Pregnancy - Checked and Complete Flashcards
Define the acrosomal reaction
Acrosome contents of sperm are released and allow entrance of sperm through the egg’s zona pellucida
Without this, sperm could fuse but not penetrate egg
Define cortical reaction
**Egg preventing more sperm from fertilizing it by releasing vesicles that harden and create obstacles for additonal sperm to penetrate the egg. **
What are the 2 times in a female that Meiosis stops/resumes?
1) Stops at Prophase I until puberty
2) Stops at Metaphase II until fertilization
When does implantation begin?
About 1 week after fertilization
How is the corpus luteum signalled to be maintained after fertilization?
** Human chorionic gonadotrophin (hCG) secreted by the syncytiotrophoblast of the implanting blastocyst**
How does hCG have its effect?
Binds to LH receptors in ovary
What is the role of hCG?
hCG promotes corpus luteum to secrete progesterone
hCG also helps repel a mother’s immune cells while the fetus and placenta develops
hCG related to morning sickness
How early can hCG be detected for pregnancy test?
By 9 days
What is the role of progesterone during pregnancy?
Is secreted the entire time - increasing amounts until birth
Produced by corpus luteum until placenta can take over
Effects: Maintain endometrium, maintain firm cervix, increase maternal appetite and fat deposition, increases alveolar ventilation
What is the role of estrogen during pregnancy?
Increase uterine muscle strength
Increase oxytocin receptors
What is the role of fetal cortisol?
Promotes maturation of fetal lungs
Stimulates closure of ductus arteriosus
Describe uterine contraction during birth
**Uterine muscle contractions are dependent on extracellular Ca+2 **
Prostaglandins increase the concentration of intracellular Ca+2
Oxytocin increases the rate of Ca influx and lowers the excitation threshold of the muscle
Uterine muscle cells hypertrophy to 10 times the original size
Describe the hormones necessary for cervix compliance and expansion.
Prostaglandins E and F
Describe how birth is triggered
CRH increases, to increase ACTH
This increases fetal secretion of androgens from the adrenal gland
The placenta converts the androgens into estrogen
Estrogen increases gap junctions in myometrium (coordinated contractions of uterus), increases prostaglandins (cervix dilation), increases oxytocin receptors (stronger, more frequent contractions)
Cortisol also secreted from fetal adrenal cortex to prepare the lungs
What is required for maternal milk secretion?
Estrogen and Progesterone must dissapear from circulation
Prolactin must remain elevated
Need suckling to trigger milk secretion
