Embryology Flashcards
- What structure arises from the primitive pharynx?
- What structure arises from the structure in the first question?
- What germ layers are these derived from?
- larnygotracheal groove gives rise to…
- laryngotracheal diverticulum (lung bud)
- endoderm
What parts of the respiratory tract arise from endoderm?
pulmonary epithelium
glands of larynx, trachea, bronchi
What region of the mesoderm are respiratory components derived from?
lateral plate mesoderm
The lateral plate mesoderm splits to give rise to..
splanchic mesoderm
somatic mesoderm
What is the visceral pleura derived from?
splanchnic mesoderm
What is the CT, smooth muscle, and cartilage of the respiratory tract derived from?
splanchnic mesoderm
what is the parietal pleura derived from?
somatic mesoderm
What is the role of the tracheoesophageal septum?
divides the trachea and esophagus at the origin point of the laryngotracheal diverticulum
What is the mechanism of error in the division of the tracheoesophageal septum?
decreased proliferation of endoderm
What is esophageal atresia? symptoms?
a blind esophagus due to errors in the tracheoesophageal septum
What is a tracheoesopheal fistula?
an abnormal connection between the trachea and esophagus, usually accompanied by esophageal atresia
What secondary condition arises from tracheoesophageal fistulas? why does this occur?
polyhydramnios (excess amniotic fluid)
normally the amniotic fluid is ingested and transferred to the placenta, but the fetus is unable to ingest anything so the fluid builds up
When do the primary bronchi form off of the respiratory bud? what direction do they grow?
week 4
grow caudal/ventral
when do the primary bronchi split to become secondary (lobular bronchi)?
week 5
when do the secondary bronchi split to become tertiary?
week 7
when are the bronchopulmonary segments done branching and how many orders of branching occur?
week 24
17 orders of branching, 7 more after birth
When is the psudeoglandular stage of development?
weeks 5-17
what occurs in the pseudo-glandular stage of development? can the fetus survive at this stage?
endodermal tubes –> terminal bronchioles
(looks like exocrine glands)
not compatible with life
when is the canalicular stage?
weeks 16-25
what occurs in the canalicular stage? can it surive?
terminal bronchioles –> respiratory bronchioles –> alveolar ducts (primordial alveolar sacs)
maybe able to survive
when is the terminal sac stage?
Week 24-birth
what occurs during the terminal sac stage?
alveolar ducts –> alveolar sacs
alveoli form as epithelium thins
type I and II pneumocytes form
gas exhange can occur
when is the alveolar stage?
week 32-age 8
what occurs in the alveolar stage?
terminal sacs –> adult alveoli
primitive alveoli form and continues till age 9
what cells produce surfactant and what is its role?
type II, reduces surface tension and prevents collapse of small alveoli
what splits to form the intraembryonic coelem?
lateral plate mesoderm forms somatic (dorsal) and splanchic mesoderm (ventral) with cavity in between
How is are the two intraembryonic coelem brought together to form one big cavity?
lateral folding
what is the arrangement of structures in the intraembryonic cavity after folding?
inside of body wall covered by parietal peritoneum
gut tube is covered in visceral peritoneum and suspended by dorsal mesesentary
note: remember lungs butt out from the gut tube at the layrngotracheal groove and grow into this cavity thats formed
What moves the pericardial ceolum and septum transversum ventrally?
head ventral folding, brain grows over and pushes structures downward
What are the parts of the intraembryonic ceolum after folding and where are they located?
pericardial coelum-ventral to heart tube, cranial to septum transversum
pericardioperitoneal canal=two tubes running along the ventral portion of the fetus connected to the pericardial coelum
what does the pericardial-peritoneal canal become?
pleural cavities, peritoneal cavities
what separates the pericardial cavity from the pericardial-peritoneal canal?
the pleuropericardial folds
how do the pleuropericardial folds seperate the pericadial cavity from the pericardial-peroneal canal?
it grows medially from the somatopluera and becomes a pleuropericardial membrane separating the two cavities
lungs then grow ventrally and carve out the rest of the cavity
what does the pleuropericardial membrane become?
fibrous pericardium
What affect does oligohydraminos have on lung development?
decreases hydraulic pressure on developing lungs
impairs stretch receptors and lung growth
results in pulmonary hypoplasia
what causes respiratory distress syndrome? what are some buzzwords to narrow this down?
shitty type II pneumocytes that makes them incapable of producing surfactant
rapid labored breathing shortly after birth
“glassy membrane lungs”
“hyaline membrane lungs”
What causes a congenital lung cyst?
