Embryology Flashcards
from what type of tissue does the heart develop from
cardiogeneic mesoderm
this migrates in early development to the cranial-most extent of embryo
what is clinically significant about the heart forming at the cranial most extent of the embryo
as it develops, it pulls its innervation supply from the cranial portion
cervical branches of the vagus nerve and sympathetic chain innervate the heart b/c of the long migration into the thorax
what structures in the heart do the neural crest cells form?
heart valves and fibrous skeleton
how does the heart tube form?
what happens when the embryo begins to fold laterally?
initially forms as paired endothelial lined tubes
as the embryo folds laterally the paired tubes fuse forming one continuous heart tube
initially in the heart tube, what end is receiving venous blood and what end is pumping arterial blood to the body
receives venous blood at the caudal end and pumps arterial blood at the cranial end
as the heart begins to cardiac loop, what are the four original dilations
bulbus cordis
ventricle
atrium
sinus venosus
what actually causes the heart to loop
why is it important for the heart to loop
the ventricles grow faster than other regions
brings the heart into its normal heart position, brings regions of the linear heart tube into contact with regions its didn’t have before (ventricular region to the cranial bulbus cordus)
in which direction does the cranial portion loop
bends ventrally, caudually and to the right
in which direction does the caudal portion loop
dorsally, cranially and to the left
what is the sinus venosus composed of?
what are the common veins it receives
left and right venous horns
receiving blood from major veins
each side receives 3 veins
common cardinal vein (blood from body of embryo)
umbilical vein (oxygenated blood back from placenta)
Vitelin vein (nutritional support back from the yolk sac)
what does the left sinus horn (of the sinus venosus) form
coronary sinus
it regresses quite a bit and then forms the coronary sinus
what does the right sinus horn become incorporated into?
the right atrium as the sinus venarum
smooth walled portion of the right atrium
what does the primitive atrium form
the auricles of right and left atria
what are the final steps in development of right atrium
sinus venosus is incorporated into the right atrium and forms the sinus venarum
the original embryonic atrium forms the atrial auricle
what are the final steps in the development of the left atrium
proximal portions of pulmonary veins are incorporated into left atrium and forms smooth walled portion of the chamber
just doesn’t have a special name like the sinus venarum
what will the primitive ventricle from
the trabeculated portion of the left ventricle
when does the heart begin beating
day 22
what are the 3 portions of the bulbubs cordis
caudal portion conus cordis (mid portion) truncus arteriosus (cranial portion)
what will the caudal portion of the bulbus cordis form?
trabeculated region of the right ventricle
what will the conus cordis of the bulbus cordis form
forms the smooth-walled outflow region of both ventricles
in the right ventricle this is the –> conus arteriosus
in the left ventricle this is called the –> aortic vestibule
what does the truncus arteriosus (cranial portion) of the bulbus cordis form
pulmonary trunk and ascending aorta
what is the circulation through the primitive heart
sinus venosus–> primitive atrium–> primitive ventricle–> bulbus cordis –> aortic sac–> embryo
why must partitioning of the heart take place?
in order to keep blood away from the lungs
what does ostium mean?
opening
what is the first step in partitioning of the heart
septum primum forms
this is a thin membranous septum
what is step two of partitioning of the heart
Ostium primum forms Short-lived Fuses with developing Atrio ventricular septum Gone by day 33
what is step 3 and 4 of the partitioning of the heart
As the ostium primum is closing (3), a second opening (ostium secundum) forms from cell death in septum primum. (4)
what is step 5 of the partitioning of the heart
Septum secundum forms within right atrium
Major contributor to intra-atrial septum.
what is step 6 of the partitioning of the heart
Septum secundum is incomplete. Its foramen is called the foramen ovale.
the septum primum becomes the valve of the foramen ovale
blood from the right atrium goes right to the left atrium bypassing the right ventricle
prenatally where is there greater pressure in the heart and why is this relevant
greater pressure in the right side of the heart
thus blood bypasses the right ventricle via the foramen ovale
postnatally where is there greater pressure in the heart and why is this relevant
pressure is greater in the left side of the heart closing the valve of the foramen ovale against the septum secundum and thus forming the fossa ovalis
what is patent foramen ovale
occurs in 25 percent of population
results when the valve of the foramen ovale does not completely fuse to the septum secundum
usually asymptomatic
however, any increase in pulmonary pressure (coughing, sneezing, pulmonary hypertension) can cause the foramen ovale to re-open and a shunting of blood from right to left
initially in the partitioning of the atrioventricular orifice what is the atria in contact with only
the primitive left ventricle
what is separating the right ventiricle from the right atria initially
bulboventricular flange
when does the bulboventricular flange regress and what else is happening at the same time?
what do these two events provide?
