Pregnancy, Parturition, and Lactation Flashcards
1
Q
fertilization
A
- sperm binds to the zona pellucida, which is comprised of 3 glycoproteins that form a mucous-like lattice work
- the acrosomal reaction is triggered by sperm binding to one of the glycoproteins. calcium dependent process leads to fusion of the acrosome with the sperm cell plasma membrane
- hydrolytic enzymes released from the acrosome penetrate the zona pellucida. sperm also oscillates to aid in penetration process
- cell membranes of sperm and oocyte fuse. cytoplasmic portion of sperm head and tail enter oocyte
- oocyte undergoes the cortical reaction, preventing entry of other sperm (polyspermy)- calcium dependent process
- the oocyte completes its 2nd meiotic division and a 2nd polar body is expelles
- sperm head condenses and becomes male pronucleus
- male and female pronuclei fuse, forming the zygote
2
Q
menstrual cycle
A
- FSH causes follicles to mature
- LH surge causes ovulation
- luteal phase has progesterone
- estrogen causes positive feedback at the end of the follicular phase
3
Q
fertilization and implantation
A
- fertilization occurs in the fallopian tube
- 3-5 days pass as the blastocyst (100 cells) goes to the uterus, and another 1-2 days before implantation
- of the almost half billion of sperm deposited in the vagina, less than a hundred make their way to the ampulla of the fallopian tube
- in addition to flagella motility, sperm transport is facilitated by contractions of the uterus, cervix, and fallopian tubes in response to oxytocin released during the female orgasm, and prostaglandins in the male seminal fluid
- at this early stage of pregnancy, the corpus luteum continues to produce steroid hormones to maintain pregnancy as the placenta develops from trophoplasts and adjacent cells
4
Q
hCG
A
- rescues corpus luteum after implantation
- produced by syncytiotrophoblasts by the blastocysts
- closely related to LH and sustains the corpus luteum in the face of declining levels of maternal LH, so sex steroid production increases
- HCG also acts as an immunosuppresive agen, has growth promoting ability, and promotes placental development
- can be measured in the urine shortly after the blastocyst implants and is the basis for most home pregnancy tests
- also stimulates the testes of the male fetus to produce testosterone, leading to male sex organ development
5
Q
early fetal nutrition
A
- derived from the endometrial decidua until the placental develops
- subsequent nutrition through placenta
- about 12 weeks placenta is fully grown and developed
6
Q
key hormones supplied by the placenta
A
- steroids
- hCG
- somatomammotropins
- critical for steroid hormone synthesis
- produces amines, polypeptides, proteins, glycoproteins
- hCG is most important peptide hormone
- progesterone
- estrone
- estradiol
- estriol
7
Q
somatomammotropins
A
- coordinate fuel economy by contributing to the conversion of glucose to fatty acids and ketones
- promote mammary gland development in the pregnant mother
8
Q
steroid hormones
A
- rise rapidly and remain elevated during pregnancy
- progesterone spikes near 8 and 4 weeks before, then jump up and are sustained when pregnant
- after 8 weeks of gestation, coordinated activity of the maternal placental fetal unit maintains high levels of estrogens and progesterone
9
Q
mother and fetus cooperation
A
- produce pregnancy hormones
- placenta needs the assistance of mother and fetus to produce steroid hormones
- unlike corpus luteum, the placenta itself cannot manufacture adequare amounts of cholesterol
- placenta lacks 2 key enzymes needed for synthesis of estrone and estradiol
- lacks a third enzyme needed for synthesis of estriol
10
Q
placenta
A
- has 3B hydroxysteroid dehydrogenase
- aromatase
11
Q
fetus
A
- has 17a hydroxylase
- has 17,20 desmolase (same thing)
- has 16 a hydroxylase
12
Q
common to placenta and fetus
A
-17 B hydroxysteroid dehydrogenase
13
Q
maternal fetal placental unit
A
- mother supplies most of the cholesterol as LDL particles, which allows placenta to generate large amts of progesterone for export to the mother to maintain pregnancy
- fetal adrenal gland and liver supply the three enzymes that the placenta lacks
- fetus lacks the enzymes that catalyze the final steps in estrogen synthesis
- if fetus alone was able to generate estrogens it would be exposed to dangerously high levels of hormones needed by the mother
14
Q
maternal response to pregnancy
A
- increased blood volume due to increased plasma volume and erythrocytes meets the demands of the enlarged uterus and its hypertrophied vascular system
- MAP usually decreases during midpregnancy (vasodilation effects of steroid hormones), then rises during the 3rd trimester, but usually remains at or lower than normal
- increased CO primarily during the 1st trimester due to and increase in stroke volume. much of the increased blood flow is to the kidney and uterus, which some increase to heart, skin, and breast
- increased alveolar ventilation due to increased tidal volume are early physiologic changes due to steroid effects on medullary resp centers, increased alveolar ventilation results in decreased maternal arterial pCO2
- increased demand for dietary protein (as well as iron and folic acid, reflecting increased production of blood cells
- uterus increases from 50 g to 1100 g, breasts double in size
- average weight gain is 25-35 lbs (fetus is 8)
- BMR increases 15%, especially in the latter half of the pregnancy
15
Q
parturition
A
- may be triggered by an increase in fetal production of cortisol near term, which increases the ratio of estrogen/progesterone, and thus the sensitivity of the uterus to contractile stimuli
- combo of endocrine, mechanical stretching, paracrine factos involved
- uterus is quiescent throughout most of pregnancy due to the presence of progestogens and relaxin
- during last month, irregular braxton hicks contractions begin until actual labor
- prostaglandins initiate contractions, and the are sustained by oxytocin and more prostaglandins
- during pregnancy, estrogen increases the number of oxytocin receptors on myometrial tissue in the uterus
- maternal oxytocin is released in bursts with increasing during labor, occurs in response to distension of the cervix
- positive feedback loops sustain production of prostaglandins and oxytocin as labor progresses
- relaxin is produced by corpus luteum, placenta, decidua, increased during labor to soften cervix
- involution of the uterus occurs after delivery in response to the changed endocrine milieu
