cardiovascular embryology

Question 1

how does heart tube form the atria?

Answer 1

tube elongates and folds into S shape → atrial chamber lays posteriorly in S, ventricular chamber lays anteriorly in S
atrial chamber grows and becomes SVC and pulmonary vein
septum primum grows toward endocardial cushions (foramen primum forms holes superiorly to allow blood flow from R→L; holes coalesce (apoptosis) in septum primum to form foramen secundum)
septum secundum grows toward endocardial cushions (foramen ovale forms inferiorly, covers foramen secundum)

Question 2

what divides the right and left atria?

Answer 2

septum primum + septum secundum

Question 3

how is blood shunted from RA to LA in embryo

Answer 3

foramen ovale (of septum secundum) and foramen secundum (of septum primum)

Question 4

3 possible causes of ASD

Answer 4

foramen secundum gets too big and overlaps foramen ovale
absence of septum secundum
neither septum secundum or septum primum develop

Question 5

structures that grows to close the opening/canal between atrial chamber and ventricular chamber into two smaller openings

Answer 5

superior endocardial cushion

inferior endocardial cushion

Question 6

genetic abnormality commonly associated with endocardial cushion defects

Answer 6

trisomy 21

Question 7

how are the ventricles + outflow tracts separated?

Answer 7

ventricular chamber lays anteriorly in S-shaped heart tube→ muscular ventricular septum grows upward toward endocardial cushion → divides ventricles
truncoconical swellings (ridges) of truncus arteriosus grow toward eachother + fuse in middle + turn 180° → form spiral septum (aorticopulmonary septum) → divides truncus arteriosus into ascending aorta + pulmonary trunk
inferior portion of spiral septum meets with muscular ventricular septum → form membranous interventricular septum → divide the ventricles and form the aorta and pulmonary arteries

Question 8

cells of truncus arteriosus + aorticopulmonary septum come from

Answer 8

neural crest cells

Question 9

6 different truncoconical (spiral) septum defects

Answer 9

tetrology of fallot
persistent truncus arteriosus: partial spiral septal development
transposition of great vessels (RV → aorta, LV →PA) - no 180° turn of aorticopulmonary septum
less likely to need to know:
dextrocardia
VSD
fenestrae

Question 10

process of remodeling of ventricles in order to form atrioventricular valves

Answer 10

narrow ventricular lumen → myocardium erodes → ventricles enlarge → residual mesodermal fibrous tissue forms chordae tendineae → papillary muscles + AV valves form

Question 11

truncus arteriosus

Answer 11

great vessels: ascending aorta + pulmonary trunk

Question 12

bulbus cordis

Answer 12

outflow tract (smooth parts) of LV and RV

Question 13

primitive atria

Answer 13

muscular part (trabeculated) of LA and RA

Question 14

primitive ventricle

Answer 14

muscular part (trabeculated) of LV and RV

Question 15

left horn of sinus venosus

Answer 15

coronary sinus

Question 16

right horn of sinus venosus

Answer 16

smooth part of RA

Question 17

what is the adult structure of the ductus arteriosus?

Answer 17

ligamentum arteriosum

Question 18

what is the adult structure of the ductus venosus?

Answer 18

ligamentum venosum

Question 19

what is the adult structure of the foramen ovale?

Answer 19

fossa ovalis

Question 20

what is the adult structure of the umbilical arteries?

Answer 20

medial umbilical ligaments (umbiLical = mediaL)

Question 21

what is the adult structure of the umbilicial vein?

Answer 21

ligamentum teres (in falciform ligament of liver)

Question 22

purpose of shunting by ductus venosus

Answer 22

bypass hepatic circulation

umbilical vein → ductus venosus → IVC

Question 23

purpose of shunting by foramen ovale

Answer 23

blood of IVC (most O2 rich blood) enters foramen ovale → RA to LA → LV → aorta → head + body

Question 24

purpose of shunting by ductus arteriosus

Answer 24

blood of SVC (deoxy blood) enters RA → RV →main pulmonary artery → ductus arteriosus → descending aorta

Question 25

changes at birth with fetal circulation

Answer 25

breath in → ↓ intrathoracic pressure → ↓ resistance in pulmonary vasculature (lower pressure than DA pathway)→ more blood enters pulmonary artery → more blood through LA →↑ LA pressure → septum primum pushes against septum secundum → close foramen ovale (now fossa ovalis)
↑ O2 in blood from LA to LV to aorta → ↓ PG synthesis →closes ductus arteriosus within 24 hrs (usually) to 2 wks

Question 26

drug that closes the PDA if patent

Answer 26

indomethacin (NSAID - inhibit PG synthesis)

Question 27

drug that keeps ductus arteriosus open

Answer 27

PGE1 or PGE2

Question 28

right common cardinal vein + right anterior cardinal vein

Answer 28

SVC

Question 29

primitive pulmonary vein

Answer 29

smooth part of LA