Fetal Cardio Flashcards
When does formation of the embryonic vessels and heart begin?
day 18
What are sites of hematopoiesis?
Yolk sac>Intraembryonic organs>liver>spleen>thymus>bone marrow
How does blood formation occur?
Mesenchymal cells differentiate into angioblasts, which aggregate to form blood islands which contain pluripotent hematopoietic stem cells. During vasculogenesis, cavities appear and angioblasts form an endothelial cell lining. Cavities fuse to form a network of endothelial channels during angiogenesis.
How do endocardial tubes form?
bilateral, parallel endocardial tubes form by vasculogenesis in the rostral splanchnic mesoderm, This embryonic folding occurs cranial to caudal during 3rd-4th weeks
What does sinus venarum become?
becomes sinus venarum, coronary sinus, oblique vein left atrium
What does primitive atrium become?
trabeculated parts of atria
What does primitive ventricle become?
trabeculated parts of left ventricles
What does bulbus cordis become?
conus arteriosus (smooth part of right ventricle), aortic vestibule (smooth part of left ventricle
What does truncus arteriosus become?
ascending aorta
pulmonary trunk
How does heart loop during the 4th week?
The cardiac loop forms when the cranial aspect of the heart tube bends ventrocaudally and to the right while the caudal aspect of the heart tube bends toward the dorsocranial aspect and towards the left. The formation of the cardiac loop takes approximately five days and usually complete by day 28
What happens in dextrocardia?
If a D-bulboventricular loop fails to migrate into the left hemithorax, it can result in dextrocardia with the heart in the right hemithorax.
What do cells of secondary heart field form?
derivatives at arterial pole, parts of right ventricle and OFT
What do do extracardiac progenitor cells give rise to?
cardiac neural crest cells and proepicardium
When and how does cardiac septa form?
during 4th-6th weeks the formation of AV cushions allow septation of AV canal and OFT, the myocardium deposits inducing epithelial mesenchymal transformation of endocardium at AV border
What forms membranous portion of atrial/ventricular septa, AV canal, and valves?
when neural crest cells invade conotruncal region to form aortic/pulmonary OFT branches
When does atrial septation form?
the 5th week and finishes after birth when foramen ovale
grows as a crescent-shaped wedge from dorsal wall toward cushions forming in AV canal
septum primum
allows oxygenated blood to be shunted from right to left atria like foramen secundum, Dorsal and ventral AV cushions form to divide canal and becomes obliterated
foramen primum
grows from dorsal wall of right atrium to the right of septum primum
septum secundum
continues to grow cranial-caudally and ventral-dorsally; stops before AV septum to form foramen ovale
septum secundum
remains open until gestation
foramen ovale
How does heart remodel itself?
does cardiac looping and chamber expansion to properly align left and right AV canals with correct atrium and ventricle. Then the Atrioventricular septum forms during 5th-6th weeks
Outflow tract (OFT) repositions to override AV canal and provide direct path from LV to OFT
How does septation of ventricle occur?
muscular IV septum grows toward AV cushion and fuses with AV cushion and conotruncal ridges to form membranous IV septum
How is aorticopulmonary septum made?
by conotruncal ridges that divide the OFT into aortic and pulmonary. The septum is formed by neural crest derived cushion cells in the conotruncal ridges
How is OFT septated?
cushion cells pair with conotruncal ridges that divide OFT. These conotruncal ridges spiral down OFT to for aorticopulmonary septum, and connect the RV with pulmonary and LV with systemic.
Fusion of what 3 things equals membranous septum?
conotruncal ridges, muscular IV septum, ventricular AV septum
What is importance of endocardial derived neural crest?
The cardiac neural crest make pharyngeal arches in conotruncal ridges and these ridges make aorticopulmonary septum. Without this you get single outflow
What contributes to the formation of semilunar valves?
tubercles and neural crest cells
What is arterial outflow path?
aortic sac>aortic arch arteries, which arise 4th-5th wk and form arterial system 8th wk> dorsal aorta> vitelline, umbilical, coronary arteries
What is venous inflow path?
vitelline veins> cardinal veins> umbilical veins
What do each of the aortic arches develop into?
