Pregnancy.I need to know everything about pregnancy for my biology exam. But I'm stuck. I need to know some hormones produced, the stages ovulation-fertilisation-zygote-morula-blastula-implantation...


I need to know everything about pregnancy for my biology exam. But I'm stuck. I need to know some hormones produced, the stages ovulation-fertilisation-zygote-morula-blastula-implantation and the placenta. Please help.

Expert Answers
ako6777 eNotes educator| Certified Educator

During pregnancy many hormone levels increase.  Prolactin is increased.  This regulates lactation and during pregnancy it causes enlargement of the mammary glands.  The parathyroid hormone increases causing increases of calcium uptake in the gut and reabsorption by the kidney. Cortisol, aldosterone, and placental lactogen increase as well. 

The zygote is the initial cell formed during reproduction. A human zygote exists for about four days, and becomes a blasocyst on the fifth day. "In humans the morula develops and travels to the uterus around 3 to 4 days after fertilization, and at about 4 to 5 days after fertilization a fluid-filled space called the blastocoel cavity appears and the morula becomes a blastocyst."  Once a blastocyst the cells may adhere to the uterine wall and become implanted.

"The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination and gas exchange via the mother's blood supply."

In humans the placenta usually weighs about one pound and is dark reddish in color. It connects to the fetus by an umbilical cord that contains two arteries and one vein.

alexandria917 | Student

One hormone that is produced upon implantation is called human chorionic gonadotropin or hCG for short. It is the presence of this hormone that is tested for with home tests to determine whether or not a woman could be pregnant.


"All pregnancy tests work by detecting a certain hormone in the urine or blood that is only there when a woman is pregnant. This hormone is called human chorionic gonadotropin (kohr-ee-ON-ihk goh-NAD-uh-TROH-puhn), or hCG. It is also called the pregnancy hormone.

hCG is made when a fertilized egg implants in the uterus. This usually happens about six days after the egg and sperm merge. But studies show that in up to 10 percent of women, implantation does not occur until much later, after the first day of the missed period. The amount of hCG rapidly builds up in your body with each passing day you are pregnant."