Phys-fetal circulation

Question 1

Name the four anatomical shunts

Answer 1

1. Placental circulation (lungs, GI tract, kidneys)
2. Ductus arteriosus (bypasses lungs, connects pulmonary a. to descending aorta)
3. Ductus venosus (bypasses liver, connects umbilical v. to IVC)
4. Foramen ovale (bypasses RV and lungs, connects RA to LA)

Question 2

Placental has exchange is inefficient due to ___

Answer 2

Large diffusion distances

Question 3

PO2 for fetal umbilical v. blood is ___

Answer 3

~30 mmHg

*maternal is ~100mmHg

Question 4

How does the fetus compensate for the extremely low PO2?

Answer 4

1. Hemoglobin is ~50% more concentrated in the fetus (this increases oxygen content)
2. Fetal hemoglobin has a higher affinity for O2 (more O2 is carried per gram of hemoglobin)
3. Unloading of O2 is easier due to metabolites (Bohr effect)
4. Increase in placental cross sectional area, thinning of villar membranes (this enhances oxygen flux)

Question 5

At PO2, fetal hemoglobin is ___ saturated compared to ___ in adults

Answer 5

80%

50%

Question 6

What things are exchanged through passive diffusion in the placenta?

Answer 6

Fatty acids
Small ions such as Na, K, Cl
Waste products

Question 7

What things are exchanged through facilitated diffusion in the placenta?

Answer 7

Glucose (GLUT 1 and 3)

-not insulin dependent

Question 8

What things are exchanged through active transport in the placenta?

Answer 8

Amino acids
Ascorbic acid
Ca
Phosphate

Question 9

Fetus –> Newborn –> Adult

Change from circulation in ___ to ___

Answer 9

Parallel to series

Question 10

True or false:

The left ventricle alone supplies systemic circulation in the fetus

Answer 10

False

Both the left and right

Question 11

Left ventricular output is ___ of the CVO while the right is ___

Answer 11

1/3: (67% of this goes to the head, coronary arteries, upper limb, torso, 33% goes to lower body)
2/3: (10% goes to pulmonary circ, 90% crosses the ductus arteriosus to the descending aorta and goes to the abdomen Minaj organs, lower limbs, and placenta)

Question 12

True or false:

The right ventricular output is more highly oxygenated

Answer 12

False

The left is

Question 13

___ contain oxygenated blood leaving the placenta

Answer 13

Umbilical v.

Question 14

Highest oxygen sat in the fetus

Answer 14

80% in the umbilical v.

Question 15

Pressure in the ___ atrium is greater than the ___ because ___

Answer 15

Right
Left
Flow moves from right to left

Question 16

Larger stream (60%) from the ____ goes to the (RV/LV) and is (more/less) oxygenated. The smaller stream (40%) from the ____ goes to the (RV/LV) and is (more/less) oxygenated.

Answer 16

IVC-RV-less

Umbilical v.-LV-more

Question 17

Sources of RV blood

Answer 17

64% from IVC (lower body and placenta)
32% from SVC (upper torso and head)
4% from coronary sinus

Question 18

Sources of LV blood

Answer 18

79% from IVC (lower body and placenta)

21% from lungs

Question 19

The ___ contains the highest O2 sat in arterial circulation

Answer 19

LV at 62%

Question 20

Mean pressure in the pulmonary artery is ___ than that of the aorta because ___

Answer 20

Greater

Flow across the ductus arteriosus is from pulmonary a. to aorta (right to left)

Question 21

The starling mechanism is not well developed in the fetus, so increasing preload causes ___ while increasing afterload causes ___

Answer 21

Little increase in SV

Big decrease in SV

Question 22

Two main circulatory events occur at birth:

Answer 22

Parallel to series arrangement is facilitated by:

1. Pulmonary vasodilation leading to increased pulmonary blood flow
2. Cessation of flow in the umbilical arteries and vein

Question 23

In the fetus, pulmonary vascular resistance is ___ due to ___

Answer 23

High due to

Hypoxic vasoconstriction and physical compression of the collapsed lungs

Question 24

At birth, pulmonary vascular resistance ___ and this leads to ___

Answer 24

Falls

-increase in pulmonary blood flow, increase in left atrial pressure so foramen ovale closes

Question 25

At birth, umbilical vein ___ and flow in the ___ decreases so it closes in about ___

Answer 25

Constricts
Ductus venosus
1 week

Question 26

At birth, umbilical artery flow ___ and this causes ___

Answer 26

Ceases
Peripheral vascular resistance increases, aortic pressure becomes larger than pulmonary a. pressure, so ductus arteriosus closes