What causes the recurrent laryngeal branch to change course in wk 8?
Asymmetric development of left and right 6th pharyngeal arches and displacement by larynx causes recurrent laryngeal nerve (RLN) to change its course. Right RLN - degenerates distally; loops under the right subclavian artery Left RLN - loops under ductus arterious which becomes ligamentum arteriosum
paired vessels supplying the yolk sac
forms vessels supplying derivatives of foregut, midgut, hindgut
vitelline arteries
paired branches of dorsal aorta that go to placenta
persist after birth as internal iliac and superior vesical arteries
umbilical arteries
How do coronary arteries form?
proepicardium forms epicardium, epicardium becomes coronary vascular muscle. Goes through vasculogenesis and angiogenesis to make coronary vessels that invade aorta
What is fate of vitelline veins?
drain yolk sac and enter sinus venosus to: make hepatic sinusoids, form hepatocardiac inferior vena cava, duodenal anastomosis (portal vein), and mesenteric vein. Left vitelline regresses
What is fate of umbilical veins?
They transport oxygenated blood from placenta to sinus venosus and the proximal veins regress, while distally they disappear, the distal left and right hepatocardiac channel form ductus venosus to bypass liver.
After birth what do left UV and ductus venosus form?
ligamentum teres hepatis and ligamentum venosum
Anterior: drain cephalic region
Posterior: drain rest of body
Common: connect anterior and posterior to enter sinus venosus
cardinal veins which forn anastomosis to shunt blood becoming left brachiocephalic vein after losing connection with left common CV, and the right CV becomes brachiocephalic then internal/external jugular
What replace posterior cardinal veins?
Subcardinals: drain kidneys
Supracardinals: drain body wall via intercostal veins
Sacrocardinals: drain lower extremities
Common cardinal vein fates:
Joins the anterior and posterior cardinals
Enters sinus venosus, Forms oblique vein of left atrium, SVC segment, coronary sinus
Anatomic shunts in fetus:
Ductus venosus – most blood bypasses liver
Foramen ovale – most blood bypasses right ventricle via R to L shunt across atria Ductus arteriosus – connects aorta & pulmonary artery to bypass lungs
What happens after birth?
Placental blood flow stops, Ductus venosus becomes ligamentum venosum, Aeration of lungs causes: decreases pulmonary vascular resistance, increase pulmonary blood flow, and thinning of pulmonary arterial walls, increase pO2 through ductus arteriosus, Ductus arteriosus becomes ligamentum arteriosum, and Left ventricle hypertrophies
what closes formaen ovale?
when left atrial pressure greater than right
why shouldn’t pregnant women take NSAIDs?
it can decrease levels pf PGE 2 and prostacyclin 12 which can cause ductus arteriosus to prematurely become ligamentum arteriosum
Ventricular septal defects
most common; result from failed fusion of muscular IV septum with conotruncal ridges and ventricular side of AV septum; cause abnormal shunting of blood from left-to-right side of heart and pulmonary hypertension
atrial septal defects
4 types: ostium secundum, ostium primum with endocardial cushion defect, sinus venosus defect,
common atrium
Patent Ductus Arteriosus
failure of closure of ductus arteriosus leads to frequent abnormality of the great vessels
commonly observed in premature infants,
permits blood to shunt between aorta and pulmonary artery
tranposition of great arteries
causes cyanotic baby because Aorta lies anterior and to right of pulmonary trunk; arises from morphologic RV due to failed spiraling. This permit shunting of oxygenated blood between systemic and pulmonic circulations (mixing blood); fixed by Arterial switch operation corrects dextro-position of great arteries and transplants the coronary arteries
persistent truncus arteriosus
single outflow vessel from heart to supply pulmonary, systemic and coronary artery circulations
caused by failure of neural crest cells to migrate to conotruncal and form aorticopulmonary septum whihc divides aortic and pulmonary
