Duration = 10:18
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at co-educational topic number 8
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maternal fetal physiology this is the
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story of Peggy preggers and the
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physiologic changes that occur in her
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body throughout her pregnancy a lot
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happens to the female body in order to
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create a new human being the objectives
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of this video to discuss the maternal
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physiologic and anatomic changes
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associated with pregnancy describe fetal
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and placental physiology and lastly
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interpret common diagnostic studies
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during pregnancy there are a lot of
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changes that occur in each of the three
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trimesters of pregnancy remember that we
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use menstrual dating when calculating
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the weeks here is our trusty pregnancy
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wheel and from the first day of her last
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menstrual period we calculate the
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estimated date of delivery or EDD as 40
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weeks after the LMP so the first
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trimester is approximately zero to
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thirteen weeks the second trimester is
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approximately 14 or 27 weeks and the
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third trimester is approximately 28 to
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40 weeks we will discuss changes in the
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pregnant body by system and how these
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changes occur in the three different try
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Buster’s there are changes in thyroid
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regulation during pregnancy remember
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that beta HCG levels peak at a hundred
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thousand around ten weeks and then come
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down to about ten thousand at term beta
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HCG has thyrotropin like activity and
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this stimulates maternal thyroxine or t4
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secretion and thus produces a transient
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rise in free t4 levels in the first
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trimester as beta HCG levels decline
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free t4 levels decline to normal
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concentrations rising levels of estrogen
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and pregnancy caused an increase in
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thyroxine binding globulin which results
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in increased levels of total t4 and
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total t3 but levels of free t4 and free
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t3 are unchanged from the normal range
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let’s now move to the GI system here is
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Peggy in her first trimester with her
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small developing pregnancy and her
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corpus luteum is making large volumes of
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progesterone as the pregnancy progresses
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past the first trimester the placenta
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will take over as the main source of
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progesterone production progesterone
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relaxes smooth muscles throughout the
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body and in the GI system the
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progesterone will relax the lower
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esophageal sphincter tone which can
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result in gastroesophageal reflux
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disease or GERD progesterone also
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reduces gallbladder contractility which
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leads to an increased prevalence of
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gallstone
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progesterone also decreases GI motility
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which can cause constipation in the
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first trimester many women experience
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nausea and vomiting
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the term morning sickness is not very
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accurate for many women experience it
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throughout the day approximately fifty
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to ninety percent of women experience
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nausea and vomiting in the first
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trimester the cause is unknown but is
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thought to be related to elevated levels
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of progesterone and beta HCG severe
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nausea and vomiting and pregnancy is
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referred to as hyperemesis gravidarum
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and can result in significant weight
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loss Keeton emia and electrolyte
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imbalance in the second trimester as the
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beta HCG levels decline nausea and
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vomiting tends to improve and for most
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women it is abated by about 14 to 16
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weeks as the uterus grows throughout the
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second and third trimester the stomach
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is physically displaced upwards by the
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growing uterus and this also contributes
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to GERD during pregnancy let’s move now
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to the cardiovascular system the female
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body essentially needs more volume to
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support the growing pregnancy the
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circulating blood volume begins
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increasing by week six eight and reaches
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a peak increase of forty-five percent by
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32 weeks the heart essentially needs to
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work harder during pregnancy cardiac
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output increases by 30 to 50 percent
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with 50 percent of that increase
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occurring by eight weeks
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remember that cardiac output equals
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heart rate times stroke volume in the
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first half of pregnancy
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cardiac output increases are secondary
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to increase stroke volume in the second
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half of pregnancy cardiac output
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increases are secondary to increased
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heart rate there is a decrease in blood
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pressure during pregnancy secondary to
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progesterone smooth muscle relaxing
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effects and increase production of azo
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dilatory substances from the growing
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placenta supine postural hypotension
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syndrome refers to the hypotension that
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pregnant women experience when laying
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flat on their backs late in pregnancy as
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the uterus grows it can impede the vena
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cava
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when a woman is supine this is why we
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advise women not to lay flat on their
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backs while sleeping and instead
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recommend sleeping with a left tilt or
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on their side and remember as a uterus
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grows it gets more of cardiac output so
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by the end of pregnancy it gets 20% of
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cardiac output as opposed to 2% of
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cardiac output in the first trimester
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moving on to the respiratory system
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oxygen consumption increases during
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pregnancy
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minute ventilation which is defined as
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the volume of air that is taken in every
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minute increases by 30 to 40 percent
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this increase in ventilation results in
