpes virus [3rd trimester & delivery])

Teratogens:• Common substances: Alcohol & tobacco• Toxic substances: Lead, mercury, arsenic, insecticides.• Microbes: ToRCHeS (Toxoplasm, Rubella, Chickenpox, 

Cytomegalovirus, Herpes, Syphillis).

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EXERCISES

The nucleus in like a containing (number) (shape) objects called

If you look at each veeery closely, you will see that each of them is made of little bricks called . Each is made of , a special type of acid produced in the nucleus.

The difference in size of cromosomes means that they contain more or less

Each contains the instructions on how to produce&assemble body parts.

In order to grow, the cells in our body must divide in 2 through:

All cells: division results in 2 cells containing cromosomes each.

Gonad cells: division results in 2 half-cells containing cromosomes each.

 

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Mention the stages of development from fertilization:O + S =Z M B B E F

How many layers does the blastocyst develop per week? What are the names of the layers of a 3-layer blastocyst?

Which organs develop from each layer?

What is a teratogen?Name 2 common teratogens, 2 toxic teratogens and 5 microbial teratogens.