Congenital Abnormalities

Question 1

In utero

Answer 1

Lungs full of liquid, O2 supply is from

• Placenta
• umbilical Vein
• Shunts past liver via ductus venosus
• Bulk of blood heads to IVC of utero

then normally it would head from right side to lungs BUT it is already oxygenated, so instead it bypasses lungs via foramen ovale, from RA to LA.

**~25% blood does get to RV to pulmonary trunk, and the third shunt ductus arteriosus bypasses lungs again fromPT to aorta

Question 2

Foramen Ovale

Answer 2

Hole between RA and LA allowing blood to bypass lungs in a fetus.

Becomes fossa ovalis post birth

Question 3

How much blood does lungs in utero need?

Answer 3

Just enough to allow lung tissue to develop

Question 4

Why is most of the blood going around the fetus body medium O2 content?

Answer 4

Because O2 blood from the placenta is mixed with deoxygenated blood from the babies systemic circuit and is then shunted back into systemic circuit, bypassing the lungs

Question 5

Purpose of shunts?

Answer 5

To bypass lungs (and liver)

Question 6

What happens when the baby is first born to seperate the pulmonary and systemic circuits.

Answer 6

1) infant takes first breath, lungs inflate, pulm. capillaries expand, lungs become lower resistance.

2) Blood leaving RV now has 2 options
- low R into lungs (PREFERRED)
- high R through duc.Art into systemic circulation

3) for 1st time, a large volume enter LA via pulm. veins, LA pressure increases.
4) umbilical vein constricts/clamped. venous return from placenta = 0. Inflow to RA decreases, RA pressure drops
5) LA P> RA P, blood flows from LA to RA, foramen ovale flap closes/seals. Atria seperated.
6) SM in ductus art. contrcts due to higher O2. 10-15 hours it is closed.

Now the Pulm and systemic circuits are physiologically seperate!

Question 7

Heart looping and folding.

Answer 7

Starts off as a primitive tube. (atria upside down to ventricles)
Week 4: Heart tube elongates, curves back on itself and forms an S. Twists and loops back on itself (internally septa form)
Week 5: internal chambers form.

watch video.

Question 8

Why is the formation of the interatrial septum the way it is

Answer 8

To allow more oxygenated blood from the IVC (placenta) to reach the shunt and the de oxygenated (SVC less oxygenated to go on the right side)

Question 9

Draw steps of atrial septal defect.

Answer 9

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Question 10

Draw steps of ventricular septal defect.

Answer 10

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