Bulboventricular flange regresses during 5th week; at the same time the
atrioventricular canal enlarges and shifts to the right.
d. These two events provide communication of atria with left and right ventricles.
what are endocardial cushions derived from?
what do these do
NEURAL CREST CELLS
Superior and inferior endocardial cushions project into the atrioventricular canal
and fuse, separating the AV canal into right and left orifices.
from what do atrioventricular valves form from?
Atrioventricular valves form from neural crest of endocardial cushions.
what is the muscular portion of the interventricular septum derived from?
muscle of the ventricle walls
what is the membranous portion of the interventricular septum derived from
endocardial cushions (neural crest cells)
what are the conotruncal ridges derived from?
neural crest cells
what do the semilunar valves form from
neural crest cells and conotruncal ridges
why is it important that the conotruncal ridges spiral
Makes it so that the right ventricle pumps out throught pulmonary trunk and the left ventricle pumps out through the aortic channel
transposition of the great vessels could happen if this step doesn’t happen
contruncal ridges fuse to form what?
what does the conus cordis form
what does the truncus arteriosus form
aorticopulmonary septum (spiral septum).
a. Conus cordis forms conus arteriosus (right ventricle) and aortic vestibule (left
ventricle) .
b. Truncus arteriosus forms pulmonary trunk and ascending aorta.
what are VSD’s
which type are the most common
what is the result of these
Ventricular septal defects (VSDs)
- Membranous septal defect (most common)
- Muscular septal defect
- Severity depends on size of defect; often results in left-to-right blood shunt
pumonary HTN
left ventricular hypertrophy because there is decreased systemic flow
what are ASD’s
atrial septal defects
what are the types of ASD’s
ostium secundum defect ostium primum defect common atrium (complete loss of atrial septum and this is almost always associated with other major heart defects)
causes left to right shunt
what are the possibilities that can go wrong with ostium secundum
it is a Large opening between left and right atria
b. Cause: excessive degeneration of septum primum
c. Cause: insufficient proliferation of septum secundum
what are the problems with ostium primum
endocardial cushion defect
what 3 structures does the endocardial cushions form
Atrioventricular septum
part of atrial septum (closes ostium primum)
mebranous interventricular septum
what are the 3 things endocardial cushion defects result in?
Persistent atrioventricular canal
ASD (ostium primum defect)
Membranous VSD
how does pulmonary/aortic valve stenosis occur because of a congenital defect
Pulmonary trunk or aorta very narrow or completely occluded due to malformation
of semilunar valve.
- Often present with both patent foramen ovale and ductus arteriosus.
why does transposition of the great vessels happen?
Cause: conotruncal ridges fail to spiral.
- Aorta arises from right ventricle.
- Pulmonary trunk arises from left ventricle
- Usually occurs with patent ductus arteriosus, patent foramen ovale
what is the cause of persistent truncus arteriosus
conotruncal ridges fail to form due to neural crest cell problem
Undivided truncus receives blood from right and left ventricles
Usually occurs with patent ductus arteriosus, patent foramen ovale
what is DiGeorge Syndrome
Cause: deletion on long arm of Chromosome 22.
2. Abnormal neural crest development***
- Cardiac abnormalities (usually defects of conotruncal ridge formation which means persistent truncus arteriosus and valve defects)
- Craniofacial defects (cleft palate)
- Thymic hypoplasia (recurrent infections)
- Parathyroid dysfunction (hypocalcemia)
what is dextrocardia
Heart loops in opposite direction; lies in right thorax (a mirror image).
what is ectopic cords
Results from failure of ventral body wall to close
2. Heart lies on surface of chest
what are the two ways that blood vessel development occur
vasculogenesis
de novo
angiogenesis (sprouting of growth of alreayd existing vessels)
what is the signal for mesodermal cells to differentiate into blood islands
VEGF
blood islands give rise to hemagioblasts
the major embryonic arterial and venous systems arise via vasculogenesis
what are the 3 primary vascular systems of embryo/fetus
intraembryonic system
yolk sac system
placentaal system
what is the intrembryonic system
aortic arch arteries
cardinal system of veins
what is the yolk system
vitelline artery
vitelline veins
what is the placental system in the embryo
umbilical arteries 2
umbilical vein 1
what are the major arteries in the embryo
aortic sac arotic arches dorsal arches umbilical arteries vitelline artery
