test 3 part 2

Question 1

In the fetus, some organs do not function until birth

Answer 1

 Lungs
 Kidneys
 GI Tract

Question 2

Fetus obtains oxygen and nutrients via

Answer 2

 diffusion from the

maternal blood.

Question 3

Wastes and CO2 are eliminated via

Answer 3

 diffusion into the maternal blood
 Exchange occurs via the placenta
 Inside the uterus
 Attached to baby via the umbilical cord

Question 4

Umbilical Artery

Answer 4

 carries deoxygenated blood AWAY from the fetus to the placenta
 Carries wastes and CO2
 LOW O2 Content!

Question 5

Umbilical Vein

Answer 5

 carries oxygenated blood from the placenta to the fetus
 Carries nutrients and O2
 HIGH O2 Content

Question 6

Fetal Capillaries

Answer 6

 Umbilical arteries and veins branch into these capillaries located inside the intervillous spaces in the placenta.

Question 7

Intervillous Spaces

Answer 7

 Spaces filled with maternal blood from uterine arterioles. Drained by Uterine veins.

Question 8

The Placenta

Answer 8

 The placenta communicates with the mother’s cardiovascular system via uterine blood vessels.
 Wastes diffuse out of the capillaries into the intervillous spaces containing maternal blood in the placenta.
 Nutrients travel from mother’s blood vessels to the intervillous space via uterine arteries.
 Diffuse from the intervillous spaces into the fetal capillaries
 The concentration of hemoglobin in fetal blood is about 50% higher than maternal blood
 Fetal hemoglobin has a greater affinity for oxygen than maternal blood
 Can carry 30-35% more oxygen.
 THERE IS NO DIRECT MIXING OF MATERNAL AND FETAL BLOOD!!!

Question 9

The Placenta - Function

Answer 9

 Exchange of gases – CO2, O2, CO
 Accomplished via diffusion
 20-30mL O2/min extracted
 Short interruption in blood flow can be fatal to fetus
 Depends on delivery not rate of diffusion
 Exchange Nutrients/ Electrolytes
 Amino Acids, Free Fatty Acids, Carbohydrates, Vitamins
 Exchange is rapid and increases as pregnancy increases
 Placental circulation has a very low resistance (They flow into pools)
 Transfer of Maternal Antibodies
Immunoglobulins – Primarily IgG transported from mother to fetus providing passive immunity
Newborns produce own IgG, but don’t reach adult levels until about age 3 (get antibodies from breast milk)
 Hormone Production

Question 10

Umbilical Blood Vessels

Answer 10

 Blood passes from the fetus to the placenta via 2 umbilical arteries
 Branch of the internal iliac arteries
 Sat ~58%
 Oxygenated blood (sat ~80%) returns from the placenta via 1 umbilical vein
 Goes to the liver of the fetus where it divides into 2 branches
 Joins hepatic portal vein -> Liver (1/3)
 Ductus Venosus -> IVC (2/3)
 Sphincter mechanism in ductus that controls blood flow through the liver
 In the IVC, oxygenated blood via the ductus venosus meets deoxygenated blood from the lower body
 Sat falls to about 67%

Question 11

Fetal Lungs

Answer 11

 Filled with fetal lung fluid
Not used to oxygenate blood
 This liquid increases the pulmonary vascular resistance to blood flow

Question 12

Most fetal blood does not go from the RV to the lungs

Answer 12

 Instead, it passes through the Foramen Ovale
 Hole between the Right and Left Atria.
 Blood entering from the IVC is guided toward the foramen ovale to the Left Atrium.
 In the LA, blood mixes with the very small amount of blood returning from the pulmonary veins
 Goes to the LV
 LV pumps the oxygenated blood into the aorta
 Perfuses the brain and myocardium
 Getting highest O2 content available

Question 13

Fetal blood returning to the heart from the SVC

Answer 13

 bypasses the Foramen Ovale and enters the RA
 Goes to the RV and pumped to the PA
 Pulmonary Vascular Resistance is so high that 95% of this blood bypasses the pulmonary arteries
 Travels across the ductus arteriosus to the descending aorta
 Ductus arteriosus connects PA and Aorta
 Perfuses fetal tissues

Question 14

At the common iliac branch to the internal and external iliacs

Answer 14

 Part of that blood flowing systemically will flow through the internal iliacs to the umbilical artery
 Will go to the placenta for nutrient/waste exchange
 The only fetal vessel to carry fully oxygenated blood is the umbilical vein
 Blood entering the aorta from the LV and perfusing the head and heart has a higher oxygen content than the blood perfusing the rest of the body.

Question 15

Transition to Neonatal Circulation

Answer 15

 At birth, the Pulmonary, Renal and Digestive Systems start to function.
 There are 3 shunts present in the fetal circulation that normally close after birth:
 Ductus Arteriosus
 Foramen Ovale
 Ductus Venosus

Question 16

Neonatal Umbilical Arteries

Answer 16

 Contraction of smooth muscle in walls
 Likely caused by thermal and mechanical stimuli and change in oxygen tension
 Functionally close a few minutes after birth
 Eventually will fill with connective tissue
 Distal portion will become fibrous cords
 Medial umbilical ligaments
 Functionally closed after birth
 Complete closure takes 2-3 months.

Question 17

Neonatal Umbilical Vein

Answer 17

 Collapses shortly after the umbilical arteries
 Blood from the placenta may enter newborn for some time after birth.
 Remains as the ligamentum teres hepatis
 Lower margin of the falciform ligament. Attaches the umbilicus to the liver

Question 18

Neonatal Ductus Venosus

Answer 18

 Collapses
 Remains as Ligamentum Venosum
 Fibrous cord on the inferior surface of the liver
 Patent Ductus Venosus is extremely rare
 Less than 20 reported world wide

Question 19

Neonatal Foramen Ovale

Answer 19

 Usually closes after birth to become the Fossa Ovalis
 The first breath causes the lungs to expand and blood flow to the lungs increases.
 Blood returning to the LA increases the pressure in the LA
 And pressure in the RA falls.
 First breath presses the septum primum against the septum secundum
 causes functional closure of the foramen ovale at birth.
 First days of life, closure is reversible
 Crying by baby creates a right to left shunt and can account for the cyanotic periods of newborns.
 Constant apposition leads to fusion of the septa.
 Anatomical (permanent) closure occurs within the first year of life.

Question 20

Neonatal Circulation - PFO

Answer 20

 After a year, if the Foramen Ovale has not closed, it is referred to as a Patent Foramen Ovale (PFO).
 Autopsy studies show a 27% prevalence of PFO
 Most patients are asymptomatic

Question 21

Neonatal Ductus Arteriosus

Answer 21

 Closes via contraction of the muscular wall immediately after birth.
 Mediated by Bradykinin which is released by the lungs during the initial inflation.
 After the first breath, the lungs fill with air instead of fluid
 Pulmonary vascular resistance falls
 Pulmonary blood flow increases
 Ductus initially protects the pulmonary vasculature from overload.
 Ductus Arteriosus starts to close via vasoconstriction immediately after birth.
 Takes about 1-2 days to close in a full term infant
 Small shunt of blood from the Aorta to the left PA for a few days
 Becomes the Ligamentum Arteriosum
 Complete obliteration of the lumen takes 1-3 months