Physio of Pregnancy: Parturition and Lactation

Question 1

What must the sperm first past through to get to this intended destination on egg?

Answer 1

Must go through follicular cells to bind to zona pellucida

Question 2

What is the acrosomal reaction triggered by? What does this reaction depend on? What fuses with what?

Answer 2

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

Question 3

What does the acrosome release? What helps move the sperm forward?

Answer 3

Hydrolytic enzymes to penetrate zona pellucida;

Their tails

Question 4

What must the sperm and oocyte do first?

Answer 4

Fuse their cell membranes

Question 5

What does the oocyte undergo upon fusion of cell membranes with sperm?

Answer 5

Cortical reaction, dependent on calcium-IP3 process preventing entry of other sperm

Question 6

What does the sperm head do after the oocyte’s second meiotic division?

Answer 6

Condense and become male pronucleus; tale degens

Question 7

How is the zygote formed? How many chromosomes do you end up with?

Answer 7

male and female pronuclei fuse; 46

Question 8

What is needed to sustain the blastocyst during the first 8 weeks of pregnancy?

Answer 8

Corpus luteum, since the placenta has not been really developed

Question 9

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?

Answer 9

Require hCG (structurally related to LH)

Question 10

Where does fertilization typically occur? When does the blastocyst get to the uterus? When does it normally implant?

Answer 10

Fallopian tubes (1 day after ovulation);
4-5 days after fertilization;
5-7 days after fertilization

Question 11

How many sperm actually make their way to the fallopian tube?

Answer 11

About 100 of about half-billion deposited in vagina

Question 12

What facilitates sperm transport?

Answer 12

Uterine, cervical, fallopian tube contractions in response to oxytocin; prostaglandins; flagella

Question 13

What does the placenta develop from?

Answer 13

Trophoblasts and adjacent cells

Question 14

What is hCG made by? How can it be useful other than sustaining the corpus luteum?

Answer 14

Syncytiotrophoblasts by the blastocysts;

Home pregnancy tests

Question 15

What are three things hCG can act as in general? In males?

Answer 15

Immunosuppressive agent, growth-promoting activity, placental development; stimulate testes to make testosterone

Question 16

How does fetus get nutrition after early weeks of pregnancy?

Answer 16

From the placenta (originally due to endometrial decidua)

Question 17

What are some key hormones supplied by the placenta? What is one group of hormones made by the placenta?

Answer 17

hCG, somatomammotropins, steroid hormones;

steroid hormones!!!

Question 18

What do the somatomammotropins do?

Answer 18

Coordinate fuel economy; promote mammary gland development in pregnant mother

Question 19

What do the four steroid hormones do?

Answer 19

Sustain the pregnancy: progesterone, estradiol, estrone, estriol

Question 20

What do rising estriol levels reflect?

Answer 20

Development and well-being of the placenta, which should help maintain high levels of estrogens and progesterone

Question 21

What unit helps make steroid hormones?

Answer 21

Maternal-fetal-placental unit

Question 22

Unlike the corpus luteum what can’t the placenta make? What does placenta lack?

Answer 22

Not enough cholesterol made;

no 17alpha-hydroxylase, 17,20-desmolase, 16-alpha hydroxylase

Question 23

In the maternal-fetal-placental unit, what does the fetus lack?

Answer 23

Lacks 3-beta-hydroxysteroid DH and aromatase

Question 24

What does the mother supply in the MFP unit? Why is this important for the mother?

Answer 24

LDL particles for cholesterol;

allows for placenta to make progesterone to sustain pregnancy once corpus luteum is gone

Question 25

What supplies the three enzymes that the placenta lacks?

Answer 25

Fetal adrenal gland and liver supply

Question 26

Why is it good that the fetus seems to be lacking certain enzymes regarding estrogen?

Answer 26

Because if fetus had the enzymes to catalyze final steps of estrogen synthesis, it would be exposed to toxic levels of estrogens

Question 27

What is the maternal response to pregnancy?

Answer 27

1. Increased blood volume (increased plasma volume, more erythrocytes since uterus is huge)
2. MAP usually remains at or lower than normal (steroid vasodilation)
3. Increased CO mostly due to increased CO (most flow to kidney, uterus)
4. Increased alveolar ventilation due to higher TV; steroids affect medullary respiratory centers
5. More dietary protein, iron, folate needed
6. Uterus larger and breasts double
7. Weight gain: 25-35 lbs
8. BMR up 15%

Question 28

What quiets the uterus during most of pregnancy?

Answer 28

Progestogens; some relaxin

Question 29

What types of contractions occur for the last month until labor begins?

Answer 29

Irregular Braxton Hicks contractions

Question 30

What initiates uterine contractions, and what sustains them?

Answer 30

Prostaglandins;

oxytocin and prostaglandins

Question 31

Where are prostaglandins made? What do they act on? What do they help do to their targets?

Answer 31

Uterus, fetal membranes, placenta;

Paracrine action to stimulate uterine smooth muscle cells; potentiate response to oxytocin and soften cervix

Question 32

During pregnancy, what increases the number of oxytocin receptors on the uterus? What leads to oxytocin being released in bursts?

Answer 32

Estrogen;

Distension of the cervix

Question 33

As labor progresses, what feedback do we see?

Answer 33

Positive feedback loops for sustained production of prostaglandins and oxytocin

Question 34

What are the stages of parturition?

Answer 34

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)

Question 35

What does oxytocin do? Prolactin? When are they both released?

Answer 35

Stimulate milk let down and uterine contractions;
Milk synthesis;
Suckling

Question 36

What four types of hormones does the breast respond to? Givve examples of each?

Answer 36

1. Mammogenic (cell proliferation - progesterone)
2. Lactogenic (initiation of milk production - prolactin)
3. Galactokinetic (promote milk ejection or let-down - oxytocin)
4. Galactopoietic (maintain milk production - prolactin primarily, cortisol)

Question 37

What surrounds the alveolus? What do these cells promote given oxytocin?

Answer 37

Contractile myoepi cells; promote milk-letdown

Question 38

What makes up the alveolus? What do they do?

Answer 38

Secretory epi cells;

secrete milk in response to prolactin

Question 39

Why would a neonate want colostrum vs. human or cow’s milk?

Answer 39

Concentrated, low-volume for immature GI tract;

less protein than

Question 40

What needs to happen to allow prolactin to do what it does?

Answer 40

Loss of the steroids (estrogens and progesterone)

Question 41

What does suckling do with respect to sensory nerves, DA, oxytocin, and GnRH?

Answer 41

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)