vastatkaa pian

mistä ihmeestä alkio saa verensä, koska sillä ei todellakaan ole omaa verenkiertoa, eikä hengitä itse.

selittää kirjoitti:

mistä ihmeestä alkio saa verensä, koska sillä ei todellakaan ole omaa verenkiertoa, eikä hengitä itse.

^Sehän on alkio vielä tuossa vaiheessa, eikä tarvitse kumpaakaan heti. Sitten kun se saapuu kohtuu ja aloittaa kiinnittymisen alkaa vasta rakennusprosessi joka yhdistää odottavan naisen ja alkion.

selittää kirjoitti:

mistä ihmeestä alkio saa verensä, koska sillä ei todellakaan ole omaa verenkiertoa, eikä hengitä itse.

Alkio on ennen kiinnittymistään "solumassa", siis köntti soluja. Munasolussa on ravinteita niin paljon, että nämä solut selviää ja pystyvät jakautumaan ennen kiinnittymistään.

http://www.nlm.nih.gov/medlineplus/ency/article/002398.htm :

When sperm is deposited in the vagina, it travels through the cervix and into the Fallopian tubes.

ZYGOTE

A single sperm penetrates the mother's egg cell, and the resulting cell is called a zygote. The zygote contains all of the genetic information (DNA) necessary to become a child. Half of the genetic information comes from the mother’s egg and half from the father’s sperm. The zygote spends the next few days traveling down the Fallopian tube and divides to form a ball of cells.

BLASTOCYST

The zygot continues to divide, creating an inner group of cells with an outer shell. This stage is called a blastocyst. The inner group of cells will become the embryo, while the outer group of cells will become the membranes that nourish and protect it.

The blastocyst reaches the womb (uterus) around day 5, and implants into the uterine wall on about day 6. At this point in the mother's menstrual cycle, the lining of the uterus has grown and is ready to support a fetus. The blastocyst sticks tightly to the lining, where it receives nourishment via the mother's bloodstream.

EMBRYO

The cells of the embryo now multiply and begin to take on specific functions. This process is called differentiation. It leads to the various cell types that make up a human being (such as blood cells, kidney cells, and nerve cells).

There is rapid growth, and the baby's main external features begin to take form. It is during this critical period (most of the first trimester) that the growing baby is most susceptible to damage. The following can interfere with the baby's development:

* Alcohol, certain prescription and recreational drugs, and other substances that cause birth defects
* Infection (such as rubella or cytomegalovirus)
* Nutritional deficiencies
* X-rays or radiation therapy

WEEK BY WEEK CHANGES

The following list describes specific changes that occur in the womb:

* Week 3 of gestation
o The brain, spinal cord, and heart begin to develop
o The gastrointestinal tract begins to develop
* Weeks 4 to 5
o Arm and leg buds become visible
o Brain develops into five areas and some cranial nerves are visible
o Eyes and ear structures begin to form
o Formation of tissue that develops into the vertebra and some other bones
o Further development of the heart which now beats at a regular rhythm
o Movement of rudimentary blood through the main vessels
* Week 6
o Arms and legs have grown longer, and foot and hand areas can be distringuished
o Hands and feet have fingers and toes (digits), but may still be webbed
o Brain continues to form
o Lungs begin to form
* Week 7
o Nipples and hair follicles form
o Elbows and toes visible
o All essential organs have begun to form
* Week 8
o Eyelids are more developed
o External features of the ear begin to take their final shape
o Facial features continue to develop
o Intestines rotate

The end of the eighth week marks the end of the "embryonic period" and the beginning of the "fetal period".