Development Flashcards
Why does the heart migrate from neck into thorax
because cardiogenic mesoderm migrates to cranial most part of the embryo
What does the heart tube arise from
paired endothelial lined tubes
at what end does the heart tube receive blood and pump blood
receives at the caudal end and pumps at the cranial end
When does cardiac looping begin and what are the 4 dilations
Day 22 bulbus cordis ventricle atrium sinus venosus
When does the heart start beating
Day 22
Why does the heart loop
ventricles grow faster than other regions
Which way does the cranial portion of the heart tube bend
ventrally, caudally and to the right
which way does the caudal portion of the heart tube bend
dorsally, cranially and to the left
What becomes of the sinus venosus
left sinus horn becomes coronary sinus
right sinus horn becomes part of right atrium as sinus venarum
What will the primitive atrium form
left and right auricles
What grows into the left atrium during final steps of development
the pulmonary vein
What is incorporated into the right atrium during final steps of development
sinus venosus
What will the primitive ventricle become
trabeculated portion of left ventricle
What are the 3 parts of the bulbus cordis
caudal, conus cordis and truncus cordis
what becomes of the caudal part of bulbus cordis
trabeculated region of right ventricle
what becomes of the conus cordis part of bulbus cordis
outflow of both ventricles, right= conus arteriosus and left=aortic vestibule
what becomes of the truncus arterioles part of bulbus cordis
pulmonary trunk and aorta
Describe pathway of blood in the developing heart around day 30
blood enters sinus venous-> primitive atrium -> primitive ventricle -> bulbus cordis ->aortic sac -> embryo
What week do coordinated contractions of the fetal heart begin
week 4
What is the first step of partitioning of the atrium
septum primum forms, day 30
What is the second step in partitioning of the atrium
ostium primum forms, day 30
what is the third step in partitioning of the atrium
ostium primum closes, day 33
What is the fourth step in partitioning of the atrium
ostium secundum opens via apoptosis, day 33
What is the fifth step in partitioning of the atrium
septum secundum forms, day 33
what is the sixth step in partitioning of the atrium
foramen ovale forms, because septum secundum is incomplete
What is the original septum primum known as in a newborn
the valve of foramen ovale
prenatally where is the pressure greatest in the heart
on the right side
postnatally where is the pressure gradient of the heart
on the left side
The heart valves form from what tissue type
neural crest cells, endocardial cushions
Why is the right ventricle not in contact with the atria like the left in development
bulboventricular flange regresses during week 5
What are the 2 portions of the interventricular septum. state their origins
muscular portion from mm of ventricle and membranous portion from endocardial cushions
When does partitioning of the ventricles take place
week 7
where are the conotruncal ridges derived form that form pulm trunk and aorta
neral crest cells
how many degress of spiraling do the conotruncal ridges undergo
180 degrees
what is the aorticopulmonary septum
spiraled conotruncal ridges
what does the conus cordis form
conus arteriosus and aortic vestibule aka right and left ventricles
what does the truncus arteriosus form
pulmonary trunk and ascending aorta
where do the semilunar valves form from
neural crest of conotruncal ridges
Ventricular septal defects account for what percent of congenital heart defects
30%
what are the 2 types of ventricular defect and which is most common
membranous- msot common
and muscular
the severity of a ventricular septal defect reflects what, and what is the usual result
size of defect and results in left to right blood shunting
Atrial septal defects account for what percent of congenital heart defects
10%
What are the various types of atrial SD
ostium secundum is too big
ostium primum- endocardial defect
common atrium- no atrial septum
what is the often result of ASDs
left to right blood shunting
What is the result of underdeveloped endocardial cushions
persitent atriocentricular canal
ostium primum defect
membranous interventricular septum defect
What percentage of congenital heart defects are Pulmonary and aortic valave stenosis
pulmonary- 7%
aortic 6%
What additional condition is likely with pulmonary and aortic valve stenosis
patent foramen ovale and ductus arteriosus
What causes tetralogy of fallot
unequal division of truncus arteriosus by conotruncal ridges
what are the 4 components of tetralogy of fallot
overriding aorta
pulmonary stenosis
ventricle septal defect
right ventricular hypertrophy
What causes transposition of Great vessels
conotruncal ridges fail to spiral
In a patient with transposition of the great vessels what else would you expect to see
patent ductus arteriosus and patent foramen ovale
What causes persistent truncus arteriosus
conotruncal ridges fail to form
What causes DiGeorge Syndrome
deletion on long arm Chromosome 22
What is the result of a long arm chrom 22 deletion
abnormal neural crest development leading to many cardiac abnormalities like defects of conotruncal formation
What are other signs of DiGeorge Syndrome
Craniofacial defects, thymic hypoplasia, parathyroid dysfunction- hypocalcemia, cleft palate CATCH22
What is dextrocardia
heart lies in right thorax
what causes dextrocardia
heart loops in opp direction
What causes ectopic cordis
failure of ventral body wall to close
what is ectopic cordis
heart lies on surface of chest
What do mesodermal cells differentiate into unde VEGF
blood islands
What do blood islands produce
hemangioblasts
They major embryonic arterial and venous systems arise via what process
vasculogenesis
What is the definition of angiogenesis
sprouting and growth of already existing vessels
What are the 3 primary vascular systems of the embryo/fetus
Intraembryonic
Yolk sac (vitelline)
Placental
What vessels are within the intraembryonic system
aortic arch aa and the cardinal veins
what vessels are within the yolk sac system
vitelline artery and vein
what vessels are within the placental system
2 umbilical aa and 1 umbilical vein
How many aortic arch pairs are there originally and where do they originate from?
