Embryology Flashcards
1st aortic arch
small part of maxillary
2nd aortic arch
artery to stapedius (small muscle located inside the middle ear)
3rd pair of aortic arches
Common carotid arteries
Right 4th aortic arch
Proximal part of right subclavian artery
Left 4th aortic arch
Arch of aorta
Right 6th aortic arch
Right pulmonary artery
Left 6th aortic arch
Left pulmonary artery and ductus arteriosus
Right 7th segmental arch
Right subclavian artery
Left 7th segmental arch
Left subclavian artery
Right dorsal aorta
Regresses except for a portion that forms middle of the right subclavian artery
Left dorsal aorta
Descending thoracic aorta
Aortic sac
Ascending aorta and brachiocephalic artery
Gastrulation
mass movement and invagination of the blastula to form 3 layer- ectoderm, mesoderm and endoderm
Which cell layer(s) make CVR system
most of cardiovascular system is derived from cells which were situated in the mesoderm (blood, heart, smooth muscle and endothelium)
• Some contribution from cardiac neural crest cells from the ectoderm (contributes to cardiac outflow and coronary arteries)
First heart field
Future left ventricle
Second heart field
outflow tract, future right ventricle and atria
When does development of cardiovascular system begin
Week 3
Stages of embryology of heart - formation of primitive heart tube
- Mesoderm cells travel through primitive streak to embryo’s head and form horseshoe-shaped area with 2 limbs (ie primary heart field)- cardiogenic region
- day 19-21: lateral folding: embryo folds into cylindrical shape as lateral borders meet at midline- 2 endocardial tubes fuse, forming primitive heart tube
- Craniocaudal folding positions in thoracic region
- Heart tube grows and develops bulges
Partition of the heart tube
• sinus venosus: left and right sinus horn bring in blood (superior vena cava) and part of right atrium
• Primitive atrium and primitive ventricle separated by atrioventricular sulcus
• Primitive atrium → left and right atria
• Primitive ventricle → left ventricle
• Bulbus cordis → right ventricle and outflow tracts for both ventricles (aorta and pulmonary trunk)
What happens day 22
Heart begins to beat
Looping of the heart
heart tube folds into C shape
• tube lengthens
• Walls thicken
• Sections move toward appropriate locations to continue development
• Bulbis cordis moves inferiorly, anteriorly and to the embryo’s right
• Primitive ventricle moves to embryo’s left side
• primitive atrium and sinus venosus move superiorly and posteriorly
• Sinus venosus is posterior to primitive atrium
• During development, the node secretes nodal, which circulates to the left due to ciliary movement
• A cascade of transcription factors (e.g. Lefty, Pitx2, Fog-1) transduce looping
How does the Bulbus cordis move
inferiorly, anteriorly and to the embryo’s right
How does the primitive ventricle move
moves to embryo’s left side
Where does the primitive atrium and sinus venosus move to
move superiorly and posteriorly
Sinus venosus is posterior to primitive atrium
Cardiac septation
atrium and ventricle connected by atrioventricular canal
• Blood first enter the atrium passes through the atrioventricular canal and into the ventricle. Exits the heart the the Truncus arteriosus
• Masses of tissue called endocardial cushions grow from the sides of the atrioventricular canal to partition it into 2 separate openings
• As the endocardial cushions grow together, the atrioventricular canal also is repositioned to the right of the heart
• The superior and inferior endocardial cushions fuse, forming 2 separate openings- the left and right atrioventricular canals
• endocardial cells proliferate on ventricular side of each canal- form leaflets of mitral and tricuspid valves
• Canals now divided into atria and ventricles
What does the sinus venosus become
left and right sinus horn bring in blood (superior vena cava) and part of right atrium
What does the primitive atrium become
Left and right atria
What does the primitive ventricle become
Left ventricle
What does the Bulbus cordis become
right ventricle and outflow tracts for both ventricles (aorta and pulmonary trunk)
Formation of blood islands
Day 17 extraembryonic mesoderm. Core of haemoblasts surrounded by endothelial cells
Vasculogenesis
Day 18
angioblasts (from splanchnopleuric mesoderm) coalesce to form angioblastic cords throughout embryonic disc
• Vasculogenesis is added to by angiogenesis- driven by angiogenic growth factors and takes place via proliferation and sprouting
What drives embryonic vessel development
• Angiogenic growth factors – vascular endothelial growth factor, angiopoietin 1 & 2
• Repulsive signals – Plexin / semaphorin signalling, ephrin / Eph interactions
• Attractive signals- VEGF
Fetal Heart shunts
bypassing pulmonary circulation- not require in utero
• Foramen Ovale - between atria
• Ductus Arteriosus - pulmonary artery to aorta
Umbilical vein
Carries oxygenated blood
Umbilical artery
Carries deoxygenated blood
Endocardial cushions
Masses of tissue called endocardial cushions grow from the sides of the atrioventricular canal to partition it into 2 separate openings
• As the endocardial cushions grow together, the atrioventricular canal also is repositioned to the right of the heart
5th aortic arch
Regresses
Extra-embryonic blood vessel formation
Day 17-21
Lateral plate mesoderm -> blood islands -> vasculogenesis
Extra-embryonic blood vessel formation
Day 28
Angiogenesis - proliferation and sprouting -> mesodermal cells recruited for tunica, media and adventitia
Ductus arteriosus becomes…
Ligamentum arteriosum
Foramen ovale becomes …
Fossa oval is
Down and forwards cardiac looping
23 days: bulbus cordis
Up and back cardiac looping
24 days: primitive ventricle
35 days: primitive atrium and sinus venosus
Left right axis determination
Nodes secrete nodal- circulates left due to ciliary movement
What is the embryological derivative of the coronary sinus
Left horn of the sinus venosus
What is the embryological derivative of the smooth part of the right atrium
Right horn of the sinus venosus
What does the first heart field develop into
Left ventricle
What does the second heart field develop into
Right ventricle
Atria
Outflow tracts
Which part of the gastrula forms the CV system
Mesoderm
Describe the process by which the first breath causes a transition from fetal circulation to post-natal circulation
Expands lungs causing pulmonary vasodilation
Reduces pulmonary pressure
Pulmonary shunt closes
Increases left atrial pressure
Foramen ovale closes
A 23 year old man with Marfan’s syndrome is found to have a dilated aortic root. Which embryological structure gives rise to the aortic root?
Truncus arteriosus
