Reproductive system

List the stages of development from secondary oocyte to birth. Also indicate where each of these stages are located.

- sperm and egg combine to make a unique cell called a zygote - this cell has all the information needed to divide, multiply, & develop into an embryo - each day the cells continue to divide, creating more cells - now the embryo is on a path, dividing & moving away from the ovary & along a uterine tube. It takes about 5 days to reach the uterus. By that time the fertilized egg has become a collection of hundreds of cells, called a blastocyst.

Prolactin

- weeks 20-40 - secreted by anterior pituitary gland - responsible for milk production, & rises throughout pregnancy to prep for nourishment for baby

Estrogen

- weeks 20-40 - secreted by corpus luteum and placenta - helps uterus grow and increase blood placenta

Progesterone

- weeks 20-40 - secreted by corpus luteum and placenta - keeps placenta functioning properly

human chorionic gonadotropin (hCG) hormone

-Weeks 1-20 - first secreted by cells that will form chorion later in pregnancy and later by blastocytes - maintains corups luteum to continue secreting estrogen and progesterone - by the end of the 2nd week of development, hCG is usually detected in urine, meaning preganancy - after 1st 3 months, hCG taper off as corpus luteum degenerates because placenta is now producing estrogen and progesterone

how many chromosomes are found in sperm and eggs?

23

how many chromosomes in a zygote?

46

How many days does it take the embryo to reach the uterus?

5 days

How many weeks old is the developing embryo when sex determination begins?

8th week

morula

before zygote implants on uterine wall, name of fertilized oocyte before it becomes a blastocyst (continues to divide and multiply cells)

As the baby moves toward the birth canal, the ______________________________ dilates.

cervix

When the embryo implants in the uterine wall it has ______________________________ of cells and is called a ______________________________.

cluster, blastocyst

term for the time of fertilization, marking the beginning of pregnancy

conception

What is the first event of labor?

contractions

Fraternal (dizygotic) twins

develop when two oocytes are released at the same time. Each oocyte is fertilized and both embryos implant, but they develop separate placentas, chorions, and amniotic sacs. Fraternal twins are as genetically alike as any other pair of siblings.

Each sperm carries

either an X or a Y chromosome (along with 22 other chromosomes)

As soon as the genetic information on the chromosomes from the two parents merges into one nucleus in the zygote, it divides. Once it begins dividing it is called an _________.

embryo

When the male and female sex cells unite they form a ___________, which develops into an __________ and later into a ___________. These events occur after an embryo implants in the uterus are called _________.

fertilized egg (zygote), embryo, fetus, pregnany

Zygote

fertilized oocyte (egg), when sperm & egg combine & make a fertilized oocyte (newly fertilized oocyte)

Which of the above stages is fertilized by a sperm and where?

fertilizes secondary oocyte in the ovary

What is the role of the amnion?

forms sack that will fill fluid to cushion the developing embryo

What part of the sperm contains the chromosomes?

in the head of the sperm within nucleus

oocytes can carry

only 23 chromosomes

During pregnancy and labor, the uterus, the placenta, and the growth of breasts are maintained and controlled by

oxytocin

These contractions are regulated by what hormone?

oxytocin

After the baby is delivered, contractions expel the ______________________________.

placenta

reproductive system purpose

produce offspring and pass genetic info from one generation to the next

Identical (monozygotic) twins

s develop from a single zygote that splits in half at some point during development. They usually share a placenta and a chorion. Rarely, identical twins will share amniotic sacs.

What hormone dominates the development of sex organs if the embryo carries a Y chromosome?

testosterone

The neural tube becomes

the brain and the spinal cord

The sex of the baby (boy or girl) is determined by

the sperm, since it has X & Y chromosomes

zona pellucida (innermost) zona radiata (outermost)

these layers support and protect the oocyte and zygote during early development

path of sperm cells from their release inside the vagina to the upper uterine tube where they meet unfertilized oocytes

vagina -> cervix -> uterus -> uterine tube

At how many weeks of pregnancy does the embryo become a fetus?

week 9

blastocyst

when fertilized oocyte/ zygote becomes a cluster of cells that is implanted in the endometrium layer of uterine wall

What is the role of the yolk sac?

will become part of the digestive tract

What is the role of the developing placenta and umbilical cord?

will enable embryo to take in nutrients and eliminate waste

Two outer layers that surround oocyte and the zygote

zona pellucida (innermost) zona radiata (outermost)

path of the zygote from the site of conception to the site of implantation

zygote travels from the uterine tube into the uterus. It develops into a morula and then a blastocyst before implanting into endometrium of uterine wall