6 pairs from aortic sac(truncus arteriosus)
Where do the aortic arch aa drain
dorsal aortae- paired cranially join caudally
What does the aortic arch become
proximal aortic arch and the brachiocephalic artery
What does the first aortic arch a become
regresses..maxillary a
what does the second aortic arch branch become
regresses (stapedial)
What does the third aortic arch artery become
common carotid aa
What does the 4th aortic arch aa turn into
R- R subclavian a
L- portion of aortic arch
What does the 5th aortic arch aa turn into
regresses completely
What does the sixth aortic arch aa turn into
R- pulmonary a
L- pulmonary a and ductus arteriosus
What does 7th intersegmental a turn into
R- part of right subclavian
L- left subclavian
What does the ductus arteriosus become in an adult
ligamentum arteriosum
Where does the right recurrent laryngeal n travel
loops around subclavian (4th branch) because 5 and 6 regress
Where does the left recurrent laryngeal n travel
loops around arch of aorta near ligamentum arteriosum
What do the vitelline aa become
celiac, superior mesenteric and inferior mesenteric aa
Where are the umbilical aa in an adult
off common iliac aa, supply placenta
turns into medial umbilical ligament
What is patent ductus arteriosus, results in?
ductus arteriosus does not close- blood shifts left to right and results in pulmonary hypertension
Which coarctation of the aorta presents at birth
preductal
why does postductal coarctation of the aorta usually present in early adolescence
collateral circulation is established between internal thoracic aa and intercostal aa prenatally
What causes retroesophageal right subclavian a
right 4th aortic arch degenerates, leaving 7th intersegmental a to form right subclavian
what is dysphagia lusoria
difficulty swallowing due to esophageal compression
What causes a double aortic arch
the right dorsal aorta between original of the 7th intersegmental a and fusion with dorsal aorta persists
does the double aortic arch usually cause constriction of esophagus
yes
What happens to the umbilical veins
right vein degenerates
left vein carries O2blood from placenta thorugh fetal liver to heart
What does the left umbilical v become
ductus venosus- bypass liver
What cardinal veins become the azygos system
supracardinal
What causes an absent inferior vena cava
right sub cardinal vein fails to make a connection with hepatic part of vena cava
where does the blood drain in an absent inferior vena cava
azygos system
what causes a left superior vena cava
left common cardinal vein persists and forms a left superior vena cava
right cardinal vein degenerates
Where does the superior vena cava drain if it is on the left
righ atrium via coronary sinue
what causes a double superior vena cava
left and right common cardinal vv persists
Where do the superior vena cavas drain if there is a double
right- into r atrium
left- via coronary sinus to r atrium
What does the lung bud give rise to
larynx, trachea, bronchi, bronchioles and alveoli
Where does the lung bud form form and when in development
week 4 from foregut as ventral diverticulum
What separates the lungbud from the esophagus
2 tracheoesophageal ridges
what to the tracheoesophageal ridges form when they fuse
septum
What occurs if there is an abnormal division of the cranial part of the foregut into respiratory and esophageal portions
tracheoesophageal fistulas
what is the most likely cause of a tracheoesophageal fistula
spontaneous deviation of the tracheoesophageal septum
What are other signs of a tracheoesophageal fistula
esophageal atresia(blind end) 90%, polyhydramnios, pneumonitis
What structure remains in contact with primordial laryngeal inlet after septum forms
pharynx and lung bud
Failure of the larynx to recanalize ocurrs in what time frame of development
between week 6 and 10
The trachea is fully developed by what week
12
describe timeframe of lung buds
week 5- lung bud divides into L and R
week 6- secondary bronchial buds
7th- tertiary bronchial buds
further branching continues postnatally
What is formed by dilation of terminal bronchi? what will the lungs look like.
congenital lung cysts, honeycomb appearance
Is abnormal division of the bronchial tree common
yes because little functional consequence
Weeks 5-16 what stage are the lungs in
pseudoglandular- terminal branches there bt no respiratory bronchioles hence not viable fetus
When do fetal breathing movements typically start
12th week development- amniotic fluid breathed in
Oligohydramnios affects the lungs how
lung hypoplasia
When is the canalicular stage of the lungs
16-26 weeks
When have the respiratory bronchioles and alveolar ducts formed
24 weeks
When do surfactant levels reach adequate amounts
26-28 weeks
Why are fetuses during weeks 26-28 only 50% viable
underdevelopment of alveoli
When is the terminal sac stage of lungs
26 weeks to 32 weeks
Fetuses born during terminal sac have what chance survival
80-95%
What are the two critical factors in derermining survival and growth of premature infants
sufficient surfactant production and adequate pulmonary vasculature
When is the aveolar stage of lung development
32 weeks to 8 years post natally
Why are lungs in newborns more dense in X rays
up to 300 million alveoli
Lack of surfactant production puts premature infants at risk of what syndrome
respiratory distress syndrome (hyaline membrane disease)
How can surfactant secretion be stimulated in utero
giving mom glucocorticoids
How can we treat lack of surfactant in postnatal babies
exogenous surfactant
Which structure carries oxygenated blood to the fetus
umbilical vein
