Fetal Circulation

Question 1

High blood flow to lung is NOT required during gestation

True or false?

Answer 1

True

Question 2

Blood is diverted from the fetal lung by the

Answer 2

Ductus arteriosus

Question 3

Dilation of the lung blood vessels is inhibited by

Answer 3

suppressing Nitric Oxide (NO) production in the vessels.

Question 4

Characteristics of fetal lung

Answer 4

• Increase resistance from low oxygen tension
• Low pulmonary blood flow
• Contracted blood vessels

Question 5

How much oxygen is in the placental blood?

Answer 5

80%

Question 6

Blood doesn’t go in the fetal lung cause?

Answer 6

Lungs are not working and are just growing and developing

Question 7

How does oxygen enter the fetus?

Answer 7

• Enters through the umbilical vein, travels through the liver via Ductus venosus
• Moves into right atria from the inferior vena cava and moves into the left atria through the Foramen Ovale (FO)
• High pressure to low pressure

Question 8

How does deoxygenated blood exit the fetus?

Answer 8

• Deoxygenated blood comes in to the right atria via the superior vena cava.
• Blood diverted from the lungs into the descending aorta by the Ductus Arteriosus
• Blood returns to the placenta via the Umbilical Arteries

Question 9

Blood returning to the placenta via the Umbilical Arteries is ?

Answer 9

58% oxygenated

Question 10

Fetal system has points where blood is mixed or diverted:

Answer 10

Liver

Inferior vena cava (IVC)

Right atrium (RA)

Left Atrium (LA)

Ductus arteriosus

Question 11

What happens at the Liver in the fetal system?

Answer 11

blood from the portal system mixes with umbilical blood

Question 12

What happens in the IVC in the fetal system?

Answer 12

Returning blood from the legs, pelvis and kidneys

Question 13

What happens in the RA in the fetal system?

Answer 13

deoxygenated blood from head and upper limb, mixes with oxygenated blood from placenta

Question 14

What happens in the LA in the fetal system ?

Answer 14

deoxygenated blood enters from the lungs

Question 15

What happens at the Ductus arteriosus in the fetal system?

Answer 15

diverts blood away from lungs to the descending aorta

Question 16

What happens during labours at the Ductus venosus?

Answer 16

Contractions close off the ductus venosus via a sphincter.

Question 17

Why is the Ductus venosus closed during labour?

Answer 17

Protection of fetus

Question 18

What happens during the first breath?

Answer 18

• Increase of surface area for gas exchange as lungs inflate
• Decrease of Pulmonary vascular resistance as bradykinin dilates blood vessels
• Increase lung blood flow.

Question 19

What stimulates the contraction of umbilical arteries?

Answer 19

Oxygenated blood and temperature change

Question 20

Placental blood flow stops at?

Answer 20

3-5 minutes

Question 21

Maintaining placental blood flow does what?

Answer 21

Maintaining blood flow for this period ( 3-5 minutes) increases juvenile jaundice but increases iron levels and prevents iron level drop at 4-6 months.

Question 22

Posta al changes

Answer 22

• Umbilical vein closes and becomes Ligamentum Teres
• Foramen Ovale closes and fuses
• Ductus Arteriosus closes becomes smaller
• Umbilical arteries close and become Medial Umbilical Ligaments

Question 23

What is the purpose of postnatal changes ?

Answer 23

This stops mixing of blood and separates the pulmonary and systemic circuits

Question 24

Function of Foramen ovale before birth

Answer 24

LA BP is lower so blood travels from R To L

Question 25

Effects of Ductus arteriosus closure in Foramen ovalis

Answer 25

- Increases lung circulation and increases the pressure in the LA - Increased pressure pushes the septum primum against the secundum, closing the Foramen ovalis - Septum primum and secundum (from opposing ends of the atria) close and fuse over a period of a few days.

Question 26

Steps of Ductus arteriosus closure

Answer 26

1. Breath 2. Lung expansion 3. Pulmonary vessel expansion 4. Decreased P in pulmonary vessel 5. Blood flow to lung 6. Bradykinin release 7. Muscular contraction 8. DA closure

Question 27

Bradykinin release causes?

Answer 27

Muscular contraction which closes DA

Question 28

Foramen Ovale- closure is reversible for first few days, until the tissue fuses True or false

Answer 28

True

Question 29

Closure of Foramen Ovale is reversible for first few days, Why?

Answer 29

Crying and dehydration- cyanotic (blue tinge to skin) periods Crying INCREASES pulmonary vascular resistance, decreases blood supply to the lungs

Question 30

Symptoms of Persistent cyanosis

Answer 30

fingers, lips, general pallor

Question 31

Symptoms of Patent DA

Answer 31

minimal symptoms at birth. •Distinctive heart murmur may be detected. •Low weight gain and breathing difficulties (apnoea) Patent DA may actually help in some cases ie transposition of great vessels