Cardiorespiratory Development Flashcards
mesoderm types
paraxial, intermediate, lateral plate
and cardiac type (sort of a fourth type)
cardiac mesoderm
goes to cranial portion of embryo
-in cardiogenic field
two folds
lateral and head tail
head tail fold pulls the cardiogenic region into thorax
cardiac crescent
mesoderm organized into two tubes
lateral fold puts two heart tubes together
-they fuse
endocardial tube
fusion of two tubes
gives rise to all of heart
-except fibrous skeleton and heart valves
blood flow in primitive heart?
caudal - venous
cranial - arterial
around day 22?
starts beating and actually contracts
differential of heart tube?
caudal > cranial
sinus venosus, atrium, ventricle, bulbus cordis
cardiac looping
ventricles grow rapidly, cause heart to fold
cranial - ventral, caudal, to the right
caudal - dorsal, cranial, to the left
sinus venosus
incorporated into right atrium as sinus venarum
major venous end of heart
-to right atrium
left sinus horn regresses
left sinus horn
forms coronary sinus
venous drainage of heart
left atrium smooth portion
from pulmonary vein
primitive atrium
lined with pectinate muscles
auricles of left and right atrium
sinus venarum
right atrium
primitive ventricle
only forms trabeculated portion of left ventricle
three regions of bulbus cordis
1 trabeculated part of right ventricle
2 conus cordia
3 truncus arteriosus
conus cordia
forms smooth walled outflow tracts of both left and right ventricles
-aortic vestibule of left V and conus arteriosus of right V
truncus arteriosus
forms the two great arteries
- pulmonary trunk from right V
- aortic artery from left V
blood flow through primitive heart?
sinus venosus
primitive atrium
**
partitioning of heart
where most of anomalies take place**
-starts around day 30
-forms septa
prenatal heart
needs to shunt blood away from developing lungs**
lungs not functioning, but they are highly vascularized
ductus arteriosus
arterial blood shunt
what diverts blood around right ventricle?
foramen ovale
ductus arteriosus
**these must close immediately at birth
osteum
means opening
step 1 partitioning
septum primum forms in common atrium
mostly fibrous
first partition - separates right and left atrium
step 2 partitioning
ostium primum forms
-eventually closes and will fuse with atrioventricular septum
steps 3 and 4 or partitioning
as ostium primum closing, second opening (ostium secundum) forces cell death in septum primum
step 5 partitioning
septum secundum forms within right atrium
-thick and muscular
forms interartial septum
step 6 partitioning
septum secundum is incomplete
-its foramen is foramen ovale
-original septum now referred to as valve of foramen ovale
prenatally and postnatally
pre-
high pressure right side
low pressure left side
blood shunted through foramen ovale
post-
lower pressure right atrium
higher pressure left atrium
valve of oval foramen closes
septum primum and septum secundum
will fuse
patent foramen ovale
septum primum never fuses to secundum
asymptomatic - it is closed, so it functions, but it just doesn’t fuse
pressure on right side of heart can open it up
bulboventricular flange
regresses and allows opening of atrioventricular canal
so RA and RV, LA and LV can communicate
bulboventricular flange
regresses and allows opening of atrioventricular canal
so RA and RV, LA and LV can communicate
endocardial cushion
superior and inferior and two lateral parts
superior and inferior will fuse (AV septum)
-left and right halves
heart valves
form from neural crest
interventricular septum
muscular portion from muscle of ventricle wall
membranous portion from endocardial cushions
conotruncal ridges
left and right
will fuse to form conotruncal septum
separates outflow tract of heart
it spirals**
caudally to cranial 180 degrees
importance of spiral
so right ventricle - pulmonary trunk
and left ventricle - aorta
if doesn’t spiral - transposition of the great vessels**
neural crest disorder?
heart valve issues
cardiac defect
most common congenitally
VSD
ventricle septal defects (hole in the heart ventricle)
in the interventricular septum
- muscular type
- membranous type (more common)
symptoms depend on size of hole
will get left-right shunting of blood
- pressure higher on left side postnatally
- increased pulmonary blood flow
- decreased systemic blood flow
ectopic cordis
body wall defect
thoracic wall doesn’t fuse
heart herniates and forms externally
ASD
atrioseptal defect (hole in heart atrium)
osteum secundum - cell death
1 excessive resorption of septum primum - lose valve, can’t close foramen ovale
2 septum secundum doesn’t close
left to right shunting of blood
endocardial cushions form?
AV septum
part of atrial septum (closes ostium primum)
membranous part of interventricular septum
endocardial cushion defects
neural crest defects
results in:
1 persistent AV canal
2 ASD
3 VSD
endocardial cushions form?
