Embryology Flashcards
What forms the circulatory system
The lateral plate splanchnic mesoderm
What do angiogenic cell islands form
Two primitive heart tubes
First major system to function in an embryo
Cardiovascular as nutrition by diffusion is no longer sufficient
Where do blood vessels first appear
Yolk sac, allantois, connecting stalk and chorion
Angioblastic cords
Paired endothelial strands that appear in the cardiogenic mesoderm. Canalize to form heart tubes which then join to blood vessels to form primordial cardiovascular system
What folding forms the pericardium
Cranial folding of the embryo
What are the parietal and fibrous pericardium formed from
Somatic lateral mesoderm
What forms the visceral pericardium
Splanchnic mesoderm
Parts of primitive heart tube
Truncus arteriosus Bulbus cordis ventricle Atrium Right and left horns of sinus venosus
Where does the sinus venosus get blood from 3 places
Yolk sac(vitelline) and placenta(umbilical) and body of embryo(common cardinal vein)
fate of Truncus arteriosus
Continues cranially(towards head) with the aortic sac, which the aortic arches arise from and then terminate in the dorsal aorta
Formation of cardiac (bulboventricular) loop
The bulbus cordis and ventricle grow faster so a U shaped bulboventricular loop is formed
Dextrocardia
Backwards heart(heart tube loops to the left) most common positional abnormality of the heart
What does the endocardial cushion separate
atriums from ventricles but leaves left and right AV canals
What does the septum separate
right from left
Separation of atriums
Septum primum forms foramen primum then septum primum splits off on right and foramen secondum forms (in septum primum)
Septum secondum grows next to both and septum primum degenerates, foramen ovale is formed (closes on birth)
Role of foramen ovale
Allows blood to pass from right to left atrium as lungs are non functional
Oval fossa
Remnant of foramen ovale
Oval fossa
Remnant of foramen ovale
How does foramen ovale close
Septums fuse
Atrial septal defect
Open foramen ovale (hole in heart)
A) foramen secondum defect
B) endocardial cushion defect
C) sinus venosus defect
D) common atrium
Partitioning of the ventricles
A muscular septum forms (intraventricular septum forms)
Aorticopulmonary septum (between bulbis cordis and truncus arteriosus) fuses with it to form a membranous septum
Endocardial cushions help
Partitioning of bulbus cordis and truncus arteriosus
During 5th week, by aorticopulmonary septum into aorta and pulmonary trunk in a spiral
Ventricular septal defects
Most common types of CHD
Some can close spontaneously
Conducting system of the heart formation- what week and where are some from
SA node develops in 5th week
AV node and bundle of His develop from AV canal cells and sinus venosus
Cause of SIDS
sudden infant death syndrome
Abnormalities of conducting system in heart
Causes of congenital heart disease
Rubella infection in pregnancy (PDA)
Maternal alcohol abuse (septal defects)
Maternal drug treatment and radiation
Genetics
Transposition of great heart vessels
Cause cyanotic disease in newborns
Permit exchange of systemic and pulmonary circulation
Aorticopulmonary septum may not be a spiral
Or neural crest cells may not migrate properly
4 defects in tetralogy of Fallot
Pulmonary stenosis (blood can’t get out of right ventricle)
Ventricular septal defect
Dextraposition of aorta
Right ventricular hypertrophy
Cause of tetralogy of Fallot
Unequal division of the conus due to anterior misplacement of aorticopulmonary septum
Two methods of blood vessel development
Vasculogenesis (new) and angiogenesis (growth)
Vasculogenesis
New formation of a primitive vascular network
Angiogenesis
Growth of new vessels from pre-existing blood vessels
what is the aortic sac and where do they come from
An extension of the truncus arteriosus, the two primitive aortas ventral parts fuse and aortic branches arise
Future neck
Pharyngeal arches
Pharyngeal arteries
Communicate with aortic branches and aortic arches are formed, 6 on each side with dorsal aortae
Fate of arches 1 and 2
Disappear early and remnant of first forms maxillary artery
Fate of arch 3
Internal carotid artery
Fate of arch 4
Right subclavian
And (left) distal part of aortic arch
Fate of arch 5
Either never forms or regresses
Fate of arch 6
Proximal part of right forms right pulmonary artery
Left forms left pulmonary artery and ductus arteriosus which turns into ligamentum arteriosum
Aberrant subclavian artery
The right subclavian artery is on the left side because right dorsal aorta and aortic arch have regressed.
It crosses behind the trachea and oesophagus
Double aortic arch
Non regression of the right aortic arch forming a vascular ring around the trachea and oesophagus, usually causing difficulty breathing and swallowing
Patent ductus arteriosus
Associated with maternal rubella infection
Ligamentum arteriosum isn’t formed so aortic blood goes into pulmonary artery
Causes ARDS, work of breathing and poor weight gain
Coarctation of the aorta
Aorta is narrow usually due to ductus arteriosus pulling it when ligamentum arteriosum forms
Body veins in embryo
Anterior and posterior cardinal
Fate of vitelline arteries
Supply yolk sac then are arteries in foregut, midgut and hindgut
Fate of vitelline arteries
Supply yolk sac then are arteries in foregut, midgut and hindgut
Fate of umbilical arteries
In embryo are paired branch as of the dorsal aorta
Then internal iliac and superior vesical branches to bladder
Fate of cardinal veins
Form Vena Cava by anastomosis by veins
Double inferior Vena cava- what level and persistence of what vein
At lumbar level from persistence of left sacrocardinal vein
Absent inferior Vena cava
Lower half of the body is drained by azygous vein. Hepatic vein enters heart at site if inferior Vena Cava
Development of lymphatic system
End of sixth week, around veins. Will join lymph sacs later
Order of foetal circulation before birth
Aorta to descending aorta to abdominal aorta to common iliac artery to umbilical arteries to umbilical vein
Ductus venosus
Shunts left umbilical vein to inferior Vena Cava to allow oxygenated blood from placenta to bypass liver
Ductus arteriosus
Allows blood that gets into right ventricle to bypass the lungs
Neonatal circulation changes after birth
Ductus venosus becomes ligamentum venosum
Ductus arteriosus becomes ligamentum arteriosum
Oval foramen becomes fossa ovalis
Umbilical arteries become medial umbilical ligaments
