CVS 3 Embryology Flashcards
What are the relative pressures in the atria in utero?
- Right atrial pressure > left atrial pressure
- Oxygenated blood from the placenta arrives to the RA via the umbilical vein draining into the IVC
What germ layer does the heart and vessels arise from?
Mesoderm
How does folding of the embryo in the 4th week change the position of the caridogenic field?
Moves it caudal to the oropharyngeal membrane
What are the parts of the heart from cranial to caudal?
What do they give rise to?
- Truncus arteriosus: pulmonary trunk + aortic arch
- Bulbous cordis: RV + R+L outflow tracts
- Primitive ventricle: LV
- Primitive atrium: RA+LA
- Sinus venosus:
Describe the inflow and outflow of the initial developing heart
Inflow at caudal end
Outflow at cranial end
When is the midline heart tube formed?
3 weeks
What layer of the pericardium touches the heart?
Visceral layer
What is the transverse sinus?
Gap between arteries and veins
What is the oblique sinus?
Space within pericardial cavity behind heart
What is the adult atrium formed from?
Rough part - primitive atrium
Smooth part - Sinus venosus
Where does the SAN form from?
Sinus venosus
What forms from the 4th aortic arch?
Left - aortic arch
Right - right subclavian artery
What forms from the 3rd aortic arches?
Right - Carotid arteries
What forms from the 6th aortic arch?
Left - pulmonary artery + ductus arteriosus
Right - pulmonary artery
Why is there not a 5th aortic arch?
5th aortic arch degenerates
What happens to the 6th aortic arch on the right side?
Not needed so degenerates + disappears
What are the fetal shunts?
Ductus venosus - by passes the liver
Ductus arteriosus - bypasses the lungs
Foramen ovale - RA > LA
What happens to ductus venosus after birth?
Becomes ligamentum venosum
What happens to ductus arteriosus after birth?
Ligamentum arteriosus
What happens to foramen ovale after birth?
Fossa ovalis
What are the septums involved in splitting the heart into 4 chambers?
- Outflow septum > splits into aorta + pulmonary trunk
- Interventricular septum > R+L ventricle
- Atrioventricular septum > forms V valves
- Interatrial septum > R+L atrium
What forms the AV valves?
Endocardial cushions meeting to form tricuspid + mitral valve
Outline the process of atrial septation
- septum primum grows down from atrial wall
- ostium primum- gap below septum primum
- septum primum grows to endocardial cushion
- ostium secundum appears in middle to allow R > L shunt
- septum secundum grows down from atrial wall to right of septum primum»_space; creates foramen ovale
- RA pressure > LA pressure so foramen ovale remains open - R >L shunt in utero
What happens to foramen ovale after birth?
LA pressure > RA pressure
Septum primum presses against septum secundum
Foramen ovale closes
Where do most ventricular septal defects occur?
Membranous component of ventricles
Outline ventricular septation
- Membranous component grows down from endocardial cushions
- Muscular component grows up from muscular wall
- Both components meet to form septum
What are the derivates of the aortic arches?
1+2 - none
3 - common, internal + external carotid arteries
4 - aorta L + subclavian artery R
6- pulmonary arteries
Route of the right and left recurrent laryngeal nerves
- left: under arch of aorta
- right: under right subclavian artery
How is the aorta + pulmonary trunk formed?
Truncus arteriosus is divided by the outflow septum
What does Truncus arteriosus become?
Pulmonary trunk
Aortic arch
What is the physiological and pathological importance of the right auricle of the heart?
- physiological: muscular pouch that increases the RA capacity
- pathological: in AF patients, stasis of blood can occur > clot formation > stroke
