10.5 Fetal Circulation

Question 1

Why are all the circulatory features present in the fetus and not in the adult necessary?

Answer 1

the fetus does not use its lungs for gas exchange

Question 2

What happens to much of the blood entering the right atrium in the fetal circulation?

Answer 2

it is shunted into the left atrium through the FORAMEN OVALE between the two atria

Question 3

What is the foramen ovale?

Answer 3

the flap dividing the left atrium from the right atrium of the heart

Question 4

What happens to any blood that does enters the right ventricle and is pumped into the pulmonary trunk?

Answer 4

it’s shunted into the aorta by way of the ductus arteriosus

Question 5

What is the ductus arteriosus?

Answer 5

structure of the heart associated with fetal circulation and provides a pathway for returning any blood that enters the right ventricle back to the aorta

Question 6

Where does the blood within the aorta travel?

Answer 6

to various branches, including the iliac arteries

Question 7

What do the iliac arteries do?

Answer 7

connect the umbilical arteries leading to the placenta

Question 8

What occurs at the placenta?

Answer 8

exchange of gases and nutrients between maternal blood and fetal blood

Question 9

What does the umbilical veins do?

Answer 9

carries blood that’s rich in nutrients and oxygen to the fetus

enters the liver and joins the ductus venosus which merges with the inferior vena cava

Question 10

Where are the umbilical arteries and vein?

Answer 10

they run alongside one another in the umbilical cord which is tied off and cut at birth, leaving only the umbilicus (navel)

Question 11

What is the most common cardiac defect in a newborn? What happens?

Answer 11

the persistence of the foramen ovale

• once the umbilical cord has been severed and the lungs have expanded, blood enters the lungs in quantity
• the return of this blood to the left side of the heart usually causes a flap to cover the opening
• incomplete closure occurs in nearly 1/4 individuals

Question 12

Why does passage of blood from the right atrium to the left atrium rarely occur?

Answer 12

either the opening is small or it closes when the atria contract

Question 13

What is “blue baby”?

Answer 13

the passage of impure blood from the right side to the left side of the heart is sufficient to cause a “blue baby”

Question 14

How can “blue baby” be corrected?

Answer 14

by threading a catheter into the heart and sealing the defect

Question 15

What is the placenta?

Answer 15

structure that only functions before birth

• when the child is born, the placenta becomes part of the afterbirth

Question 16

Where is the placenta?

Answer 16

firmly attached to the uterine wall by the allantois and by fingerlike projections called the chorionic villi

Question 17

What does the placenta do?

Answer 17

functions in gas, nutrient, and wast exchange between the embryonic (later fetal) and maternal circulatory systems

Question 18

Where is the umbilical cord?

Answer 18

stretches between the placenta and the fetus

Question 19

Why is the umbilical cord the lifeline of the fetus?

Answer 19

it contains the umbilical arteries and vein which transport waste molecules (carbon dioxide and urea) to the placenta for disposal and take oxygen and nutrient molecules from the placenta to the rest of the fetal circulation system

Question 20

Why does the ductus arteriosus normally close?

Answer 20

endothelial cells divide and block off this duct

Question 21

What later transforms into connective tissue?

Answer 21

remains of the ductus arteriosus and part of the umbilical vein