Repro Physl 7 Flashcards
What is the optimal time-frame for fertilization?
Between 5 days before ovulation and 1 day following ovulation
How long is sperm viable?
Up to 4-6 days
How long is the ovulated egg viable?
Between 24-48 hours
What is Capacitation?
Sperm being present in the female reproductive tract for several hours before fertilization
What occurs in capacitation?
There is a removal of proteins and carbohydrates and cholesterol from the surface of the sperm head that allows it to engage with mature ovum
How does Capacitation affect the motility of the sperm cell?
It changes from a wave-like pattern to a whip-like action of the sperm tail to propel sperm forward
What does fertilization begin with?
The fusion of a sperm and egg cell
Where does Fertilization usually occur?
In the fallopian tubes
Where do the sperm cells move between on the ovum?
Between the corona radiata granulosa cells
What is the Zona Pellucida?
A structure that surrounds a mature ovum and is a docking site for mature sperm
What serves as a receptor for proteins on the sperm cell membranes?
Glycoproteins on the zona pellucida
What triggers the Acrosome reaction?
The first sperm cell binding to the zona pellucida
What is the Acrosome Reaction?
A disruption in the sperm plasma membrane that exposes the zona pellucida to membrane enzymes
What do the acrosomal enzymes do?
Breakdown the Zona Pellucida to help the sperm cell make contact with the egg cell plasma membrane
What would occur if multiple sperm penetrate the egg?
It will no longer be viable
What prevents additional sperm from binding?
The change in membrane potential that occurs when one sperm binds to the egg
What is the cortical reaction?
When cortical granules with enzymes fuse and release their contents just below the egg plasma membrane and the zona pellucida preventing binding of additional sperm
What do the enzymes from the cortical reaction do?
- Inactivate sperm binding sites
- Harden the zona pellucida
- Prevent additional sperm from advancing
When does the second meiotic division of an ovum occur?
After it completes fertilization
What does each pronuclei from the egg and sperm contain?
23 chromosomes
How long is the conceptus housed in the fallopian tube?
3-4 days
What is the holding of the conceptus in the fallopian tube facilitated by?
Estrogen that causes the contraction at the smooth muscle at junction of fallopian tube with uterus
What permits conceptus movement into the uterus????
Permits conceptus movement into the uterus
What happens once the conceptus reaches the uterus?
It floats freely in the intrauterine fluid for about 3 days and divides and while the fluid provides nutrients
What occurs in the Blastocyst stage?
When the cells are no longer totipotent (are specific to tissues) and cell differentiation occurs
What is the Trophoblast?
The outer layer of cells in the blastocyst
What does the inner mass in the blastocyst do?
Give rise to the baby
When does implantation begin?
7 days post-ovulation or day 21 of the menstrual cycle
What happens during implantation?
The blastocyst embeds into the endometrium
Which side of the blastocyst is attracted to the endometrium?
The side with the inner cell mass
What does the blastocyst do once in the endometrium?
It releases enzymes that breakdown and digest cells of the endometrium that release nutrients and cell signaling mediators to support the embryo
What kind of tissues is the placenta formed by?
Fetal and maternal tissues
Why is implantation important?
Because the trophoblast cells can only maintain needs of the embryo for so long
What allows for exchange between the mother and fetus for the pregnancy?
The placenta
What is the embryonic portion of the the placenta comprised of?
The chorion from the outer trophoblast cells
What is the maternal portion of the placenta comprised of?
The endometrium
What are Chorionic villi?
Projections from the chorion into the endometrium that has a rich capillary network
Since maternal and fetal blood never mix, how does the exchange of nutrients occur?
Through diffusion in the sinuses
What is the Amniotic cavity formed between?
An inner cell mass and chorion
What is the amniotic cavity epithelial lining (amniotic sac) derived from?
The inner cell mass
What does the Amniotic sac fuse with?
The inner surface of the chorion
What is amniotic fluid important for?
Buffer the baby against mechanical forces and temperature fluctuations
What are estrogen and progesterone levels like during pregnancy?
There is a continuous rise in estrogen and progesterone
How are estrogen and progesterone levels affected by delivery?
They plummet
What does estrogen do during pregnancy?
- Stimulates growth of uterine muscle mass
* Supplies contractile force required for delivery
What does progesterone do during pregnancy?
Inhibits uterine contractility to prevent premature delivery
Where does all the estrogen and progesterone come from during pregnancy?
The corpus luteum
What supports the function of the corpus luteum if fertilization occurs?
hCG
What is hCG produced by?
Trophoblast cells in the blastocyst of the embryo
What is used to detect pregnancy?
hCG from the trophoblast cells of the blastocyst
When does estrogen and progesterone production from the corpus luteum stop?
During the second trimester when it is taken over by the placenta
What are androgens as precursors for estrogen provided to the placenta by?
- Maternal ovaries
- Adrenal glands
- Fetal adrenal glands
What does Aromatase in the placenta do?
Converts androgen to estrogen
