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Phys Spring 5: Lec 3
Pregnancy & Lactation
| Question | Answer |
|---|---|
| Where to almost all fertilizations occur? | The upper oviduct |
| How does the developing egg get nutrients in the oviduct? | Epithelial cells that line the oviduct secrete nutrients for the developing egg |
| TRUE OR FALSE: Eggs can be lost into the abdomen after ovulation | TRUE |
| How does the egg get into the oviduct? | After ovulation the egg is brushed by the fimbria into the infundibulum of the oviduct. |
| About how long does it take for the egg to get thru the oviduct to the uterus? | 3-5 days |
| How does the egg move thru the oviduct toward the uterus? | Cilia lining the oviduct generate flow that carries the egg to the uterus |
| What stage does a fertilized egg reach before reaching the uterus? | The blastocyst stage (~100 cells) |
| When does implantation occur? | 5-7 days after fertilization |
| What effect does progesterone have on the endometrium? | Stimulates accumulation of glycogen within the endometrium |
| What does the outer layer of cells of the blastocyst become? | The trophoblasts |
| Where does implantation usually occur? | In the upper uterus near the entrance of the oviducts |
| What is an ectopic pregnancy? | Implantation into the wall of the ovidcut |
| Why are ectopic pregnancies dangerous? | Rupture of the thin wall of the oviduct is likely, leading to internal bleeding and possible hemorrhagic shock & peritonitis |
| What happens with the trophoblasts after the blastocyst has made contact w/the lining of the endometrium? | The trophoblasts have penetrated the endometrial lining, and have begun digesting endometrial cells |
| What are the actions of the trophoblasts? | Extends between endometrial cells, secrete proteolytic enzymes, bind to proteins on the surface of endometrial cells, and absorb nutrients from these cells |
| How does the blastocyst get nutrients during the fist few weeks after implantation? | The trophoblasts digest the swollen endometrial cells |
| What happens to the trophoblasts about one week after implantation? | Some of the trophoblast cell membranes disintegrate and form the syncytium. |
| How does the chorion develop? | The chorion forms under the trophoblast layer and extends villi into the surrounding endometrium |
| TRUE OR FALSE: The yolk sac expands to surround the developing fetus | FALSE - the AMNIOTIC CAVITY expands to surround the developing fetus |
| How is the chorion involved in establishing blood flow to the fetus? | Extensions from the chorion cells penetrate into the lower layers of the endometrium, and fetal capillaries grow into these extensions |
| What is another name for the fetal capillaries that grow into the extensions of the chorion? | Placental villi |
| TRUE OR FALSE: the maternal arteries are directly connected to the placental villi | FALSE - blood filled sinuses from maternal arteries grow around the villi |
| What is the placenta? | A mass of tissue formed from placental villi and maternal blood vessels |
| Describe the structure of a placental villus | Each villus is an extension of the chorion into the endometrium. They contain capillaries from the umbilical vessels and each is surrounded by a blood-filled sinus from maternal vessels |
| TRUE OR FALSE: maternal arteries and veins drain into one continuous sinus around the chorionic villi | TRUE |
| TRUE OR FALSE: Umbilical arteries are the only blood vessels found in the umbilical cord | FALSE - both umbilical arteries AND veins |
| TRUE OR FALSE: Maternal arteries carry blood away from the fetus to the mother and maternal veins carry blood to the fetus from the mother | FALSE - maternal VEINS carry blood away from the fetus to the mother and maternal ARTERIES carry blood to the fetus from the mother |
| Are the chorionic villi located closer to the top of the uterus or closer to the cervix? | Closer to the top of the uterus |
| What are the (4) fxns of the placenta? | 1. Transport nutrients into the fetus; 2. Diffuse waste out of the fetus; 3. Exchange O2 and CO2; 4. Production of hormones |
| What are the hormones produced by the placenta? | Progesterone, estrogen, HCG, HCS |
| Why can oxygen diffuse to the fetus? | At the placenta, maternal Po2 is ~50mmHg and fetal Po2 is only ~30mmHg, creating a gradient for diffusion |
| TRUE OR FALSE: Fetal Hb can carry more O2 at high Po2 than maternal Hb | Fetal Hb can carry more O2 at LOW Po2 than maternal Hb |
| What is the double Bohr effect? | As maternal blood becomes more acidic in the placenta d/t CO2 from the fetus, the maternal Po2 curve shifts R. As fetal blood becomes more alkaline d/t loss of CO2 to mom, the fetal curve shifts L. Both shifts favor O2 transfer to the fetus. |
| When does HCG production by the fetus spike ? | Between weeks 4-8, then will slowly drop and at ~24 weeks plateaus at levels lower than estrogen & progesterone levels. |
| Are progesterone and estrogen levels high at the same time HCG is high? | No, progesterone and estrogen levels start off low and are increasingly secreted by the placenta throughout pregnancy. |
| Where is HCG produced? | By the trophoblasts |
| What does HCG do in regards to the corpus luteum? | Similar to LH, it stimulates growth of the corpus luteum in order to maintain progesterone & estrogen secretion for several months |
| What does HCG do in regards to the endometrial cells? | Inc apoptosis |
| What does HCG do in regards to the maternal T cells? | Inc apoptosis in order to suppress maternal immune response to the fetus |
| What additional fxn does HCG have if the fetus is male? | Stimulates testosterone secretion by the testes |
| How do commercial pregnancy tests work? | HCG leaks across the placenta and is excreted in mom's urine. Pregnancy tests have antibodies to HCG |
| Where is HCS produced? | By the trophoblasts |
| What does HCS do to maternal glucose levels? | Similar to GH, it decreases maternal glucose uptake, increasing glucose availability for the fetus |
