Body systems develop. Limbs and facial features take shape. Around week 36 usually , the process of labor begins. In the first stage, dilation , hormones stimulate downward contractions of the uterine walls.
The contractions push the head of the fetus against the cervix at the lower end of the uterus. The cervix dilates.
In the second stage, expulsion , powerful contractions push the head and the rest of the body through the dilated cervix, and out through the vagina and the vulva.
The baby is born. Further contractions expel the placenta to complete the placental stage. Reproductive structures begin to form in the embryonic stage.
By week 6, gonads and genitalia are present but undifferentiated. Whether they become male or female is determined by one chromosome delivered by the sperm. This pair contains an X sex chromosome from the female egg and either an X or a Y sex chromosome from the male sperm. If the chromosome pair is XY, the gonads develop into testes starting in week 7. If the chromosome pair is XX, the gonads become ovaries starting in week 8. Testes secrete testosterone, forming male genitalia around week Without testosterone, female genitalia form.
All reproductive structures are in place at birth or shortly after. At puberty, an increase in sex hormones will grow them to their adult size and reproductive capability.
Download Reproductive System Lab Manual. See more from our free eBook library. An article in Science Daily on a research study that involves creating a synthetic model of the placenta to better understand pregnancy. Author: Healthwise Staff.
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It looks like your browser does not have JavaScript enabled. Please turn on JavaScript and try again. Important Phone Numbers. Top of the page. Topic Overview Most women are able to become pregnant from puberty , when their menstrual cycles begin, until menopause , when their cycles stop.
The sperm cells surround the egg cell if it is present. When a sperm enters an egg cell, they unite and their chromosomes mingle together. This is called conception or fertilization. If the egg is fertilized by the sperm cell, the fertilized egg cell begins to divide into two cells, then four, then eight, and so on, while it travels the rest of the way through the fallopian tube to the uterus.
There it implants and grows into the unborn baby. Skip to main content.
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