pregnancy, parturition, and lactation vallano Flashcards
fertilization involves morphological and biochemical events
- ovum is protected and nurtured by follicular cells. sperm weaves past follicular cells and binds to zona pellucida which is comprised of 3 glycoproteins that form a mucus like latticework.
- a rise in Ca inside sperm cell causes the release of the acrososme- acrosomal rxn that contains hydrolytic enzymes
- hydrolytic enzymes released from acrosome penetrate zona pellucida sperm also oscillate to aid in this.
- cell membrane of sperm and oocyte fuse. contents of sperm enter oocyte and its membrane stays behind.
- oocyte now undergoes the cortical rxn where it prevnts other sperm from binding. his is a Ca/IP3 dependant thing. you get the hardeining from the exocytosis of granules that were under the plasma membrane. enzymes released cause the zona pellucida to harden.
- the oocyte undergoes its second meiotic division and the 2rd polar body is expelled.
- sperm head condenses and becomes the male pronucleus
- male and female pronuclei fuse forming the zygote.
menstrual cycle
-ovulation occurs on day 14, and fertilzation occurs 24 hrs later
- during follicular phase, many primary follicles undergo developmnt in response to FSH and synthesisze androgens which are converted to estradiol using LH. one follicle matures and the others regress. uterine endometrium proliferates in response to estradiol.
-the follicular phase, especially the late follicular phase is proliferative for the uterus. high levels of berta estradiol during the late follicular phase help make it proliferative. do ovum is released after the proliferation of the uterus.
-midcycle, estradiol rises to a level that causes positive feedback and a surge in LH and FSH occurs in pituitary and leads to ovulation.
-luteal phase is after and you have a mature follicle that becomes the corpus luteum and secretes estrogen and progesterone. uterus undergoes more secretory changes.and if pregrancy doesnt occur, endometrial sloughing occurs, marking beginning of new cycle.
-after ovulation you have the secretory phase where glandular, vascular, mucus, glycogen occurs. you dont want to implant the blastocyst till the uterus is ready with all that so you take 7 days for blastocyst to travel the tubes and implants after 7 days. aka 8 days since ovum release.
-at the beginning of fertilization, you dont have a placenta yet so you need the corpus luterum for the first 8 weeks to sustain the blastocyst. LH will luteinize the cells and produce steroids needed to sustain the blastocyst. LH hormone levels drop though so HCG binds to LH receptors and keeps the actions active. LH and HCG are very closely related structurally.
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time course for fertilization and implantation
-fertilization occurs on day 1 in fallopian tube. 3-5 days later, you have a blastocyst that gets to uterus, that is 100 cells. implantation occurs 1-2 days later.
-half a billion sperm enter, less than 100 make it to ampulla of tube
-flagella motility helps transport, so does orgasm of woman from oxytocin release and prostaglandins in sperm from men
-at this early stage, corpus luteum keeps producing steroid hormones to maintain pregnancy as the placenta develops from trophoblasts and adjacent cells.
-if you only had one ovary and one fallopian tube on the other side, somehow the egg would get to the other fallopian tube
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after implantation, in the first trimester, hCG is really important
- hCG is produced in syntitrophoblasts by blastocyst
- closely related to LH and it sustains the corpus luteum as maternal LH levels fall. helps sex steroid production increase
- hCG is immunosupressive, promotes growth, and promotes placental development. it can be measures in the urine shortly after blastocyst implants, and is home pregnancy test hormone. hCG also stimulates tester in male fetus to produce testosterone to make male sex organs.
- hCG causes morning sickness in first trimester.
- hCG is good for the first trimester but its limitedin its steroid prodcuing abilites so you need the pacenta to grow
- the rise in hCG is needed for the sustenenace and production of steroids b the corpus luteum as LH declies
- early fetus gets nutrition from the endometrium of the uterus as the placenta develops
-fetus gets sustenance for 8 weeks from the endometrial lining that was made by progesterone. eventually fetus gets nutrition from diffusion through the placenta.
hormones made by placenta
-key hormones from placenta: steroid hormones, hCG,( most important placetal peptide hormone) and somatomammotropins (promote mammary gland development in mother. coordinate fuel economy by conversion of glucose to fatty acids and ketones)
-placenta criitcal for steroid hormone ynthesis: progesterone, estrone, estradiol, estratriol
-also makes amines, polypeptides, proteins, and glycoproteins.
