All Flashcards
What is fertilization?
The Union of an egg cell and a sperm cell
What must the sperm cell do to reach the secondary oocyte?
Move upward through the uterus and uterine tube
What do prostaglandins in the semen do? What are prostaglandins?
Stimulate lashing of sperm tails
Lipids/ fats
What causes the oocyte cell membrane to prevent the entrance of more than one sperm?
the head portion of the sperm enters the oocyte, leaving the tail behind, triggering the oocyte cell membrane to release enzymes that hard the oocyte wall
What does the oocyte membrane do once one sperm head has entered the oocyte?
It releases enzymes that harden the oocyte wall, preventing any other sperm to enter
What is the fertilized egg now called?
A zygote
When does pregnancy begin?
When the developing offspring nestles into the lining of the uterus
How do fraternal twins form? Aka?
Two oocytes are released from the ovaries and fertilized
Fraternal aka dizygotic twins
How are identical twins formed? Aka?
Fertilization of a single oocyte which sprites into two cell masses
Identical aka monozygotic twins
What is a defining characteristic of identical twins?
They are always the same sex
What happens shortly after the zygote forms? What period is this in?
It undergoes mitosis, giving rise to two new blastomeres
30 hours after forming, the prenatal period
What is cleavage?
The division of blastomeres into smaller cells which multiply
Where do cells move during cleavage? How long does this take?
To the uterus
About 3 days
By the time a group of cells reaches the uterus (cleavage), what has occurred?
A solid ball of 16 cells called a morula has formed
What is a morula?
A solid ball of 16 cells
What happens when the morula hollows out?
It forms a blastocyst
What does a blastocyst do?
It begins to attach itself to the upper posterior wall of the uterus (endometrium)
Upper posterior wall of the uterus aka (2 things)
Back wall
Endometrium
What does the blastocyst give rise to, and what does this turn into?
Several specialized stem cells
Certain cells on the inner face of the blastocyst organize into a group called the inner cell mass
What does the formation of the inner cell mass mark? What is this called?
The beginning of the embryonic stage
An embryo
When does the embryonic stage last till?
The 8th week
When is the offspring a fetus?
After the 8th week of pregnancy and into birth
When does the placenta form? By what? What is the placenta?
During the embryonic stage
The cells surrounding the embryo and the cells of the endometrium
a complex vascular structure
What does the placenta do?
Attaches the embryo to the uterine wall and exchanges nutrients, gases, and wastes between the maternal blood and the embryo’s blood