dilation of terminal bronchioles with air or fluid
what is pulmonary agenesis and what causes?
absence of lung growth
respiratory bud fails to split
How do the pericardioperitoneal canals close?
pleuroparietal membrane grows ventrally and fuses with septum transversum
At what week do we see definitive pleural and peritoneal cavities?
week 7
what are the components of the diaphragm?
septum transversum (central tendon)
pleuroperitoneal membranes
musuclar ingrowth from body walls
what issues arise from pericardioperitoneal canal closure?
congenital diaphragmatic hernia
what side do congenital diaphragmatic hernias usually occur?
left side, visceral bulge into pleural cavity
what is an angioma?
bening growth of blood vessels and lymphatic capillaries
What germ layer gives rise to early cardiogenic precursors?
splanchnic mesoderm –> angiogenic clusters (endothelial precursor cells) –> endocardial tubes and pre cardiomyocytes
What structures arise from the primary heart field?
R/L atria, L ventricle
What structures arise from the secondary heart field?
R ventricle, outflow tract
What causes the two heart tubes to fuse together at midline to become one cardiac tubes?
lateral folding
What are the three layers of the single heart tube and what do they arise from?
Endocardium from endothelial precursor cells
cardiac jelly= Splanchnic mesoderm
myocardium from precardiomyocytes
What degenerates giving rise to the transverse sinus?
dorsal mesocardium
what gives rise to the epicardium
proepicardial organ (From splanchnic)
How does the heart get from the cranial end and what is its position after this event?
cranial folding
it is cranial to the septum transversum, suspended in the body cavity via the dorsal mesocardium
How is the primitive heart tube attached after folding?
outflow tract attached cranially, inflow tract attached caudally
when does cardiac looping occur?
week 4
Explain cardiac looping, why does this occur?
continued growth of the heart tube, but since its fixed at its cephalic and caudal ends, it folds and loops, moving the primordial ventricles to ventrally and to the right
what role does the secondary heart field play in cardiac looping?
these cells are inhibited by the notocord until lateral folding occurs, then secretes growth factors that contribute to the lengthening of the tube
What are the definitive regions of the early heart after cardiac looping?
superior region connected to venous sinus will become atria
inferior region connected to outflow tract will become ventricles
What is the path of oxygenated blood in fetal circulation?
umbilical vein –> ductus venosus –> right atrium –> foramen ovale –> left atrium –> left ventricle –> aorta
(some mixing occurs in right ventricle)
What is the path of deoxygenated blood in fetal circulation?
SVC –> RA (some mixing with oxygenated)–> right ventricle –> pulmonary trunk –> ductus arteriosus (bypasses pulmonary circulation –> descending aorta –> out
What is dextrocardia? what is the cause?
reversal of ventricles
errors in cardiac looping
What is situs invertus?
total reversal of all internal organs
What is situs ambiguous?
partial reversal of internal organs
What is visceroatrial heterotaxia?
a type of situs ambiguous where the heart is on the right and GI is normal
Describe the primitive venous inflow into the sinus venosus
3 bilaterally symmetrical veins
R/L vitelline
R/L umbilical
A/P cardinal
How is the primitive venous inflow remodeled so all venous return goes to right atrium?
left to right shunting
What is the fate of the R and L vitelline veins?
right becomes hepatic portal system
left regresses
What is the fight of the R and L umbillical veins?
Right-regresses and becomes r umbilical ligament
Left-proximal part regresses, distal connects to ligamentum teres hepatis
What is the fate of the anterior cardinal veins?
left to right shunting forms a branchiocephalic anastomosis and later remodeling to become the SVC on the right
What is the fate of the posterior cardinal veins?
Supracardinal and subcardinal veins add on
left to right shunting turns them into the IVC
also supracardinal becomes azygos and hemiazygos i guess
What features arise when sinus venosum is incorporated into the wall of the R atrium?
crista terminalis
right horn of sinus venosus=smooth part of right atrium
left horn of sinus venosus=coronary sinus
What is the crista terminalis?
interior of the atrial wall that separates the smooth and rough parts
WHAT IS THE SINUS VENARUM?!?!?
smooth part of right atria formed from right horn of sinus venosus
What two processes result in cardia septa formation?