| What may be an adverse effect of HCS? | It may be a cause of gestational diabetes |
| What does HCS do to maternal FFA levels? | Inc maternal FFA release |
| What does HCS do to maternal breast tissue? | Along with prolactin, it promotes growth of maternal breast tissue |
| What is another name for HCS | HPL - human placental lactogen |
| Where is placental estrogen produced? | By the trophoblasts |
| What are the (3) fxns of placental estrogen? | 1. Enhances growth of the endometrium and uterine smooth muscle; 2. Enhances growth of breast tissue; 3. Relaxes pelvic ligaments |
| What are the (5) fxns of placental progesterone? | 1. Maintains viability of the endometrium; 2. Relaxes smooth muscle, dec uterine contractions; 3. Inc body temp; 4. Inhibits lactation during pregnancy; 5. has anti-inflammatory effect, inhibiting maternal immune response to the fetus |
| How does placental progesterone maintain viability of the endometrium? | Inc synthesis of albumin & glycogen, and inc growth of spiral arteries |
| How does the uterus change with pregnancy? | It grows from ~50g to ~1100g |
| How do the breasts change with pregnancy? | They enlarge |
| How does body weight change with pregnancy? | It inc by ~24+ lbs: 7lb fetus + 4lb amniotic fluid & placenta + 2lb uterus growth + 2lbs breast enlargement + 6lbs blood & extracellular fluid + 3lbs fat storage |
| How does the basal metabolic rate change with pregnancy? | It inc ~15% in response to inc thyroxine and cortisone |
| How do Fe & Ca levvels change with pregnancy? | Fe & Ca reserves are depleted |
| How does the pituitary respond to pregnancy? | Inc production of ACTH, TSH, and PRL, dec FSH & LH secretion |
| What is an effect of inc ACTH? | More ACTH --> more MSH --> hair & freckles darken |
| How does the adrenal cortex respond to pregnancy? | Inc cortisone, conversion of muscle to AA; inc aldosterone for salt & water retention |
| How does the thyroid respond to pregnancy? | inc metabolic rate & body temp |
| How does the parathyroid respond to pregnancy? | Inc PTH and Ca mobilization from mother's bones |
| Where is relaxin produced? | from the corpus luteum & placenta |
| What is the fxn of relxin? | enhances collagen breakdown; helps relax the pubic symphysis |
| How does cardiac output change with pregnancy? | Inc 30-40%; 625mL/min thru placenta at term; inc basal metabolic rate |
| How does blood volume change with pregnancy? | Inc 1-2L; inc aldosterone retains fluid, inc EPO inc # of RBCs |
| How does urine output change with pregnancy? | only slightly inc; Na+ & water reabsorption inc ~50%, GFR inc ~50%, and amniotic fluid (500mL-1L) is replaced |
| How often is amniotic fluid replaced? | amniotic fluid (500mL-1L) is replaced every 3 hours; flow is mostly from detal urine to amnionic blood vessels |
| When does birth occur? | ~38 weeks after conception, or ~40 weeks after the beginning of the last cycle |
| What causes the gradual inc in uterine contractions preceding birth? | Progesterone secretion, which had been inhibiting contractions, decreases near term |
| What happens to progesterone & estrogen levels near term? | Progesterone levels dec, estrogen levels remain high |
| TRUE OR FALSE: muscles of the uterus express many more oxytocin receptors in response to estrogen as time of birth approaches | TRUE |
| How do fetal adrenal gland secretions change near the time of birth? | Secrete more cortisol |
| How do fetal tissue secretions change near the time of birth? | Secrete more prostaglandins (PGE2 & PGF2) at the time of birth |
| Relate oxytocin and uterine contractions at birth | Once contractions reach a threshold, oxytocin release by the pituitary inc, causing stronger contractions and positive feedback. |
| Besides inc strength contractions, what other events happen at birth? | The cervix dilates from almost closed to ~8-10cm; the amniotic sac breaks; and the contractions at the upper end of the uterus pushes the infant against the cervix and out through the birth canal |
| TRUE OR FALSE: uterine contractions are stronger near the cervix | FALSE - uterine contractions are stronger at the upper end of the uterus |
| What happens to the uterus after birth? | Continues contracting and shrinks in size |
| How is the placenta delivered after birth? | Continued contracting and shrinkage of the uterus block the arteries supplying the placenta and provide a shearing force, removing the placenta from the wall of the uterus. Contractions push the placenta out of the birth canal |
| TRUE OR FALSE: endometrial epithelium recovers quickly after delivery of the placenta | TRUE |
| What are the effects of lactation? | Suppresses pituitary gonadotropins, returns uterus to pre-pregnancy size |
| What is the effect of progesterone on breast tissue? | Inc growth of the alveoli & lobules |
| What is the effect of estrogen on breast tissue? | Inc duct development |
| What is the effect of prolactin on breast tissue? | directs the production of milk within the alveolar cells |
| What is the effect of oxytocin on breast tissue? | In response to suckling, it stimulates myoepithelial cells of the alveoli to contract and release milk into the ducts |
| What inhibits milk release during pregnancy? | Progesterone and estrogen secreted by the placenta |
| What happens to levels of protesterone, estrogen, and prolactin at birth? | Progesterone and estrogen secretion stops, and prolactin levels greatly increase over the next few days |
| By when is the egg completely implanted into the wall of the uterus? | between day 9-16 (?) |
| By when are the major structure of the fetus formed? | By 13 weeks |
| Which pregnancy hormone do people use as an adjunct to exogenous testosterone? | HCG, which will enhance testosterone secretion of the host testis and attempt to avoid some of the adverse effects of exogenous testosterone use. |
Created by:
hclark86
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