Embryology Flashcards
Bulbus cordis gives rise to…
Smooth parts (outflow tracts) of left and right ventricles
Primitive atrium gives rise to…
The trabeculated parts of the left and right atria.
Primitive ventricle gives rise to…
The trabeculated part of the left and right ventricles.
The primitive pulmonary vein gives rise to…
The smooth part of the left atrium.
The left horn of the sinus venosus gives rise to…
The coronary sinus.
The right horn of the sinus venosus gives rise to…
The smooth part of the right atrium (sinus venarum).
The right common cardinal vein and right anterior cardinal vein give rise to…
The superior vena cava (SVC).
Heart beats spontaneously by the…week of fetal development.
Fourth
Cardiac looping to establish left-right polarity begins in…
Week 4 of gestation.
Defect in left-right dynein (involved in L/R asymmetry) can lead to…, as seen in…
Dextrocardia; Kartagener syndrome (primary ciliary dyskinesia)
Describe the process by which the atria become septated.
- Septum primum grows toward endocardial cushions, narrowing the foramen primum.
- Foramen secundum forms in septum primum (foramen primum disappears).
- Septum secundum develops as foramen secundum maintains right-to-left shunt.
- Septum secundum expands and covers most of the foramen secundum. The residual foramen is the foramen ovale.
- Remaining portion of septum primum forms valve of foramen ovale.
- Septum secundum and septum primum fuse to form the atrial septum.
- Foramen ovale usually closes soon after birth because of increased left atrium pressure.
Patent foramen ovale is caused by…
Failure of septum primum and septum secundum to fuse after birth. Most are left untreated.
A patent foramen ovale can lead to…
Paradoxical emboli (venous thromboemboli that enter systemic arterial circulation).
Ventricular septal defects most commonly occur in the…
Membranous portion of the septum.
Describe the process by which the ventricles become septated.
- Muscular ventricular septum forms. Opening is called the interventricular foramen.
- Aorticopulmonary septum rotates and fuses with muscular ventricular septum to form the membranous interventricular septum, closing the interventricular foramen.
- Growth of endocardial cushions separates atria from ventricles and contributes to both atrial septation and formation of the membranous portion of the interventricular septum.
Describe the process by which the outflow tracts form.
Truncus arteriosus rotates; neural crest and endocardial cell migrations –> truncal and bulbar ridges that spiral and fuse to form aorticopulmonary septum –> ascending aorta and pulmonary trunk
Conotruncal abnormalities include:
- Transposition of the great vessels
- Tetralogy of Fallot
- Persistent truncus arteriosus
The aortic/pulmonic valves are derived from…
endocardial cushions of the outflow tract.
The mitral/tricuspid valves are derived from…
fused endocardial cushions of the AV canal.
Valvular anomalies may be classified as…
- Stenotic
- Regurgitant
- Atretic (e.g., tricuspid atresia)
- Displaced (e.g., Ebstein anomaly)
Fetal erythropoiesis occurs in:
Yolk sac (3-8 weeks)
Liver (6 weeks to birth)
Spleen (10-28 weeks)
Bone marrow (18 weeks to adult)
Remember: Young Liver Synthesizes Blood
Embryonic globins
Zeta and epsilon
Fetal hemoglobin (HbF) =
Alpha2gamma2
Adult hemoglobin (HbA1) =
Alpha2beta2
HbF has…affinity for O2 due to less avid binding of…, allowing HbF to extract O2 from maternal hemoglobin (HbA1 and HbA2) across the placenta.
Higher; 2,3-BPG
From fetal to adult hemoglobin:
Alpha Always; Gamma Goes, Becomes Beta
Blood in umbilical vein has a PO2 of approximately…and is approximately…saturated with O2.
30 mmHg; 80%
Umbilical arteries exhibit low…
O2 saturation.
Blood entering the fetus through the umbilical vein is conducted via the…into the IVC, bypassing…
Ductus venosus; hepatic circulation
Most of the highly oxygenated blood reaching the heart via the IVC is directed through the…and pumped into the…to supply the head and body
Foramen ovale; aorta
Deoxygenated blood from the SVC passes through the RA, into the RV, into the main pulmonary artery, through the…, into the descending aorta.
Patent ductus arteriosus
Describe the process by which the foramen ovale and ductus arteriosus close following birth.
At birth, infant takes a breath; this decreases resistance in pulmonary vasculature –> increases left atrial pressure vs. right atrial pressure; foramen ovale closes (now called fossa ovalis); likewise, increase in O2 (from respiration) and decrease in prostaglandins (from placental separation) leads to closure of the ductus arteriosus
Prostaglandins E1 and E2…
kEEp PDA open.
…helps close PDA.
Indomethacin
Remnant of ductus arteriosus is known as the…
Ligamentum arteriosum
The urachus is part of the…between the bladder and umbilicus. It becomes the…after birth.
Allantoic duct; median umbilical ligament
The ductus venosus becomes the…
Ligamentum venosum
The notochord becomes the…
Nucleus pulposus.
The umbilical arteries become the…
Medial umbilical ligaments
The umbilical vein becomes the…, which is contained in the…
Ligamentum teres hepatis; falciform ligament
Truncus arteriosus gives rise to…
Ascending aorta and pulmonary trunk
