Uteroplacenta and Fetal Physiology

umbilical arteries -how many? -what kind of blood?path? -branches from what? -what doe they feed?

-2 arteries/paired -carries deoxygenated blood from fetus to placenta -branches of the fetal internal iliac arteries -feed placental villi

Double Bohr Effect

-CO2 transfer b/t mom and fetus makes maternal blood more acidic and fetal blood more alkalotic -changes in pH cause shifts in maternal/fetal oxyHb dissociation curves -allows maternal O2 transfer to fetus

umbilical vein

-carries oxygenated blood from placenta -travels through liver and joins the hepatic vein/IVC→ RA

-what type of alveoli produce surfactant? -at what gestation are these alveoli formed? -at what gestation does surfactant production begin?

-cuboidal alveoli -30weeks -34weeks

what can cause ↑ uterine vascular resistance? (↑uterine vascular resistance= ↓UBF)

-endogenous vasoconstrictors: catecholamines from stress, vasopression -exogenous catecholamine: epi, phenylephrin> ephedrine, high concentration LA

During gestation there is an "invasion" of ______________ arteries into the uterus which leads to ____________ of arterial ____________ __________ and loss of _______________ ability of the vessels

-spiral -loss -smooth muscle -contractile

what can cause ↓ uterine arterial pressure? (↓uterine arterial pressure = ↓ UBF)

-supine position -hemorrhage/hypovolemia -sympathetic blockade→ hypotension (spinal/epidural)

what can cause ↑ uterine venous pressure? (↑uterine venous pressure = ↓UBF)

-supine position (blocked outflow of IVC) -uterine contractions (↑intrauterine pressure) -cocaine -pushing during labor -seizures -pitocin/oxytocin (multiple contractions)

ovarian arteries: -what do they supply? -brach of what artery? -what % of BF? -where do they end?

-supply uterus -branch of abdominal aorta, below the renal artery -15% of BF to uterus -end in spiral arteries

uterine arteries: -what do they supply/ -branches of what artery? aka? -equal BF? -what % of blood flow? -where do they end?

-supply uterus -branches of anterior devision of the internal iliac artery (aka hypogastric artery) -whatever side of the uterus the placenta is embedded on will have more BF than the opposite side -85% of BF t -ends in spiral arteries

Passive transport depends on what 6 things?

1. concentration gradient 2. electrochemical gradient 3. molecular weight 4. libid solubility 5. degree of ionization 6. membrane surface area/thickness

vital functions of amniotic fluid (3)

1. facilitates fetal growth 2. cushion for fetus, allows for movement 3. defense mechanism

3 anatomic communications in fetal circulation? where are they located?

1. foramen ovale (between RA and LA) 2. ductus arteriosus (between PA and aorta) 3. ductus venosus (connects umbilical vein to hepatic vein/IVC)

primary causes of respiratory effort in a newborn?

1. hypoxia 2. acidosis 3. sensory stimulation (cord clamping, noise, pain, touch)

4 functions of placenta **IMPORTANT

1. link between mother and fetus 2. respiratory gas exchange 3. nutrient/drug transfer 4. waste exchange

6 factors that influence maternal/fetal exchange (not the same as the factors that influence transfer of medications between mother/fetus)

1. maternal and fetal blood flow 2. placental binding 3. placenta metabolism 4. diffusion capacity of what needs to cross 5. protein binding 6. gestational age

the transport of medications from mother to fetus depends on what 6 things?

1. maternal drug concentraion 2. membrane barrier to diffusion 3. placental anatomy 4. protein binding 5. uterine perfusion 6. fetal blood concentration (saying to help remember: maternal membranes place protein under flowers???)

O2 transfer across the placenta depends on what 5 factors?

1. membrane surface area 2. membrane thickness 3. partial pressure of P2 gradient between maternal/fetal blood 4. affinity of maternal and fetal Hb 5. blood flow between mother and fetus

causes of increased uterine blood flow (4)

1. neuraxial anesthetic (↓ vascular resistance) 2. treatment of chronic HTN (= increased UBF) 3. vascular remodeling of arteries= ↑vessel length, ↑ vessel diameter= ↓arterial resistance 4. ↓blood viscosity (minor ↑UBF)

4 transfer mechanisms (+1 that was not listed)

1. passive transport 2. facilitaed transport (glucose) 3. active transport (NaK ATP) 4. pinocytosis (+phagocytosis)

3 sets of arteries that supply the uterus with blood flow

1. uterine arteries (85%) 2. ovarian arteries (15%) 3. spiral arteries (deliver to intravilla space)

causes of decreased uterine blood flow (3)

1. ↓uterine arterial pressure 2. ↑uterine venous pressure 3. ↑uterine vascular resistance

umbilical blood flow at term what does regulation depend on?

100-120ml/kg/min regulation dependent on fetal catecholamines

irreversible fetal brain damage r/t hypoxemia occurs in about how many minutes?

10minutes

fetal Hb

17g/dl

3 vessels in umbilical cord - what type of blood does each carry?

2 umbilical arteries -carries deoxygentaed blood 1 umbilical vein -carries oxygenated blood

at what gestation do true alveoli develop/form?

36weeks

how many ml of reserve O2 does the fetus have?

42ml

what % of blood goes from RV to pulmonary circulation?

5%

uterine BF at baseline (non-pregnant)? uterine BF at term gestation? what % of maternal CO is this?

50-100ml/min 700-900ml/min 20% of CO

weight of placenta at term

500g

SpO2 of blood from placenta

80%

what molecular weight can pass the across the placenta via passive transport?

<600 daltons

oligohydramnios

AFI <5-6 cm (normal 8-18) **too little fluid

polyhydramnios

AFI > 20-24cm (normal 8-18) **too much fluid

AFI- - what does it stand for and what does it estimate? what is normal?