AV septum
part of atrial septum (closes ostium primum)
membranous part of interventricular septum
pulmonary, aortic stenosis
narrowing of vessels
due to abnormal valves
tetralogy of fallot
conal truncal ridges form and spiral - but don’t equally divide (large aorta and small pulmonary trunk)
four features always present** 1 pulmonary stenosis (narrowing) 2 overriding aorta (very large) 3 hypertrophy (right ventricle) 4 VSD (membranous)
right ventricle hypertrophy - because of pulmonary stenosis
one of most common causes of cyanosis in newborn
transposition of the great vessels
conal truncal ridges don’t spiral
aorta on right side
pulmonary on left side
persistent truncus arteriosus
conotruncal ridges fail to form
cyanotic infant
mixing of blood because aorta and pulmonary arteries are all together
dextrocardia
pretty rare
right sided heart
ectopic cordis
body wall defect
thoracic wall doesn’t fuse
heart herniates and forms externally
di-george syndrome
chromosome 22 deletion
neural crest disorder
CATCH-22
Cardiac defects Abnormal facial features Thymic aplasia Cleft palate Hypocalcemia (parathyroid deficiency)
one question on exam
from one of the questions on the development of vascular system slide*****
two ways vessels form
vasculogenesis
angiogenesis
vasculogenesis
de novo synthesis of brand new vessels
aortic arch arteries and cardinal veins
angiogenesis
postnatally
sprouts from already formed
VEG-F
main signalling molecule
signals mesoderm to form blood islands which becomes vessel
fetal vasculature?
yolk sac
umbilical
fetus
major arteries of fetus
aortic sac aortic arches (6 pairs) dorsal aorta
major veins of fetus
cardinal veins (anterior, posterior to common)
umbilical vein
vitelline vein
yolk sac system
gone by week 12
-vitelline vein and vitelline artery
placental system
two umbilical arteries (to placenta)
one umbilical vein (oxygenated back to heart)
aortic arches
truncus arteriosus > aortic sac
aortic sac gives off 6 pairs (right and left)
form cranial to caudal in the neck
drain to dorsal aorta (left and right)
-thorax they fuse to form dorsal aorta
what happens?
arch 1 regresses
dorsal aorta between 3 and 4 on L and R regresses
-forms cranial and caudal blood suppliers
right branch of dorsal aortic artery regresses
arch 1, 2 and 5 regress on L and R
arch 3 - forms common carotid artery L and R
arch 4 - forms right subclavian (right side) and arch of aorta (left side)
arch 6 - ductus arteriosus (second blood shunt) on left / right regresses
arch 3
forms common carotid artery L and R
-main arteries to head and neck
arch 4
forms right subclavian side (right)
forma aortic arch (left)
arch 6
right regresses and left forms ductus arteriosus
look at the final organization
in notes**
ductus arteriosus
second blood shunt
- blood from pulmonary trunk goes to aorta
- so it skips lungs
postnatally ductus arteriosus
closes, becomes ligamentous
ligamentum arteriosum
recurrent laryngeal nerves
forms with aortic arch apparatus
-forms in neck and pulled to thorax by heart
given off by vagus nerve
at level of 6th arch to get to larynx
right recurrent laryngeal nerve?
loops under right subclavian
left recurrent laryngeal artery?
loops under aortic arch
under ductus arteriosus (from left 6th arch)
patent ductus arteriosus
ductus arteriosus doesn’t close
-left to right blood shunt (from aorta to pulmonary system)
coarctation of the aorta
constriction of aorta
preductal - proximal to ductus arteriosus
-infantile (at birth, bypass closes)
postductal - distal to ductus arteriosus
- adolescent (intercostal arteries become huge)
- get blood back to aorta
- upper limb HTN, lower limb low BP
retroesophageal right subclavian artery
right subclavian that passes posterior to esophagus
- 4th aortic arach regresses
- intersegmental forms subclavian - growth puts it behind
can cause dysphagia lusoria
dysphagia lusoria
difficulty swallowing because of vessel
double aortic arch
constrictive loop around esophagus
-will frequently see dysphagia
get a right and left aortic arch
respiratory diverticulum
aka lung bud
forms lungs
tracheoesophageal septum
between trachea and esophagus
formation of this septum is cause of fistula
fistula
abnormal opening between two structures
tracheoesophageal fistula
septum deviates through esophagus
- proximal ends blindly
- distal fistula ends in trachea
babies can’t eat, immediately regurgitate
stomach distended (full of air)
larynx
upper portion of lung bud
week 5 lungs
to primary bronchi
then secondary, tertiary, bronchioles, alveolar ducts
walls get progressively thinner
pseudoglandular stage
week 5 - 16
lung not functional
have terminal bronchiole
canalicular stage
week 16-26
survivability increases rapidly
have respiratory bronchioles (capable of air exchange)
have surfactant
surfactant
if its there, you can survive!
terminal sac stage
week 26 weeks to birth
capable of respiration
survivability increases rapidly
alveolar stage
week 32 weeks to 8 years old
form alveolus
respiratory distress syndrome
not enough surfactant
- alveoli can’t open
- too much surface tension
can give glucocorticoids to mother
-will stimulate surfactant
fetal circulation
compare prenatnal and postnatal circulation
