Cardio Embryo Flashcards by tia meechan

What embryological layer does the heart arise from?

Mesoderm (lateral splanchnic layer)

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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)

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At what point do vasculogenesis & angiogenesis, blood vessel development begin?

At the beginning of the 3rd week

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Where do vasculogenesis & angiogensis occur?

In the extraembryonic mesoderm of the yolk sac, allantois & chorion. (mesoderm gives rise to new vessels & heart structures)

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How does the heart tube form?

2 endothelial-lined channels (endocardial heart tubes) fuse together to form 1 heart tube during lateral folding

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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

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The SVC is developed out of what structure?

R common and anterior cardinal veins

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truncus arteriosus becomes what

Ascending aorta, pulmonary trunk

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bublis cordis becomes

Smooth parts of L and R ventricles

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Primitive ventricle becomes

Trabeculated portion of L and R ventricles

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primitive atrium become

Trabeculated portion of L and R atria

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L horn of sinus venosus becomes

coronary sinus

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R horn of sinus venosus becomes

Smooth portion of R atrium

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Endocardial cushion becomes

Atrial septum, membranous IV septum, AV and semilunar valves

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The IVC is developed out of what?

Posterior cardinal, subcardinal, supracardinal veins

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Primitive pulmonary vein becomes

Smooth portion of L atrium

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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

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what holds the heart tube in place in the pericardial cavity?

dorsal mesocardium

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heart tube layers and origins

endocardium (inner) - from angioblasts
myocardium (outer) - from cardiac myocytes

in between is cardiac jelly made by myocardium

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aortic sac forms

dorsal aortae (outflow tracts)

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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?

1. Hepatic segment: from hepatic vein & sinusoids 2. Prerenal segment: from R. subcardinal vein 3. Renal segment: from the subcardinal-supracardinal anastomosis 4. 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?

1. formation of septum primum 2. foramen and septum secundum form 3. 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