BSI 2 Lecture 59-60: Pregnancy and Lactation Flashcards
What happens to the ovum just prior to ovulation?
It undergoes meiosis with the release of the first polar body
When the ovum is released and makes it into the fallopian tube, what is responsible for its movement?
Estrogen-activated cilia
What stimulates the contractions that aids the travel of sperm?
Prostaglandins and oxytocin
What must the sperm do to begin the process of fertilization?
Penetrate several layers of granulosa cells and then bind to the zona pellucida
What happens when a sperm cell makes it through the zona pellucida and binds to the membrane of the egg?
The egg releases contents of secretory vesicles, and these contents enter the zona pellucida preventing multiple sperm from entering the cell
What happens as soon as the sperm is inside the egg cell?
The ovum undergoes the second round of meiosis and ejects the second polar body which allows the sperm and egg to unite
Why is the ovum trapped in the fallopian tube for about 3 days after fertilization?
So it has time to become the blastoid
What is responsible for relaxing the contractions at the isthmus once the ovum has become a blastoid?
An increase in progesterone from the corpus luteum
Once in the uterus, how long does it take for the ovum to implant?
About 1-3 days (5-6 days after ovulation) in order to create an environment necessary for survival
What causes actual implantation?
Trophoblast cells of the blastocyst secreting proteolytic enzymes that allow it access and form a secure connection to the endometrium
As soon as the blastocyst attaches, what cells rapidly divide, and what do they form?
The trophoblast and other cells divide to form the placenta and uterine membranes
What provides nourishment until the placenta takes over?
Progesterone release from the corpus luteum causes endometrial proliferation and release of nourishment
When does the placenta start to provide nourishment?
At about 8 weeks until birth
When does the embryonic heart start to beat?
After about 16 days
Fetal hemoglobin has a higher affinity for oxygen, but how does the amount of hemoglobin in the blood compare to that of the mother?
Fetal blood contains about 50% more Hb per unit voume
How does the Bohr effect enhance oxygen delivery to the fetus?
There is an increase in CO2 diffusing from fetal blood which lowers the pH of the mother’s blood. The causes the Bohr effect and a rightward shift in the Hb-O2 curve. This causes a decreased affinity between hemoglobin and oxygen allowing the fetus to receive more oxygen
What produces human chorionic gonadotropin?
Trophoblast cells surrounding the fertilized egg
What does human chorionic gonadotropin act like?
A gonadotropin (specifically LH)
What is the purpose of chorionic gonadotropin?
To maintain the corpus luteum until the placenta can take over
What does the corpus luteum secrete?
Progesterone and estrogens to prevent menstruation and to stimulate endometrium growth
What is pregnancy test looking for?
Presence of hCG in the urine