Embryology

Question 1

Truncus arteriosus gives rise to

Answer 1

Ascending aorta and pulmonary trunk

Question 2

Bulbus cordis gives rise to

Answer 2

Smooth parts (outflow tract) of left and right ventricles

Question 3

Primitive ventricle gives rise to

Answer 3

Trabeculated left and right ventrciles

Question 4

Primitive atria gives rise to

Answer 4

Trabeculated left and right atria

Question 5

Left horn of sinus venosus gives rise to

Answer 5

Coronary sinus

Question 6

Right horn of sinus venosus gives rise to

Answer 6

Smooth part of right atrium

Question 7

Right common cardinal vein and right anterior cardinal vein gives rise to

Answer 7

Superior vena cava

Question 8

How is truncus arteriosus formed

Answer 8

Neural crest migration –> truncal and bulbar ridges that spiral and fuse to form the aorticopulmonary (AP) septum –> ascending aorta and pulmonary trunk

Question 9

Pathology of truncus arteriosus failure to spiral

Answer 9

Transposition of great vessels (or due to improper neural crest migration into the TA)

Question 10

Pathology of truncus arteriosus skewed AP septum development

Answer 10

Tetralogy of Fallot

Question 11

Pathology of truncus arteriosus partial AP septum development

Answer 11

Persistent TA (or due to improper neural crest migration into the TA_

Question 12

Three steps of interventricular septum development

Answer 12

1. muscular ventricular septum forms with the opening called interventricular foramen
2. AP (aoritcopulmonary) septum rotates and fuses with muscular ventricular septum to form membranous interventricular septum - closing interventricular foramen
3. Growth of endocardial cushions separates atria from ventricles and contributes to both atrial separation and membranous portion of the interventricular septum

Question 13

Eisenmenger’s syndrome

Answer 13

Membranous septal defect causes an initial left-to-right shunt which later reverses to a right-to-left shunt due to the onset of pulmonary hypertension

Question 14

Interarterial septum development eight steps

Answer 14

1. Foramen primum narrows as septum primum grows toward endocardial cushions
2. Perforations in septum primum form foramen secundum (foramen primum disappears)
3. Foramen secundum maintains right-to-left shunt as septum secundum beings to grow
4. Septum secundum contains a permanent opening (foramen ovale)
5. Foramen secundum enlarges and upper part of septum primum degenerates
6. Remaining portion of septum primum forms valve of foramen ovale
7. Septum secundum and septum primum fuse to form the atrial septum
8. Foramen ovale usually closes soon after birth because of increase left atrial pressure

Question 15

Patent foramen ovale

Answer 15

Caused by failure of septum primum and septum secundum to fuse after birth

Question 16

Fetal erythropoiesis sites at:
3-10 week
6 week to birth
15 to 30 week
22 week to adult

Answer 16

Yolk sac - 3 to 10 week
Liver - 6 week to birth
Spleen - 15 to 30 week
Bone marrow - 22 week to adult 
Young Liver Synthesizes Blood  - fetal Hb of alpha 2 and gamma 2, adult Hb of alpha 2 and beta 2

Question 17

Fetal Circulation pathway

Answer 17

Blood (oxygenated from placenta) enters fetus though umbilical vein through ductus venosus into IVC (bypass hepatic circulation) –> heart –> foramen ovale –> out the aorta –> head and body
Deoxygenated blood entering RA from SVC –> RV –> pulmonary artery –> ductus arteriosus –> descending aorta –> umbilical arteries –> placenta

Question 18

When infant takes first breath what happens?

Answer 18

Decreased resistance in pulmonary vasculature causes increase LA pressure vs. right atrial pressure –> foramen ovale closes (fossa ovalis) –> increase in O2 leads to decrease in PG –> closure of ductus arteriosus

Question 19

What drug is used to close PDA?

Answer 19

Indomethacin

Question 20

What can keep PDA open?

Answer 20

Prostaglandins (PG) E1 and E2

Question 21

Umbilical vein postnatally turns into

Answer 21

Ligamentum teres hepatis - in the falciform ligament

Question 22

Umbilical arteries postnatally turn into

Answer 22

Medial umbilical ligaments

Question 23

Ductus arteriosus postnatally turns into

Answer 23

Ligamentum arteriosum

Question 24

Ductus venosus postnatally turns into

Answer 24

Ligamentum venosum

Question 25

Foramen ovale postnatally turns into

Answer 25

Fossa ovalis

Question 26

Allantois postnatally turns into

Answer 26

Urachus-median umbilical ligament (part of the allantoic duct between the bladder and the umbilicus) –> Urachal cyst or sinus is a remnant

Question 27

Notochord postnatally turns into

Answer 27

Nucleus pulposus of intervertebral disc