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increased production of co2 which
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results in a reduction of arterial pco2
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or a development of a respiratory
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alkalosis this is balanced by the kidney
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excreting more bicarbonate which yields
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the lower bicarbonate levels seen in
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pregnancy an arterial blood gas in
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pregnancy will show a compensated
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respiratory alkalosis with a normal pH
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the maternal thorax undergoes several
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morphological changes during pregnancy
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the diaphragm is elevated and impressive
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four centimeters by late pregnancy due
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to the gravity uterus in addition the
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sub costal angle widens as the chest
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diameter and circumference increased
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slightly moving on to the hematologic
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system remember that the circulating
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volume increases by 45 to 50 percent by
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the third trimester of pregnancy the red
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cell volume also increases although to a
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lesser extent than the plasma volume the
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maternal blood volume increases by 35%
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at term this creates a physiologic
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anemia at term the average hemoglobin
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concentration is 12.5 compared to 14 in
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the non pregnant State supplemental iron
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during pregnancy is thus intended to
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prevent further iron deficiency the
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concentration of different clotting
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factors change during pregnancy
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fibrinogen levels increased by 50%
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protein C and protein s levels decrease
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and the risk of thromboembolism doubles
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during pregnancy and increases to 5.5
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times the normal risk during the
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immediate postpartum time how do all of
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these changes manifest on examination of
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pecky preggers first expect to see low
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blood pressures blood pressure start to
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decline by week 7 and reach a maximal
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decline by weeks 24 to 26 weeks it is
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also common to see distended neck veins
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from the increased volume of pregnancy
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pregnant women often also have a
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low-grade systolic ejection murmur
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secondary to increase flow across the
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aortic and pulmonic valves note a
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diastolic murmur is not normal in
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pregnancy and should be evaluated let’s
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now switch gears and discuss fetal and
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placental physiology here is a
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cross-section of the umbilical cord with
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two umbilical arteries and one umbilical
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vein
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remember that blood flows from the
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umbilical vein
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to the fetus and then from the fetus
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through the two umbilical arteries so
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blood flows from the umbilical vein to
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the portal system and here 50% of the
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blood goes to the right lobe of the
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liver and 50% of the blood goes through
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this first shunt to pregnancy called the
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ductus venosus into the inferior vena
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cava
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here’s blood going through the ductus
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venosus into the inferior vena cava
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there the blood travels to the right
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atrium so here is the heart with the
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right atrium the right ventricle the
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left atrium and the left ventricle the
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second shunt of pregnancy is the foramen
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ovale and some of the blood will go from
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the right atrium to the left atrium to
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the left ventricle and then into the
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aorta some blood goes from the right
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atrium to the right ventricle and then
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into the pulmonary arteries the third
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shunt of pregnancy is the ductus
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arteriosus so blood will go from the
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pulmonary arteries through this ductus
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arteriosus into the aorta the blood then
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goes from the aorta down to the common
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le X and then from the common iliac
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there are the internal iliac s– which
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then branch to the umbilical arteries
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back to the placenta so remember that it
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is oxygenated blood that flows from the
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umbilical vein I’m going to represent
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this in red it goes from the umbilical
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vein through the first shunt of the
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ductus venosus up through the second
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shunt of the foramen ovale and then
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through the third shunt of the ductus
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arteriosus I’m gonna represent the blood
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flow now in purple to represent that
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it’s mixing with the oxygenated blood
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and at the end of the circuit I’ll
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change to blue to represent the fully
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deoxygenated blood what happens in the
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placenta
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here’s the umbilical cord and then here
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is the placenta the placenta is a unique
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organ of pregnancy for it is partially
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fetal and partially maternal we’ll call
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this top part the fetal portion and the
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bottom portion the maternal portion the
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simplest way to think about this system
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is that the placenta has pools of
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maternal blood so here are the pools of
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maternal blood and the fetus inserts its
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capillaries into these pools of maternal
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blood trophoblastic cells help with this
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invasion process it is at these sites of
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intersection of fetal and maternal
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tissues that oxygen and excretion of co2
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cross the placenta by simple diffusion
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glucose and amino acids are other
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solutes that are transferred from the
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mother to the fetus at these sites thus
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we conclude the video about Peggy
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preggers and the amazing changes that
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occur throughout the three trimesters of
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her pregnancy we have discussed the
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maternal physiologic and anatomic
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changes associated with pregnancy
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The Associated physical exam and
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diagnostic study changes during this
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time as well as fetal and placental
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physiology
English (auto-generated)