Prenatal development

The prenatal development or antenatal is the process in which an embryo or fetus , human is gestated during pregnancy , from fertilization until birth . Frequently, the terms fetal development or embryology are used in a similar sense.

After fertilization, the process of embryogenesis begins (the early stages of prenatal development). At the end of the tenth week of gestation the embryo has acquired its basic form and the next period is that of fetal development, when the organs are fully developed. 1 This fetal stage is described both topically (by organ) and chronologically (by time), with the main events being shown during gestational age.

Fertilization and implantation

After sexual intercourse , only a spermatozoon can pass through the cell membrane of the ovule , and thus fertilize it , mixing its genetic load – from the man – from that of the ovum, – from the woman. The cell resulting from this process is called a zygote . The zygote contains all the necessary genetic information – DNA – for this new cell to evolve into a newborn child. The zygote uses the following days to move to the uterus , crossing the fallopian tube first , and dividing by the way.

The set of cells that has formed the zygote, is called blastocisto , or blastula , and is divided into two groups of cells; One, more external, and another more internal. The inner group will become the embryo , and outside, in the membrane that will protect and nourish during pregnancy .

The blastocyst reaches the uterus on the fifth day after fertilization, and implants into the uterine wall , which is already ready thanks to the woman’s menstrual cycle. The blastocyst attaches strongly to the uterine wall, and from there receives the nutrients it needs to continue its development, directly from the woman’s bloodstream.

Embryonic period

Main article: Human embryogenesis

The cells of the embryo, initially called totipotent stem cells , multiply rapidly, and begin to differentiate by functions, differences that will mark the different types of human cells (blood, kidney or nerve).

In the first quarter, called embryonic period , is when the more susceptible it is the developing embryo, potential damage – Alcohol , certain medications , drugs stimulants, infections , nutritional deficiencies , X – rays or radiation among others.

Week 3

  • The brain, heart and spinal cord begin to develop
  • The digestive tract begins to develop.

Weeks 4 to 5

  • Buds or sprouts of arms and legs become visible
  • The brain develops in 5 areas and some cranial nerves are visible
  • Development of eye and ear structures begins
  • Formation of the tissue to be converted into the vertebrae and some other bones
  • Later development of the heart that now beats at a regular pace
  • Movement of rudimentary blood through the larger vessels

Week 6

  • The arms and legs have lengthened and can distinguish the areas of the feet and hands
  • Hands and feet have fingers (digits), but may still be adhered by membranes
  • The brain continues to form
  • The formation of the lungs begins

Week 7

Embryo seven weeks, and ten millimeters, coming from an ectopic pregnancy still in the oviduct.
  • Se forman los pezones y folículos pilosos
  • Elbows and toes are visible
  • All the essential organs have begun to form.

Week 8

Nine-week embryo, from an ectopic pregnancy in a fallopian tube.
  • Eyelids are more developed
  • The external characteristics of the ear begin to take its final shape.
  • Continued development of facial features
  • The intestines rotate.

Fetal Development

This stage begins from the moment the embryonic stage is completed, and until the birth occurs . During fetal life no new organs or tissues are formed , but the maturation of existing ones is produced.

Weeks 9 to 12

  • The eyelids close and do not reopen almost until the 28th week
  • The face is well formed
  • The limbs are long and thin
  • Genitalia appear well differentiated
  • Red blood cells are produced in the liver
  • The size of the head corresponds to almost half the size of the fetus
  • The fetus can hold its fingers
  • Dental outbreaks appear

Week 20

  • The lanugo covers the whole body
  • Eyebrows and eyelashes appear
  • Nails appear on feet and hands
  • The fetus is more active with greater muscle development
  • The woman can feel the fetus moving
  • Fetal heartbeats can be heard

Week 24

  • Eyebrows and eyelashes are well formed
  • All parts of the eye are developed
  • The fetus presents the prehensile and startling reflex
  • Traces of plantar skin and palmar skin begin to form
  • The pulmonary alveoli are formed

