Fetal Circulation Flashcards
Primitive heart tube receives blood from what 3 venous sources?
- Vitelline veins
- umbilical vesicle/yolk sac to heart - Cardinal veins
- body to heart - Umbilical veins
- chorionic sac/placenta to heart
During 4th week of development, where does oxygenated blood exit the heart?
via aortic sacs and the pharyngeal (aortic) arch arteries that supply the pharyngeal arches and flows to the dorsal aorta
what does the dorsal aorta become?
-fuse caudally to become the common aorta which delivers blood to the rest of the body
When do pharyngeal arch arteries develop?
4th week
What do pharyngeal arch artery derivatives form?
form the fetal arterial system by 8th week
How many pairs of pharyngeal arch arteries form?
- 6 pairs develop
- by the time the 6th pair forms, the first 2 have disappeared
1st PAA derivative?
- mostly disappears
- contribution to Maxillary Artery
2nd PAA derivative?
- disappears mostly
- contribution to Hyoid and Stapedial arteries
3rd PAA?
- ventral part to Common Carotid
- dorsal part to Internal Carotid
4th PAA?
- right side: proximal part of Subclavian artery
- left side: part of Aortic arch
5th PAA?
rudimentary vessel
6th PAA?
- right side: part of right pulmonary artery
- left side: part of left pulmonary artery and ductus arteriosus
Change of course of Recurrent Laryngeal Nerve?
- Asymmetric transformation of 6th PAA cause recurrent laryngeal to change
- Right degenerates distally, moves to hook around proximal right Subclavian artery
- Left hooks around ductus arteriosus which involutes to become ligamentum arteriosum after birth
Coronary vessel formation?
- Proepicardium provides cell precursors for coronary vessels
- Proepicardial cells migrate out to form epicardium
- Epicardium undergoes EMT to form vascular smooth muscle cells and endothelial cells of coronary vessels
- Newly formed coronary arteries enter the Aorta
Vitelline Veins development?
- drain yolk sac and enter sinus venous
- anastomose around duodenum to form portal vein
- hepatic sinusoids incorporate into liver
- Left vitelline regresses
- Right vitelline form hepatic portal system (superior mesenteric) and part of IVC
Umbilical veins development?
- paired umbilical veins transport oxygenated blood from placenta to sinus venosus
- right umbilical regresses
- left umbilical forms shunt through liver to t he IVC, the ductus venosus
Anterior Cardinal veins development?
- Anastomosis between left and right allows shunting of blood
- anastomotic shunt becomes left brachiocephalic vein upon losing connection with left common cardinal
- right anterior cardinal becomes right brachiocephalic vein
Posterior Cardinal veins development?
- Subcardinals
- anastomose between kidneys, forms IVC (renal), renal veins, and gonadal veins - Supracardinals
- anastomose across midline
- forms azygous and hemiazygous vein and superior intercostal veins - Sacrocardinals
- anastomose between subcardinals and supracardinals
- form IVC (lumbar) and common iliac veins
Common cardinal veins development?
- joins anterior and posterior cardinals
- enters sinus venosus
- left common cardinal forms oblique vein of left atrium
- right common cardinal forms SVC
How does oxygenated blood reach the fetus?
-form placenta to fetus via Umbilical Vein
Ductus venosus?
-blood shunt that bypasses liver and enters IVC
Foramen Ovale?
- blood shunt that bypasses the right ventricle
- goes straight from right to left atrium
- bypasses pulmonary circulation
Ductus Arteriosus?
- some blood passes through tricuspid valve into right ventricle
- pumped through pulmonary artery
- blood shunt that bypasses lungs, reaches descending Aorta
How does deoxygenated blood return back to the mother?
-from fetus to placenta via Umbilical arteries
What is the first thing that happens with the first breath?
Ductus venosus constricts into the ligamentum venosum
What does the first aeration of the lungs cause?
- decreased pulmonary vascular resistance
- increased pulmonary blood flow
- thinning of pulmonary arterial walls
- increased left atrial pressure to close the foramen ovale
- increase pO2 through ductus arteriosus
- increased Bradykinin secretion
- decreased prostaglandin E2 and Prostacyclin I2 production
- Ductus Arteriosus constricts into the ligamentum arteriosum
- left ventricle hypertrophies
Ventricular septal defect?
- most common type of congenital heart defect
- membranous VSDs are the most common and result from failure of IV muscular and membranous ridges to align properly with bulbar ridges and AV cushions
Atrial septal defects? 4 clinically significant?
- most common is patent foramen ovale
- clinically insignificant unless accompanied by other defects
- 4 types clinically significant ASDs:
1. ostium secundum
2. ostium primum with endocardial cushion defect
3. sinus venosus defect
4. common atrium
Transposition great arteries?
- most common cause of cyanotic heart disease in newborns
- Aorta lies anterior and to right of pulmonary trunk, arises from morphologic right ventricle
- Pulmonary artery arises from morphologic left ventricle
- associated with other anomalies (ASD, VSD) that permit shunt of blood between systemic and pulmonic circulations
Chest xray of transposition of great arteries?
- egg on a string appearance with increased pulmonary vascularity
- occurs more often in males
Persistent truncus arteriosus?
- results from failed septation of truncus into an aortic and pulmonary trunk
- single arterial trunk arises from heart to supply pulmonic, systemic and coronary circulation
- cyanotic congenital defect that is always accompanied by VSD the allows for circulatory flow circuit completion
