Physio of Pregnancy: Parturition and Lactation Flashcards
What must the sperm first past through to get to this intended destination on egg?
Must go through follicular cells to bind to zona pellucida
What is the acrosomal reaction triggered by? What does this reaction depend on? What fuses with what?
Binding of sperm to one of the glycoproteins of zona pellucida;
Depends on IC Ca in sperm;
Acrosome at head of sperm fuses with sperm cell plasma membrane –> exocytosis
What does the acrosome release? What helps move the sperm forward?
Hydrolytic enzymes to penetrate zona pellucida;
Their tails
What must the sperm and oocyte do first?
Fuse their cell membranes
What does the oocyte undergo upon fusion of cell membranes with sperm?
Cortical reaction, dependent on calcium-IP3 process preventing entry of other sperm
What does the sperm head do after the oocyte’s second meiotic division?
Condense and become male pronucleus; tale degens
How is the zygote formed? How many chromosomes do you end up with?
male and female pronuclei fuse; 46
What is needed to sustain the blastocyst during the first 8 weeks of pregnancy?
Corpus luteum, since the placenta has not been really developed
When you don’t have LH to luteinize thecal and granulosal cells, what helps make steroid hormones to sustain the pregnancy? How is this related to LH?
Require hCG (structurally related to LH)
Where does fertilization typically occur? When does the blastocyst get to the uterus? When does it normally implant?
Fallopian tubes (1 day after ovulation);
4-5 days after fertilization;
5-7 days after fertilization
How many sperm actually make their way to the fallopian tube?
About 100 of about half-billion deposited in vagina
What facilitates sperm transport?
Uterine, cervical, fallopian tube contractions in response to oxytocin; prostaglandins; flagella
What does the placenta develop from?
Trophoblasts and adjacent cells
What is hCG made by? How can it be useful other than sustaining the corpus luteum?
Syncytiotrophoblasts by the blastocysts;
Home pregnancy tests
What are three things hCG can act as in general? In males?
Immunosuppressive agent, growth-promoting activity, placental development; stimulate testes to make testosterone
How does fetus get nutrition after early weeks of pregnancy?
From the placenta (originally due to endometrial decidua)
What are some key hormones supplied by the placenta? What is one group of hormones made by the placenta?
hCG, somatomammotropins, steroid hormones;
steroid hormones!!!
What do the somatomammotropins do?
Coordinate fuel economy; promote mammary gland development in pregnant mother
What do the four steroid hormones do?
Sustain the pregnancy: progesterone, estradiol, estrone, estriol
What do rising estriol levels reflect?
Development and well-being of the placenta, which should help maintain high levels of estrogens and progesterone
What unit helps make steroid hormones?
Maternal-fetal-placental unit
Unlike the corpus luteum what can’t the placenta make? What does placenta lack?
Not enough cholesterol made;
no 17alpha-hydroxylase, 17,20-desmolase, 16-alpha hydroxylase
In the maternal-fetal-placental unit, what does the fetus lack?
Lacks 3-beta-hydroxysteroid DH and aromatase
What does the mother supply in the MFP unit? Why is this important for the mother?
LDL particles for cholesterol;
allows for placenta to make progesterone to sustain pregnancy once corpus luteum is gone
What supplies the three enzymes that the placenta lacks?
Fetal adrenal gland and liver supply
Why is it good that the fetus seems to be lacking certain enzymes regarding estrogen?
Because if fetus had the enzymes to catalyze final steps of estrogen synthesis, it would be exposed to toxic levels of estrogens
What is the maternal response to pregnancy?
- Increased blood volume (increased plasma volume, more erythrocytes since uterus is huge)
- MAP usually remains at or lower than normal (steroid vasodilation)
- Increased CO mostly due to increased CO (most flow to kidney, uterus)
- Increased alveolar ventilation due to higher TV; steroids affect medullary respiratory centers
- More dietary protein, iron, folate needed
- Uterus larger and breasts double
- Weight gain: 25-35 lbs
- BMR up 15%
What quiets the uterus during most of pregnancy?
Progestogens; some relaxin
What types of contractions occur for the last month until labor begins?
Irregular Braxton Hicks contractions
What initiates uterine contractions, and what sustains them?
Prostaglandins;
oxytocin and prostaglandins
Where are prostaglandins made? What do they act on? What do they help do to their targets?
Uterus, fetal membranes, placenta;
Paracrine action to stimulate uterine smooth muscle cells; potentiate response to oxytocin and soften cervix
During pregnancy, what increases the number of oxytocin receptors on the uterus? What leads to oxytocin being released in bursts?
Estrogen;
Distension of the cervix
As labor progresses, what feedback do we see?
Positive feedback loops for sustained production of prostaglandins and oxytocin
What are the stages of parturition?
0: uterine tranquility
1: uterine awakening and nearing complete cervical dilatation (more OT receptors and gap junctions)
2: active labor (complete cervical dilatation to newborn delivery)
3: delivery of fetus and final uterine contraction (lactation aides with this latter step)
What does oxytocin do? Prolactin? When are they both released?
Stimulate milk let down and uterine contractions;
Milk synthesis;
Suckling
What four types of hormones does the breast respond to? Givve examples of each?
- Mammogenic (cell proliferation - progesterone)
- Lactogenic (initiation of milk production - prolactin)
- Galactokinetic (promote milk ejection or let-down - oxytocin)
- Galactopoietic (maintain milk production - prolactin primarily, cortisol)
What surrounds the alveolus? What do these cells promote given oxytocin?
Contractile myoepi cells; promote milk-letdown
What makes up the alveolus? What do they do?
Secretory epi cells;
secrete milk in response to prolactin
Why would a neonate want colostrum vs. human or cow’s milk?
Concentrated, low-volume for immature GI tract;
less protein than
What needs to happen to allow prolactin to do what it does?
Loss of the steroids (estrogens and progesterone)
What does suckling do with respect to sensory nerves, DA, oxytocin, and GnRH?
Stimulates sensory nerves;
inhibits neurons that release DA;
Production and release of oxytocin from PP (mostly PVN, some supraoptic);
inhibit GnRH release (inhibits the ovarian cycle)
