Embryology of CVS

Question 1

which germ layer is the heart derived from

Answer 1

visceral mesoderm

cranial to the developing neural tube

Question 2

explain the role of embryonic folding in bringing the developing heart into its final position in the thorax

Answer 2

lateral folding

cranio-caudal folding

Question 3

state the names of the different regions of the heart tube and the adult structures each of these regions give rise to

Answer 3

heart tube develops 5 dilatations which then develop into the adult heart structures

truncus ateriosus - aorta and pulmonary trunk
bulbus cordis - trabeculated part of right ventricles, outflow pat of both ventricles
ventricles - trabeculated part of left ventricle
atrium - trabeculated part of both atria
sinus venosus - smooth part of right atrium and coronary sinus

direction of blood flow is caudal to cranial

Question 4

describe the movements that occur during looping and folding of the heart tube

Answer 4

day 23 - heart begins to loop and fold;
atrium - dorsal and cranial
ventricles - displaced left
bulbus cordis - inferiorly, ventrically to the right

Question 5

state the steps in the formation of the septa of the heart

Answer 5

endocardial cushions extend

Question 6

name the 3 venous systems found in the embryo and how they relate to adult venous system

Answer 6

vitelline veins - drains yolk sac;
portal venous system draining gut
hepatic sinusoids and veins
hepatic portion of IVC

umbilical veins - oxygenated blood from placenta;
right degernates - left remains as definitive umbilical vein

cardinal veins - gives systemic venous system;
anterior - drains head and neck (jugular system, left brachiocephalic vein and SVC)
posterior - drains trunk (azygous and hemiazygos systems, gonadal and renal veins, iliac veins and IVC)

Question 7

state the names of the blood vessels that empty into the sinus venosus and how these change as the sinus venosus develops

Answer 7

anterior and posterior cardinal veins via the common cardinal vein
umbilical vein
vitelline vein

merge into horn and then into sinus venosus

then develop into;
right umbilical
left vitelline
left common cardinal

Question 8

describe the venous origins of the smooths parts of the right and left atria

Answer 8

venous origin - sinus venosus