Cardio Embryo Flashcards
What embryological layer does the heart arise from?
Mesoderm (lateral splanchnic layer)
The heart & the great vessels come from what cell line?
Mesenchymal cells (multipotent stem cells that can differentiate into various cell types i.e. myocytes, adipocytes, osteoblasts)
At what point do vasculogenesis & angiogenesis, blood vessel development begin?
At the beginning of the 3rd week
Where do vasculogenesis & angiogensis occur?
In the extraembryonic mesoderm of the yolk sac, allantois & chorion. (mesoderm gives rise to new vessels & heart structures)
How does the heart tube form?
2 endothelial-lined channels (endocardial heart tubes) fuse together to form 1 heart tube during lateral folding
By the end of the 3rd week, what does the primodial CV system look like?
The heart is represented by the heart tubes & is joined by blood vessels from the embryo & extraembryonic membrane
The SVC is developed out of what structure?
R common and anterior cardinal veins
truncus arteriosus becomes what
Ascending aorta, pulmonary trunk
bublis cordis becomes
Smooth parts of L and R ventricles
Primitive ventricle becomes
Trabeculated portion of L and R ventricles
primitive atrium become
Trabeculated portion of L and R atria
L horn of sinus venosus becomes
coronary sinus
R horn of sinus venosus becomes
Smooth portion of R atrium
Endocardial cushion becomes
Atrial septum, membranous IV septum, AV and semilunar valves
The IVC is developed out of what?
Posterior cardinal, subcardinal, supracardinal veins
Primitive pulmonary vein becomes
Smooth portion of L atrium
what are the steps of the heart tube forming?
splanchnic layer of lateral mesoderm is stim by VEGFs from endoderm to form:
inner mesoderm (hemocytoblast) > RBCs, WBCs
outer mesoderm (angioblast) > BVs, heart tubes
lateral folding fuses heart tubes and pericardial cavities into one of each
during whole process, craniocaudal folding also happens to move heart from head to thorax and INTO pericardial cavity
what holds the heart tube in place in the pericardial cavity?
dorsal mesocardium
heart tube layers and origins
endocardium (inner) - from angioblasts
myocardium (outer) - from cardiac myocytes
in between is cardiac jelly made by myocardium
aortic sac forms
dorsal aortae (outflow tracts)
flow of blood through heart tube
sinus venosus > PA > PV > bulbis cordis, truncus arteriosis > aortic sac > dosral aortae
aortic arch derivatives:
1: maxillary (branch of ext carotid)
2: stapedial, hyoid
3: common carotid, proximal int carotid
4: aortic arch (left) + proximal right subclavin (right)
6: proximal PAs (both sides) and ductus arteriosus (left only)
at what week does the heart beat spontaneously? when is polarity established?
week 4; first functional organ in vertebrate embryos
left-right polarity starts to establish at wk 4 also
the asc aorta and pulmonary trunk are formed from what
- Bulbar ridges fuse & become an aorticopulmonary septum
- Aorticopulmonary septum divides the bulbus cordis & the truncus arteriosus into 2 arterial channels
- These 2 channels become the aorta & PT
arise from neural crest cell migrations
aortic and pulmonary valves are formed from
endocardial cushions of outflow tract
mitral/tricuspid valves are formed from
fused endocardial cushions of AV canal
What 4 main segments compose the IVC?
- Hepatic segment: from hepatic vein & sinusoids
- Prerenal segment: from R. subcardinal vein
- Renal segment: from the subcardinal-supracardinal anastomosis
- Postrenal segment: from the supracardinal vein
The aorta & pulmonary trunk are formed when in gestation?
Between week 5 & 6
At what point can a fetal heart beat be detected by a Doppler?
7 weeks after menses (week 5 in fertilization age terms)
3 shunts of fetal circulation
Umbilical vein > joins L portal v via ductus venosus > joins hepatic v into IVC to bypass liver
oxygenated blood reaching heart via IVC goes through foramen ovale
deoxy blood from SVC goes through RA > RV > PA > ductus arteriosus > desc aorta
The embryonic foramen ovale becomes what after birth?
Fossa ovalis (shunted blood from R. atrium to L. atrium)
The embryonic ductus arteriosus becomes what after birth?
Ligamentum arteriosum (shunted blood from PT into aorta)
What forms the atria?
The separation into right and left of the primitive sinuatrium or septum primum
The fusion of the endocaridal or atrioventricular cushions posteriorly & anteriorly forms what?
Tricuspid & mitral inlets which become the AV valves
HOw does the right & left ventricle become compartmentalized?
2 theories:
1. Trabeculations appear & grow into muscular structures –> coalesce w/ the endocardial cushions –> form IV septum eventually
2. At the apex a primordial muscular IV ridge grows –> fuses w/ the walls of the ventricles –> grows up to the endocardial cushion –> forms IV foramen
What does the interventricular foramen result in?
By the end of week 7, it closes resulting in the IV septum
The umbilical vein becomes what?
Ligamentum teres hepatis (round ligament of the liver)
The vitelline veins become what?
Portal circulation and mesenteric veins
The left and right dorsal aorta become what?
descending aorta
What is the normal physiological process by which truncus arteriosus transforms into asc aorta and pulmonary trunk?
How can this process go wrong? What pathology are associated?
- neural crest cell migration from hindbrain
- aorta and PA undergo spiral formation > AP septum formed
Pathology: persistent TA
- incomplete AP septum formation due to failure of neural crest cell migration
- leads to mixing of oxygenated + deoxygenated blood
- associated with DiGeorge Syndrome, SCID
Pathology: transposition of great vessels
- failed AP septum spiraling > reversal of PA and aorta
- 2 paralell circuts with deoxygenated blood going in and blood being pumped back out before being oxygenated
- RV > aorta, LV > PA
- incompatible w life without shunts or keeping PDA open; associated with diabetic mothers
What are the steps in atrial septation?
- formation of septum primum
- foramen and septum secundum form
- foramen ovale closes
From where does the septum primum form during atrial septation?
Forms inferiorly from superior primitive atria
What is the Foramen primum/ostium?
An opening between the septum primum and AV cusions/rest of atria
Explain the formation of foramen and septum secundum during atrial septation
foramen secundum forms with septum primum
septum secundum forms as a superior and inferior segment
opening between septum primum and secondum = foramen ovale
What causes the closure of foramen ovale?
first breath at birth =
more oxygen > dilation > dec pulmonary vasculature resistence > inc LA pressure + dec RA pressure (more blood in pulmonary vesssels) > inc pressure closes opening
What defect can occur during atrial septation?
patent foramen ovale (PFO) - failure of septum primum and secondum to fuse after birth
mostly asx
inc in RA pressure can open PFO
clots/DVTs can > SVA or paradoxical embolism bc can pass onto left side of heart and go to brain
Ventricular septal defects are usually due to defects in which portion of the IV septum?
Membranous
What types of atrial septal defects can occur?
persistent shunt (whereas PFO is intermittent flap) > wide fixed split S2
secondum type - most common, usu isolated (hypo-/aplasia)
primum: usu occurs with other heart defects
What can result from defects of the 4th aortic arch?
4th arch: aortic arch (L), prox r subclavian (R)
coarctation (narrowing) of the aorta
What can result from defects of the 6th aortic arch?
6th: prox PA (R/L), ductus arteriosus (L)
PDA: due to PG
RF: premature
continuous machine line murmur in left infraclavicular/2nd intercostal space
palpable thrill
