The following table or figure may be downloaded to PowerPoint for personal use in teaching and presentations. This feature is available to all subscribers to the journal.
You MUST read and follow the guidelines at Request to Reproduce AJR Content if you are distributing or using AJR content beyond academic use (limited distribution, non-revenue producing, or educational purposes).
(Downloading may take up to 30 seconds.
If the slide opens in your browser, select File -> Save As to save it.)
Click on image to view larger version.
Fig.4. —Proposed embryogenesis of four passages draining venous blood
from left upper body to heart.
A, Four-millimeter embryo: Left anterior and posterior cardinal
veins join to form left common cardinal vein (black), entering left
sinus horn and then primitive sinus venosus, eventually becoming coronary
sinus.
B, Ten-millimeter embryo: Development of intersubcardinal
anastomosis is illustrated. Analogously, we postulate formation of
intersupracardinal anastomosis (gray) around this period. This
anastomosis should have vertical connections oriented along cephalocaudal axis
and different ventral-dorsal planes. Large defect in illustrated
intersupracardinal anastomosis leaves space for development of primitive
aortopulmonary system (not shown).
C, Seventeen-millimeter embryos: These diagrams show regression of
different parts of previous intersupracardinal anastomosis as result of
failure to successfully compete for available space taken by growth of
truncoaortic sac and primitive aortic arch system (not shown).
D, Twenty-four-millimeter embryos: Primitive models of major venous
channels between bilateral cardinal veins are illustrated. Vessel shown in D1
will become left brachiocephalic vein. Figure reveals nearly total regression
of middle and distal portions of left common cardinal vein to become fibrous
ligament. Vessel in D2 will become anomalous brachiocephalic vein. Greater
preservation of distal portion of left common cardinal vein is constituted as
forming proximal part of this vessel. Middle portion of left common cardinal
vein is totally obliterated and becomes a fibrous ligament. This ligament is
shorter in D2 than in D1. Total preservation of left common cardinal vein
results in a persistent left superior vena cava with either presence (D3) or
absence (D4) of normal left brachiocephalic vein.
