Cardiac looping Flashcards
Very 1st heart structure
Paired endocardial heart tubes
Paired endocardial heart tubes
Splanchnic mesoderm (cardiogenic chords) of lateral plate mesoderm
Folding embryo
lateral folds and fusion cranial to caudal => forms 1 heart tube
Cephalocaudal folding → brings heart into pericardial cavity
3 structural layers of heart tube
Inner endocardial tube = endocardium
Myoepicardial mantle = myocardium + epicardium
Cardiac jelly = myocardium + endocardial cushion tissue
Heart tube chambers
o Truncus arteriosus: bulge cranially to form aortic sac
o Bulbus cordis => will develop as trabeculated RV
o Primitive ventricle
o Sinus venosus: caudal, receive blood from entire embryo
Separated from atrium by sinoatrial sulcus (site of future SA node)
Outside pericardial cavity, fixed by septum transversum
Truncus arteriosus
Ascending Ao + PA
Conus cordis
Smooth OT
Proximal 1/3 of bulbus cordis
RV, trabeculated
Bulboventrocular sulcus
IV foramen => IVS
Primitive ventricle
LV trabeculated
Primitive atrium
rough part of atria
What is looping
bending of heart tube before septation => C shape => S shape
Normal looping
o Asymmetric activity of lateral (↑ active) → rapid growth of bulboventricular portion → saccular shape → greater curvature along R border
Normal looping towards the R
o Cranial aspect of the heart tube bends ventrocaudally and to the R = truncus + bulbus cordis
Heart tube shifts to the L du to cr (Ao roots) and caudal (sinus venosus) attachment
o Caudal aspect of the heart tube bends toward the dorsocranial aspect and towards the left = primitive atria and sinus venosus
Result: Placement of the atrium and sinus venosus above and behind the truncus arteriosus/bulbus cordis/ ventricle
Convergence
Alignement of developing IVS w/ OT portion and AV canal
connection btwn RA and RV + LV to Ao portion of LVOT
AV canal separate primitive atria and ventricles
Wedging
counterclockwise rotation of OT → align LV and AoV
o Wedges between developing MV and TV
Sinus venosus
eventually incorporated in RA => coronary sinus + portion of RA wall
Faulty development of sinus venosus
Sinus venosus defect: dorsocranial to the fossa ovale
* Incomplete embryologic resorption of sinus venosus
* Type of ASD: dorsocranial to the fossa ovale
o Involve portion of atrial wall derived from sinus venosus
Interatrial communication = orifice of the unroofed right pulmonary veins as they pass posterior to the RA
Not true ASD, but hemodynamically similar L to R shunting
o Abnormal attachment of the R PVs to Cr or CaVC
Defect just below the orifice in RA
* CrVC type: more common in Hu
* CaVC type: below foramen ovale
Partial anomalous PV drainage from R lung
Faulty development of common PV
if fails to develop => total/partial anomalous pulmonary venous return
* All 4 PVs connect to the RA as collateral channels
