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Phys Spring 5: Lec 3

Pregnancy & Lactation

QuestionAnswer
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