cardiovascular embryology Flashcards
how does heart tube form the atria?
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)
what divides the right and left atria?
septum primum + septum secundum
how is blood shunted from RA to LA in embryo
foramen ovale (of septum secundum) and foramen secundum (of septum primum)
3 possible causes of ASD
foramen secundum gets too big and overlaps foramen ovale
absence of septum secundum
neither septum secundum or septum primum develop
structures that grows to close the opening/canal between atrial chamber and ventricular chamber into two smaller openings
superior endocardial cushion
inferior endocardial cushion
genetic abnormality commonly associated with endocardial cushion defects
trisomy 21
how are the ventricles + outflow tracts separated?
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
cells of truncus arteriosus + aorticopulmonary septum come from
neural crest cells
6 different truncoconical (spiral) septum defects
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
process of remodeling of ventricles in order to form atrioventricular valves
narrow ventricular lumen → myocardium erodes → ventricles enlarge → residual mesodermal fibrous tissue forms chordae tendineae → papillary muscles + AV valves form
truncus arteriosus
great vessels: ascending aorta + pulmonary trunk
bulbus cordis
outflow tract (smooth parts) of LV and RV
primitive atria
muscular part (trabeculated) of LA and RA
primitive ventricle
muscular part (trabeculated) of LV and RV
left horn of sinus venosus
coronary sinus
right horn of sinus venosus
smooth part of RA
what is the adult structure of the ductus arteriosus?
ligamentum arteriosum
what is the adult structure of the ductus venosus?
ligamentum venosum
what is the adult structure of the foramen ovale?
fossa ovalis
what is the adult structure of the umbilical arteries?
medial umbilical ligaments (umbiLical = mediaL)
what is the adult structure of the umbilicial vein?
ligamentum teres (in falciform ligament of liver)
purpose of shunting by ductus venosus
bypass hepatic circulation
umbilical vein → ductus venosus → IVC
purpose of shunting by foramen ovale
blood of IVC (most O2 rich blood) enters foramen ovale → RA to LA → LV → aorta → head + body
purpose of shunting by ductus arteriosus
blood of SVC (deoxy blood) enters RA → RV →main pulmonary artery → ductus arteriosus → descending aorta
changes at birth with fetal circulation
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
drug that closes the PDA if patent
indomethacin (NSAID - inhibit PG synthesis)
drug that keeps ductus arteriosus open
PGE1 or PGE2
right common cardinal vein + right anterior cardinal vein
SVC
primitive pulmonary vein
smooth part of LA