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- steroid hormones rise rapidly and stay elevated during pregnancy
- prior to preganncy, progesterone spikes in ovulatory cycles preceding fertilization time 0
- estratriol starts being made at 8 weeks, and denotes adequate development of the PLACENTA at 8 weeks
- there is a logarthmic increase
mother, fetus, and palacenta make the maternal fetal placental unit and all help to make pregnancy hormones
- placenta needs help from mom and fetus to make steroid hormones
- unline corpus luteum, placenta cant make enough cholesterol precursor for steroid hormone synthesis
- placenta lacks 2 enzymes for estrone and estradiol synthesis and lacks a third enzyme needed for estriol synthesis
- mom gives cholesterol
- placenta can make pregnenolone and progesterone. to make estrogen though, it takes the pregnenolone, and uses the fetus adrenal and liver to make DHEA and then goes back into placenta to make estrogens. which then go back to mom.
maternal response to pregnancy
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- increased blood volume from increased plama volume and increased erythrocytes meets the demand of the enlarged uterus and vascular system
- MAP decreased midpregancy bc of vasodialtion bc of steroid hormones, but then rises in 3rd trimester. it ususally stays at or lower than normal
- increased CO in first trimester by 35-40% bc of increase in stroke volume. alot of the increased blood flow is to kidneys, uterus, heart, skin and breats
- increased alveolar ventilation- bc of increased tidal volume, and steroid effects on medullary respiratory centers. increased tidal volume results in decreased maternal PCO2.
- increased demand for protein, iron, and folic acid bc of increased production of blood cells
- uterus increased from 50g to 1100 g and breasts double in size
- average weight gain is 25-35 pounds and fetus is 8lbs.
- BMR increases 15%
parturition is birth of baby. triggered by several stes. may be triggered by an increase in fetal production of cortisol near term which increases the ratio of estrogen to progesterone and thus the sensitivity of the uterus to contractile stimuls
-in animal studies, possible trigger is strogen to progesterone ratio. estrogen causes contraction and progsesterone causes quiescence.
- oxytocin is not the trigger for labor
- baby’s head stretches the cervix. cervical stretch then excites fundic contraction through mechanical stretch receptors. fundic contraction pushes the baby down and stretches cervix some more. cycle repeats over and over. oxytocon is released in response to this stretch
- stage 0 is uterine tranquility
- stage 1 is uterine aakening, initiation of parturition, extending to complete cervical dilation. physiological changes are increase in the number of gap junctions bw myometrial cells, increase in number of oxytocin receptors. this helps contractions be stronger and more forceful.
- stage 2 is active labor and coplete cerival dilation to delviery of newborn
- stage 3 is delivery of fetus to expulsion of the placenta and the final uterine cotraction. this prevents hemmorhage,
- endocrine, paracrine, and mechanical stretch all involved in parturiotion.
- uterus is quiet until the last month when braxon hicks irregularcontractions start, and then regular contractions for labor
- prostaglandins initiate contraction, and they are sustained by oxytocin and more prostag;andns. you give RU486 and prostaglandins at abortion to be sure you got the fetus.
- the uterus, fetal membrane, and placenta make prostagladins which act by paracrne machanism to stimulate uterine smooth muscle, promote formation of gap junctions, which then poteintiated affect of oxytocin and causing a softening or effacement of cervix
- in pregancy, estrogen increased number of oxytocin receptors on myometrial tissue 80 fold. maternal oxytocin is relased in bursts w/ increasing freq in labor. occurs in response to cervix distention, furgenson reflex
- positive feedback sustain prostaglandin and oxytocin as labor progresses
- relaxin produced by corpus luteum, placenta, and uterus. it softens the cervix
- involution of uterus occurs after delivery bc of chsnged endocrine stuff.
oxytocin and prolactin
oxytocin is for milk let down and uterine contraction
prolactin is for milk synthesis
both are released in sucking
lactation- the breats respond to multiple hormones during and after pregnancy.
- mammogenic: promote cell proliferentiation. estrogen and progesterone.
- lactogenic: initation of milk production. prolactin
- galactogenic: milk ejection. oxytocin and vasopressin.
- galactopoitic: maintain milk production. prolactin and cortisol.
alveolus is functional secretory unit of breasts
- organized into lobules and drain into a ductule. groups of ductules drain into duct.
- contractile myoepithelial cells surround each alveolus and adipose cells and promote milk let down in oxytocin response
- secretory epithelial cells secrete milk in prolactin response and cortisol
colostrum is secreted upon initiation of lactation
- colostrum is first milk. concentrated low volume nutrition for the baby’s GI tract for first few days. has little or no fat compared to mature human milk. has antibodies, just like mature human milk.
- cow milk has higher electrolyte conc and more protein than human milk bc of casein. baby GI cant tolerate cow milk
prolactin maintians milk production after parturition
-estrogen and progesterone are critical for breast development before birth in pregnancy but they prevent secretion of milk. after birth they drop and then prolactin is free to have milk be released.
