Cardiovacular Embryology- Melissa (3)* Flashcards
By what weeks (gestation) have the endocardial tubes formed?
2-3 weeks (18-19 days)
By what week gestation do the paired endocardial tubes fuse and establish trunks arteriosis outflow?
3 weeks
By when do contractions begin in the fetal heart?
3-4 weeks; 22-23 days
What is happening during week 4 gestation in terms of heart development?
heart tube continues to elongate, curves to form S shape
also circulation begins d27-29
When does atrial and ventricular separation start?
When is it complete?
Week 5/ Day 26
Complete (4 chambers closed) by day 50
At what point does the foramen ovale close?
What rudimentary structure is left?
Week 37/ 38 (after birth in response to the pressure difference)
*Fossa Ovalis remains
Describe the 3 steps that lead up to formation of the single heart tube:
- medial migration of angiogenic cells
- formation of 2 endocardial tubes
- fusion of endocardial tubes (cranial–>caudal) during lateral folding of the embryo
List the 5 dilations of the single heart tube (Cranial–> caudal):
- Truncus arteriosis
- Bulbus cordis
- Primative ventricle
- Primative atrium
- Sinus Venous
Truncus arteriosis derivatives (2):
- proximal aorta
2. proximal pulm. arteries
Bulbs Cordis derivatives (2):
- smooth part of R ventricle (conus arteriosis)
2. Part of left ventricle (smooth also, bc its membranous septum?)
Primitive ventricle derivatives:
Trebeculated portion of rt and lt ventricles
Primitive atrium derivatives:
R (trabeculated), L atria
Sinus venosus derivatives:
- smooth R atrium (R horn)
- coronary sinus (L horn)
- oblique vein
Describe the process of DEXTRAL folding:
What is happening?
Why?
What is the end result?
- Bulboventricular sac grows faster than rest of embryo/ pericardial sac
- Tube folds to the RIGHT–> forms
bulbovenvricualr fold–> organ shifts LEFT - Atrium + sinus venous move dorsal/ cranial and enter pericardial sac
What is the first organ to treat rt/lt symmetry?
Heart!
By when is folding of the heart and migration of neural crest cells to the outflow tract complete?
Day 28 (week 4)
Describe the order of events in atrial septation (6):
- SEPTUM PRIMUM forms
(roof of atrial segment–> endocardial cushion) - SP forms boundaries of FORAMEN PRIMUM
- Apoptosis in posterior SP–> FORAMEN SECUNDUM
- SP closes
- SEPTUM SECUNDUM froms to Rt of SP
(roof of atrial segment–> endocardial cushion) - SS grows in arc anteriorly–> FORAMEN OVALE
What is the foramen ovale/ when is it TECHNICALLY formed?
Foramen ovale is ostium secundum covered by septum secundum. Foramen ovale cannot be called foramen ovale until: septum secundum forms + septum primum joins endocardial cushions.
(Very clear and concise; was trying to describe how s.secundum doesn’t totally close–thank you Leah, for revising :)!)
Describe atrioventricular canal formation (2):
- fusion of superior + inferior endocardial cushions–>
Rt, Lt atrioventricular orifices form - mesenchymal cells form fibrous part of M/T (AV) valves
Describe separation of truncus arteriosis (3):
- neural crest cells elongate outflow tract + aortic arch
- ingrowth of 2 opposing mesenchymal ridges
- spiraling configuration and fusion of ridges (distal–> proximal)
Which three structures fuse to make the membranous portion of the intraventricular septum?
From what heart dilations do they derive?
- Rt bulbar ridge (bulbs cordis)
2, Lt bulbar ridge (bulbs cordis) - AV septum (endocardial cushions)
By what process do the AV valves form?
Delamination of leaflets from superficial myocardium
*Note: myocardium is MESENCHYMAL tissue.
(+ Selective apoptosis to form gaps between leaflets)
How does the muscular portion the ventricular septum form?
How do the 4 chambers all close off?
- apical portions of ventricles balloon out;
- merger of the muscular ventricular septum with the outflow separation closes off the 4 chambers
Derivatives of first aortic arch
Maxillary and external carotid artery (ECA)
Derivatives of second aortic arch
Stapedial and hyoid aa
Derivatives of third aortic arch
Common carotid aa. and proximal internal carotid aa
Derivatives of 4th aortic arch
Lt: aortic arch
Rt: subclavian, then degenerates distally (failure to degenerate = double aortic arch; #1 type of vascular ring!)
Derivatives of 6th aortic arch
proximal: rt, lt pulm. arteries
Left distal: ductus arteriosus
How do the pulm. vv’s form?
By what week have they fused with the developing atrium?
Lung bud 1 + Lung bud 2–>
Primitive pulm vein–>
Incorporates into wall of developing atrium by 8 weeks
By when has common pulm vein differentiated into rt and lt vv’s draining info left side of atrial septum,?
12 weeks
Persistant primitive heart tube:
lethal
Defective looping of heart tube:
dextrocardia, situs inverts
First Aid: Kartagener Syndrome, L –> R dynein deficiency
Effects of double wedging/ ventricular separation:
double outlet right ventricle
Derivatives of dorsal aorta?
Right subclavian
Left subclavian and descending aorta
Derivatives of vittelline arteries
SMA, IMA, Celiac
Derivatives of umbilical arteries:
Internal iliac
Superior vesical
(Arteries)
+ mediaL umbilical ligaments
When and where do coronary arteries originate?
33-39 days
Extracardiac tissue joins aorta in the sinuses of valsalva
What parts of the heart are derived from neural crest cells? What is the rest derived from?
AP septum & carotid body from neural crest cells
The rest is driver from splanchnic mesoderm
What would you expect to see in terms of cardiac development at each of the following times?
- 18-24 days
- 22-24 days
- 26-40 days (2 things)
- 29-55 days
- 33-39 days
- 18-24 days: formation of heart tube
- 22-24 days: heart beats
- 26-40 days (2 things): separation/ chamber formation, great vessel formation
- 29-55 days: valves form
- 33-39 days: coronary vessels form
Memory Hook for Aortic Arches
1: 1st arch is MAXimal (maxillary artery)/ ECA
2: “S” for “s”econd = “s”tapedial/ hyoid
3: C- 3rd letter of alphabet- CCA/ ICA
4th: supplies the FOUR limbs (left- aortic arch, right subclavian)
5th: You won’t “F”ind the “F”ifth anywhere
6: pulmonary arteries/ ductus arteriosus.
(ductus has 6 letters)
Failure of right 4th aortic arch?
Double vascular ring.
