This site is 100% ad supported. Please add an exception to adblock for this site.

embryology-06-heart development


undefined, object
copy deck
When does heart first develop / first function
middle of third week, functions at beginning 4th week
why early heart development nec
repidly growing embryo can’t satisfy nutritional requirements via diffusion anymore – needs efficient method of acquiring oxygen & nutrients from maternal blood, & disposing of CO2 and waste
Cardiovascular system derived mainly from
splanchnic mesoderm (forms primordium of heart), paraxial and lateral mesoderm midway along hindbrain, & neural crest cells from between otic vessicles (primitive ears) and 3rd pair of somites
differentiation of blood early on?
none – same both into and out of heart – tube.
which three veins drain into the tubular 4th week heart
vitelline veins with poorly oxygenated blood from yolk sac, umbilical veins with well oxygenated blood from primordial placenta, and common cardinal veins returning poorly oxygenated blood from embryo body
what does the yolk stalk connect?
narrow tube between yolk sac and midgut
describe the early heart tube
polar, with a venous pole and an arterial pole. Heart tube has an outer myocardial muscular wall that secretes cardiac jelly which deforms when muscle contracts the inner layer is bounded by endocardium lumen – there is no outer epicardium
early heart tube works how?
myocardium contracts, squeezes jelly, compresses lumen to move blood
shape changes in heart caused by?
interaction between jelly and myocardium
in early heart tube, name chambers from caudally – cranially
sinus venosus (left and right horns, immediately above the 3 pairs of veins coming into heart tube), primitive atria, atrioventricular canal, primitive ventricle, ventricobulbar foramen, bulbus, bulbotruncal junction, truncus
what arises from the truncus
the aortic sac, which becomes the aortic arch
why does heart tube twist?
bulbus cordis and ventricle grow faster than other regions
what do the bulbus and ventricle first form
bulbo-ventricular loop
what occurs as a result of bending of the heart?
atrium and sinus venosus become dorsal to truncus arteriosus, bulbus cordis and ventricle
in the primitive heart, what is the future site of the AV valves?
atrioventricular canal
in the primitive heart, what is the future site of the Semilunar valves?
bulbo-truncal junction
review veins – cardinal veins drain what
blood from embryo
review veins – umbilicus drains what
review veins- vitelline drains what
yolk sac
of the two vitelline veins, which one persists?
when the superior cardinal veins anastamose, what do they become?
right cardinal becomes SVC, superior anastamoses between the two becomes the left brachiocephalic
what happens to the left cardinal vein
how does the sinoatrial orifice shift rightwards
shunting of blood to right causes it to move until it only communicates with right atrium
what does the right cardinal vein become
superior vena cava
what does the right vitelline vein become
inferior vena cava
what happens to the right umbilical vein?
by what day does the heart start beating
of vitelline veins, which persists?
what forms the left ventricle
primitive ventricle
forms right ventricle
what happens with veins near heart?
right sided veins persist, left sided veins disappear
right atrium comes from what?
sinus venosus (smooth) and primitive atrium (which is why right atrium has dual texture
which part of left atrium is formed by the primitive atrium
auricle (appendage)
what appears between the left sinus horn and septum primum
primary pulmonary vein
how does left atrium form
first sign of left atrium is appearance of primary pulmonary vein, which grows toward, and ‘cannibalizes’ walls of pulmonary veins, absorbing them to create its walls
what does the atrioventricular canal form
tricuspid and mitral valves
name of first septum to grow, and first opening init
septum primum and foramen primum
name of second opening, in which septum
foramen secondum in septum primum, as foramen primum is closing
septum primum is _______ than secondum
thinner, more membranous
where is the foramen ovalis located
posterior inferior wall of septum secondum
where does the majority of blood entering the fetal heart come from
placenta via the umbilical vein 70%
what supplies the second greatest amount of blood to the fetal heart?
superior vena cava, from head and arms (about 20%
how much blood does the heart receive itself?
about 3%
where does most of the blood leaving fetal heart go?
out pulmonary trunk, via ductus, to descending aorta 70%
what percentage of blood leaving the left bentricle goes to the head?
about 20%
how much blood leaving the heart goes out the aortic arch?
about 10% (remember, 60% or so is going out the pulmonary trunk, joining the 10% from the aortic arch, to go to abdomen and legs)
what is the percentage of blood going to L&R heart from IVC?
of the 70% coming into heart from IVC, 44% is going to the right side of the heart, 26% to the left side
how much blood goes to the heart itself and the lungs
very little – 3% to coronary circulation, about 7% to lungs
In addition to growth of muscular septum superiorly to separate ventricles, what other mechanism exists
downward growth of ventricles leaving muscular septum
what divides the truncus into the aorta & pulm. trunk
aorticopulmonary septum: (truncal bulbar cushions)
what closes off the interventricular muscular septum
the inferior portion of the aorticopulmonary septum
what is the upper portion of the interventricular septum
membranous septum
where is bundle of HIS
in membranous part of interventricular septum
what happens if there is a ventricular septal defect
can put patch over it but have to be careful not to stitch through bundle of HIS
what are the most common defects of the heart
what is fallotÂ’s teratology?
pulmonary stenosis, interventricular communication, hypertrophy of right ventricle – causes cyanosis (venous blood in systemic system) and dyspnea (problems breathing)
cure for fallotÂ’s teratology
blalock-taussig shunt – connect Left subclavian to pulmonary trunk (more blood to lung, collateral circ. serves arm)
Before birth all shunts are
right to left
blood shunts in one direction why
higher resistance oon pulmonary side – pulmonary arterioles tightly constricted – lungs not working yet. lower resistance on aortic-systemic side
what types of midline defects can occur in fetal heart
atrial septal, ventricular septal, persisting ductus arteriosus
what if shunts persist?
more blood goes to lungs – puts additional pressure on lungs, causes lung tissue to thicken irreversibly.
if pulmonary resistance keeps rising, what happens?
eventually will reach point that heart wonÂ’t be able to overcome the resistance
transposition of great arteries – consequences and fix
blue baby – insert atrial septal defect to cause lots of blood mixing in heart – repair properly when baby older.
aortic atresia and left ventricular hypoplasia meaning, consequences, fix.
no way out of aorta, left ventricle very small, unable to pump. Usually causes death. cure= heart transplant
morphologic right sided heart characteristics (no matter where actually appears)
SA node, sinus venosus, primitive atrium
right heart morphology – ventricle
moderator band
segmental analysis of chambers – look at:
appendage shape of atria, SA node? pulmonary veins?, ventricular trabeculae, moderator band, continuity (or not) of valves, great arteries: aorta-coronary arteries
what do lungs and heart have in common?
whatever atria do, lungs also do: eg: left type atria on right side, will be a left type lung.
situs ambiguous
two left atria, two left type lungs
situs inversus
sides switched
if ventricles match atrial type or not = atrioventricular ?
matches = concordance, doesnÂ’t = discordance

Deck Info