Weeks 25 to 28

  • Rapid brain development
  • The nervous system is sufficiently developed to control some bodily functions
  • Eyelids open and close
  • The respiratory system, although immature, has developed to the point of allowing gas exchange

Weeks 29 to 32

  • There is a rapid increase in the amount of body fat
  • Se presentan movimientos respiratorios rítmicos, pero los pulmones no están totalmente maduros
  • The bones are fully developed, but are still soft and flexible
  • The body of the fetus begins to store iron, calcium and phosphorus

Week 36

  • The lanugo begins to disappear
  • There is an increase in body fat
  • Las uñas de las manos alcanzan las puntas de los dedos

Weeks 37 to 40

  • The lanugo disappears except in the upper arms and shoulders
  • The nails of the hands extend beyond the tips of the fingers
  • Small buds or buds appear in both sexes
  • The hair on the head is now thicker, rougher, and greasier.

References

  1. Back to top↑ Westen, Drew (1999). Psychology, study guide: mind, brain and culture (in English) (Second edition). Hoboken NJ, United States: John Wiley and Sons, Inc.
  2. ↑ Jump to:a b c Images of 3D Pregnancy , consulted on August 27, 2007. It is also possible to have navigable 3D views.

Bibliography

  • TW Sadler, Langman (9th Edition, September 2004). Medical embryology with clinical orientation . Medical Publishing Panamericana, Madrid. ISBN 84-7903-865-9 .
  • Larsen, WJ (3rd Edition, 2003). Human embryology . Editorial Elselvier, Madrid. ISBN 0-443-06583-7 original edition .
  • This work contains a derivative translation of Prenatal development from Wikipedia in English, published by its editors under the GNU Free Documentation License and the Creative Commons Attribution-ShareAlike 3.0 Unported License .
  • Bottle Llusiá, José ; Lanchares, Juan Luis; Mora Teruel, Francisco (2000). The first two weeks of life . University of Salamanca. ISBN  9788478009619 .

External links

  • Wikimedia Commons has media related to Embryology .
  • Fetal development – for weeks – in MediLine Plus
  • Animation of human development, in AboutKidsHealth.ca (English)
  • The changes of the embryo in The Visible Embryo (English)

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  • Buds or sprouts of arms and legs become visible
  • The brain develops in 5 areas and some cranial nerves are visible
  • Development of eye and ear structures begins
  • Formation of the tissue to be converted into the vertebrae and some other bones
  • Later development of the heart that now beats at a regular pace
  • Movement of rudimentary blood through the larger vessels

Week 6

  • The arms and legs have lengthened and can distinguish the areas of the feet and hands
  • Hands and feet have fingers (digits), but may still be adhered by membranes
  • The brain continues to form
  • The formation of the lungs begins

Week 7

Embryo seven weeks, and ten millimeters, coming from an ectopic pregnancy still in the oviduct.
  • Se forman los pezones y folículos pilosos
  • Elbows and toes are visible
  • All the essential organs have begun to form.

Week 8

Nine-week embryo, from an ectopic pregnancy in a fallopian tube.
  • Eyelids are more developed
  • The external characteristics of the ear begin to take its final shape.
  • Continued development of facial features
  • The intestines rotate.

Fetal Development

This stage begins from the moment the embryonic stage is completed, and until the birth occurs . During fetal life no new organs or tissues are formed , but the maturation of existing ones is produced.

Weeks 9 to 12

  • The eyelids close and do not reopen almost until the 28th week
  • The face is well formed
  • The limbs are long and thin
  • Genitalia appear well differentiated
  • Red blood cells are produced in the liver
  • The size of the head corresponds to almost half the size of the fetus
  • The fetus can hold its fingers
  • Dental outbreaks appear

Week 20

[Fact: 18 weeks after fertilization.