AFI= Amniotic Fluid Index -estimates amniotic fluid volume normal: 8-18cm

what changes from fetal life to neonate life are considered to be the most profound ?

CV and respiratory **if these do not transition, there is a potential for death or permanent neuro damage

does fetus depend on mother for thermoregulation? what happens if there is ↓UBF?

NO -fetus produces 2x as much heat as mom (0.5degrees C higher than mom) ↓UBF= ↑ fetal temperature

RV and LV dont have an equal EF during fetal circulation... what fraction of blood do each eject?

RV: 2/3 LV: 1/3

does the uterus autoregulate?

YES when NOT pregnant NO AUTOREGULATION WHEN PREGNANT **therefore maternal BP is CRITICAL

if mom goes into labor earlier than 34weeks, what drug is given to encourage the development of surfactant in the fetus?

betamethasone (dose once then 24h later= total of 2 doses)

what is a major determinant of transfer of CO2 between mom and fetus?

concentration gradient

where do spiral arteries deliver blood to? for what?

deliver blood to intra-villa space where nutrient, gas, and drug exchange happens

flow of deoxygenated blood from lower extremities and SVC

deoxygenated blood from IVC & SVC→ RA→ RV→ PA→ PDA→ descending aorta→ lower extremities **PDA shunts blood away from the lungs and into the aorta **blood flow from the lower extremities returns to heart via IVC OR goes back to placenta via umbilical arteries

is the placenta more permeable or less permeable in early gestation compared to late gestation?

early= more permeable late= less permeable

how is glucose transported?

facilitated transport

what transfer mechanism is noted for saturation kinetics?

facilitated transport *there is a v-max, once v-max is reached, transport doesnt happen any faster

chorionic plate

fetal side of placenta

P50 for fetal Hb vs P50 of maternal Hb

fetal: 18-19mmHg maternal: 27-30mmHg **fetal Hb has a higher affinity for O2, therefore a lower P50

fetal O2 demand adult O2 demand

fetal: 8ml/min/kg adult: 3-4ml/min/kg

how does fetus get glucose?

fetus is dependent on placental transfer from mother for all of glucose

what crosses membranes via facilitated transport? what happens when there is a higher temperature?

glucose higher temperatures will increase transfer of the agent/ion

uterus blood flow: ____________ flow through ____________ resistance circuit

high low

what is hyperemia and when does it occur during labor?

hyperemia= rapid BF back to area happens when uterus relaxes during labor-- there is ↑ perfusion every time the uterus relaxes

70-90% of uterine blood flow passes through what space? what does the remainder of BF supply?

intervillous space remainder supples myometrium/muscle of uterus

what is the space called where blood flows to allow for exchange of nutrients, gas, drugs, waste, etc.?

intervillous space terminla villi: where blood goes for exchange

relationship between UBF in labor and contraction strength relationship between UBF in labor and intrauterine pressure

inverse inverse **stronger contraction= ↓ UBF because of ↑ intrauterine pressure

basal plate

maternal side of placenta

does fetal pulmonary and systemic circulation run in sequence or parallel?

parallel

what branch of the nervous system appears first?

parasympathetic -becomes more dominant throughout pregnancy -responsible for lower HR at term than earlier in gestation

hypoxia, acidosis, hypovolemia and hypothermia may lead to prevention/reversal of circulatory change at brith which can lead to what condition? -this can become a vicious cycle because it can lead to ____ to ____ shunting, therefore causing more acidosis and hypoxia

persistant pulmonary hypertension of the newborn right to left shunting

flow of oxygenated blood from placenta

placenta→ umbilical vein→ ductus venosus→ IVC→ RA→ foramen ovale→ LA→ LV→ aorta→ upper body **30-50% (20% at term) of oxygenated blood from placenta bypasses portal circulation and goes directly into IVC

Le Chatelier's Principle

rapid movement of CO2 from fetal capillary blood to maternal blood, causing a shift in the equilibrium of the carbonic anhydrase reaction which produces more CO2 for diffusion

Oxyhemoglobin curves: maternal Hb: ______ shift fetal Hb: _______ shift

right left

s/s of persistent pulmonary hypertension of the newborns? baby has an increased incidence of developing this if mom takes what medications?

s/s: -cyanosis -high O2 requirement ↑incidence: -SSRIs -NSAiDS **can lead to premature closure of PDA

what is pinocytosis? does it require energy?

transfer of large macromolecules (cell membrane invaginates the molecule and brings it in) -yes, requires energy

what arteries are often targeted for embolization when there is post-partum hemorrhage?

uterine and ovarian

______________ _____________ _____________ is one of the most important determinants of __________________ maternal/fetal exchange

uterine blood flow successful

Uterine blood flow equation

uterine perfusion pressure/ uterine vascular resistance **uterine perfusion pressure= difference between uterine arterial and venous pressures

what veins drain blood from uterus?

uterine veins

in fetal circulation, if hypoxia is encountered, _________________ is released which causes vasoconstriction and shunts blood flow to ________________ and ______________

vasopressin brain heart

what causes closure of the foramen ovale?

↑ pulmonary blood flow→ ↑LA pressure → closure of foramen ovale

what causes functional closure of the PDA? when does anatomic closure occur?

↑O2 tension→ contraction of PDA anatomic closure in 2-3weeks after delivery

increased UBF: ___ vascular resistance ___ intravascular volume ___ CO (increased or decreased)

↓vascular resistance ↑intravascular volume ↑CO

what transport mechanism requires cellular energy and can allow a substance to move against its gradient? ... what does it require to do this? ... example?

active transport -requires protein membrane carrier -ex: NaK ATP pump