fetal circulation 4

Question 1

What are the four shunts in the fetal circulation?

Answer 1

1. ductus venosus
2. foramen ovale
3. ductus arteriosus
4. hypogastric arteries –> umbilical arteries

Question 2

What organ does the blood bypass when it flows through the ductus venosus?

Answer 2

the liver

Question 3

What percent of blood passes through the foramen ovale?

Answer 3

40%

Question 4

What mantains the ductus arteriosus patent?

Answer 4

prostaglandin E2

Question 5

What organ does blood bypass when it flows through the ductus arteriosus?

Answer 5

the lungs

Question 6

Output from the ventricle in the fetus is in parallel or series?

Answer 6

parallel

series in an adult

Question 7

What are the two sources of pulmonary resistance in the fetus?

Answer 7

hypoxia

lung deflation

Question 8

Where is the highest and where is the lowest o2 saturation in the fetus?

Answer 8

highest - umbilical vein

lowest - umbilical arteries

Question 9

What triggers the first breath?

Answer 9

mild hypoxia, hypercapnia, tactile stimuli, cold skin

Question 10

What type of pneumocyte produces surfactant?

Answer 10

type II

Question 11

In the fetus are these parameters high or low?

• vascular resistance
• pulmonary blood flow
• MAP

what happens to each at birth?

Answer 11

1. vascular resistance - high
2. pulmonary blood flow - low
3. MAP - high

these all reverse at birth

Question 12

What four organs (systems) does the placenta simulate in the fetus?

Answer 12

Lungs, GI tract, liver, kidneys

Question 13

When does the fetal heart begin to beat? What is the normal rate?

Answer 13

one month after fertilization

65-140 bpm

Question 14

When are all the organs in the fetus formed?

Answer 14

at one month

Question 15

What percent of the sum of the output from the left and right ventricles does the placenta receive?

Answer 15

50%

Question 16

Closure of the placental circulation at birth has what affect on peripheral resistance?

Answer 16

causes it to double

Question 17

What causes the closure of the foramen ovale?

Answer 17

reversal of right and left atrial pressure

• due to increased pulmonary circulation to Left atrium
• decrease in right atrial pressure

Question 18

Closure of the ductus venosus allows what to organ to be perfused?

Answer 18

portal blood perfuses the liver

Question 19

What mechanism accounts for the transition of the ductus venosus –> ligamentum venosum?

Answer 19

increased PO2 and reduced prostaglandins

Question 20

If the ductus venosus does not close, what will occur?

Answer 20

portosystemic shunt

Question 21

What are some possible symptoms of a patent ductus arteriosus?

Answer 21

pulmonary hypertension
possible congestive heart failure
cardiac arrythmias
risk of endocarditis

Question 22

Does pulmonary vascular resistance increase or decrease upon birth?

Answer 22

decreases!

Question 23

What is coarctation of the aorta?

Answer 23

smooth muscle of the ductus arteriosus invades the descending aorta and constricts it following birth

-high BP above constriction

Question 24

What is the most common type of congenital defect?

Answer 24

ventricular septal defects

Question 25

What results from a large ventricular septal defect?

Answer 25

congestive heart failure ( blood is flowing from left to right)

Question 26

What can result from a large atrial septal defect?

Answer 26

pulmonary hypertension, right heart enlargement

blood flows from left atria to right atria

Question 27

What are the four hallmarks of tetralogy of fallot?

Answer 27

1. pulmonary stenosis
2. dextroposition of the aorta - overrides ventricular septum
3. right ventricular hypertrophy
4. ventricular septal defect