DeWitt Echocardiography CH 2: Basic Embryology &
Fetal Circulation Questions with Correct Answers
Week 3 Correct Answer-prior: heart consists of pair of tubes on either
side of midline; 2 distinct layer of cells; inner, thinner layer forms
endocardium and outer, thicker layer forms myocardium; 21-23 days:
heart tubes --> midline folding process --> single endocardial heart tube
that connects with AO arch system --> cephalic end and sinus venosus at
caudal end
Sinus Venosus (week 3) Correct Answer-formed by union of 3 veins:
common or cardinal, vitelline, and umbilical; ultimately forms the SVC,
IVC, pulmonary veins, coronary sinus, oblique vein of LV, and posterior
portions of RA and LA
Primitive Atrium (week 3) Correct Answer-will divide into RA and LA
upon development of IAS
Atrioventricular Sulcus (week 3) Correct Answer-Divides the primitive
atrium and primitive ventricle
Primitive Ventricle (week 3) Correct Answer-originates superior to
primitive atrium; finds proper position inferior to primitive atrium;
ultimately forms apical portion of LV; will contribute to the inlet portion
of RV
Interventricular Sulcus (week 3) Correct Answer-Divides the primitive
ventricle and bulbus cordis
, Bulbus Cordis (week 3) Correct Answer-3 parts: proximal portion =
forms apical portion of RV, mid portion "conus cordis" = forms RVOT
and LVOT, distal portion "truncus arteriosus" = forms aorta and main
pulmonary artery
Aortic Sac (week 3) Correct Answer-forms 5 pairs of aortic arches; left
4th arch = definitive AO arch, distal left 6th arch = ductus arteriosus;
additional arches form proximal portions of = right and left PA,
innominate artery, right subclavian artery, and common carotid arteries;
some AO arches are obliterated/disappear by birth
Week 4 Correct Answer-bilateral heart tubes completely fused into
single tube; muscular contractions occur and HEART BEGINS TO
BEAT; initially HR is 60-70 bpm but by birth is ~130-150 bpm
Bulboventricular Loop (week 4) Correct Answer-heart grows rapidly
forcing tube to fold in on itself forming S-shaped loop. Normally folds
to right "d-looping" and finds correct anatomical position
Septum Primum (week 4) Correct Answer-apprears from the dorsal wall
of primitive atrium and grows toward the endocardial cushions
*"ostium primum" remains
Sinoatrial Orifice (week 4) Correct Answer-sinus venosus and primitive
atrium communicate via this; centrally located; over time, shifts to right
side of primitive atrium so that it communicates solely with the RA
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