Embryology (Cardio)

Question 1

Truncus arteriosus

Answer 1

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

Question 2

Bulbus cordis

Answer 2

Smooth parts (outflow tract) of left and right ventricles

Question 3

Primitive ventricle

Answer 3

Trabeculated left and right ventricles

Question 4

Primitive atria

Answer 4

Receives blood from sinus venosus in embryo; becomes trabeculated left and right atria

Question 5

Sinus venosus

Answer 5

First receives blood from venae cavae in embryo

Question 6

Left horn of sinus venosus

Answer 6

Becomes coronary sinus

Question 7

Right horn of sinus venosus

Answer 7

Becomes sinus venarum (smooth) in adult right atrium

Question 8

Right common cardinal vein and right anterior cardinal vein

Answer 8

Becomes superior vena cava

Question 9

Truncus arteriosus pathologies

Answer 9

TGA (failure to spiral), tetralogy of Fallot (skewed AP septum development), persistent TA (partial AP septum development)

Question 10

Interventricular septum development

Answer 10

1. ) Muscular ventricular septum forms. Opening=intraventricular foramen
2. ) Rotation of AP septum and fusion with muscular septum –>membranous intraventricular septum and closure of intraventricular foramen
3. ) Growth of endocardial cushions separates atria from ventricles, separates atria from each other

Question 11

Interventricular septum pathologies

Answer 11

TGA (improper neural crest migration), membranous septal defect causes L->R shunt and eventual reversal (Eisenmenger’s)

Question 12

Interatrial septum development

Answer 12

1. ) Foramen primum narrows as septum primum grows towards endocardial cushions
2. ) Perforations in septum primum –> foramen secundum (loss of foramen primum)
3. ) Foramen secundum maintains a R->L shunt as septum secundum grows
4. ) Septum secundum contains a permanent opening (foramen ovale)
5. ) Septum 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 increased LA pressure relative to RA pressure (dec. in pulm vasc resistance)

Question 13

Interatrial septum pathology

Answer 13

Patent foramen ovale (septum primum and septum secundum do not fuse)

Question 14

Fetal erythropoiesis

Answer 14

Yolk sac (3-10 wk)
Liver (6 wk - birth)
Spleen (15-30 wk)
Bone marrow (22 wk-adult)
"Young liver synthesizes blood"

Question 15

Oxygen saturation of fetal vessels

Answer 15

Umbilical vein PaO2: 30 mmHg; 80% sat

Umbilical arteries have low sat

Question 16

Fetal vessel shunts

Answer 16

1. ) Umbilical vein –>IVC via DUCTUS VENOSUS (bypass liver)
2. ) IVC –>aorta via FORAMEN OVALE (bypass ventricles)
3. ) PA –>aorta via DUCTUS ARTERIOSUS (bypass lungs)

Question 17

Patency of ductus arteriosus

Answer 17

Closes with first breath –>O2 leads to decrease in prostaglandins

Prostaglandins keep PDA open, indomethacine helps close PDA

Question 18

Umbilical vein derivative

Answer 18

Ligamentum teres hepatis (falciform ligament)

Question 19

Umbilical arteries

Answer 19

Medial umbilical ligaments

Question 20

Ductus arteriosus

Answer 20

Ligamentum arteriosum

Question 21

Ductus venosus

Answer 21

Ligamentum venosum

Question 22

Foramen ovale

Answer 22

Fossa ovale

Question 23

Allantois

Answer 23

Urachus - median umbilical ligament

Question 24

Notochord

Answer 24

Nucleus pulposus of intervertebral disc