Embryonic development days

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Human reproduction can be divided in several stages: formation of gametes(gametogénesis)fertilisation or unión of gametes and the development of the embryo(gestation,birth).DNA=23 chromosones.

OVARIAN CYCLE: 1-14-->folicular phase(developed due FSH)

-14-->ovulation(reléase of a mature ovum due to LH).

15-28-->secretory phase(corpus luteum is produced and secretes progesterone)

UTERINE/MENSTRUAL CYCLES: 1-5-->menstruation; endometrium comes off and is expelled with blood.

5-14-->proliferature: endometrium is built up due to estrogens.

15-28-->secretory phase; endometrium reaches its máximum thickness and prepares to recieve the embryo. 

GESTATION: during the first weeks the cell mas is refered as embryo, when it have a human shape we call it fetus. 3stages:

-Germinal: zygote transforms into a cell mass call morula, that creates blástula.

-Embryonic: 3 layers are formed from blastula; inner(endoderm),middle(mesoderm),outer(ectoderm).

-Fetal: all body structures are formed, embryo becomes a fetus.

BIRTH: normaly takes around 40th week of gestation; release of mucus plug indicates.Three stages:

-Dilation of the cervix: while cervix dilates, the myometrium experiences a serie of contractions that become frecuent and more intense. Amnion ruptures releasing amniotic fluid; breaking waters.

-Fetus release: fetus pushes its head out first; if not works is needed a cesarian section.

-Delivery of the placenta: After the baby is born, the uterus suffers more contractions in order to release the placenta.



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