- endocardial cushion formation (contributes to membranous part)
- differential growth (muscular growth of septum)
Where does endocardial cushion tissue come from?
outgrowth of endocardium
what part of the septa does endocardial cushion contribute to?
membranous inter-ventricular septum and atrial septum
How is the AV septum formed? How does this lead to formation of AV canals? are neural crest cells involved in this process?
endocardial cushion tissue grows from ventral and dorsal sides and meet in middle
lateral parts dont fuse and are the AV canals
NO NCC
What closes off the outflow tract?
conotruncal endocardial cushion AND NCC
What occurs in a persistent AV canal? cause? symptoms? what is it commonly associated with?
failure of endocardial cushion cells
results in an ASD and VSD
sx: pulmonary HTN, intolerance to exercise, SOB, cardiac congestion
downs syndrome
Describe how the atria are divided (sorta long but deal with it)
- Septum Primum and dorsal mesenchymal protrusion grows from dorsal to ventral towards endocardial cushion, hole in it is foramen primum
- Foramen primum closes, foramen secundum opens
- Septum secundum develops and covers most of the foramen secundum
- Remaining opening for foramen secundum is now foramen ovale
What keeps foramen ovale open during fetal times?
greater pressure in RA vs LA because pulmonary circulation doesn’t exist yet
What congenital abnormalities result in cyanosis? (5 Ts
- truncus arteriousis (persistant)
- transposition of great vessels
- tricuspid atresia
- tetrology of fallot
- TAPVR
VSD>ASD>PDA
What causes cyanosis? what would cause early cyanosis vs late?
lack of oxygenated blood
mixing of oxygenated and deoxygenated blood
early=right to left
later=left to right
How does the foramen ovale close at birth?
- Infant takes breath (when born)
- Everything opens and pulmonary vascular resistance
decreases - Pressure in right atrial pressure drops compared to left
- Higher LA pressure forces septum primum against
septum secundum and they fuse - Fossa ovalis remains
What causes a patent foramen ovale? is this usually treated? what complications can arise from this down the road?
septum primum and septum secundum fail to fuse at birth
no, but later on thromboemboli that enter atrial circulation can go from RA to LA then to brain
By what 3 ways can an atrial septal defect occur? how is this different from a patent forament ovale?
- failure of development of septum secundum
- excessive absorption of septum primum
- patent foramen primum
in this septa fail to develop in PDA the are there but fail to fuse
What do the septum primum and secundum arise from?
atrial wall and AV cushion
How do the developing ventricles gain access to the AV canal?
truncus arteriosis shifts right
cardiac cushion cells shift left
this shifts the right AV canal over
What is a double outlet right ventricle? how does this occur? symptoms? will this person have a VSD?
insufficent shifting of the truncus arteriosis
both aorta and pulmonary artery are in right ventricle
yes to VSD
sx: cyanosis, breathlessness
How is the outflow tract become the aorta and pulmonary trunk?
- NCC migrate to truncus arteriosus (undivided outflow
tract) and conus cordis, and combine with conotruncal endocardial cushion cells - Transform into mesenchyme that make two conotruncal ridges
- These two ridges grow towards each other and zip and
spiral - Aortopulmonary septum made and fuses with interventricular septum
- Eventually becomes ascending aorta and pulmonary
trunk
What are the three major tissue structures needed to separate the left and right ventricle? where do they come from
- muscular interventriclar septum from outgrowth
- aorticopulmonary septum rotates and fuses with muscular interventricular septum to form membranous part
- endocardial cushion cells contribute to membranous part of IVS
What is usually the cause of the major outflow tract defects? what is associated with all of them?
Defects in migration of neural crest cells, a VSD
What is persistent truncus arteriousus? cause? VSD?
failure of aorta and pulmonary trunk to fully divide
failure of NCC, has a VSD
What occurs in transposition of great vessels? cause? what do they need in order to survive?
great vessels switched, aorta in right ventricle, pulmonary trunk in left ventricle (2 closed loops, no oxygenated blood to system)
caused by shitty NCC and no spiraling
need a shunt to survive, VSD, patent ductus arteriousis or patent foramen ovale
What occurs in tetrolagy of fallot? (PROV) cayse?
pulmonary stenosis (yuge giveaway) RV hypertrophy (Cause of the pulmonary stenosis) overriding aorta (aorta over VSD) VSD
cause: shit NCC resulting in misplacement of the infundibular septum
What is pulmonary valvular atresia? signs? what do they need to survive?
no pulmonary semilunar valve
results in right ventricular hypoplasia
need PFO (so deoxygenated blood can get from right to left) , PDA (so deoxygenated blood can enter pulmonary circulation) to live
What is aortic valve atresia? signs? what do they need to survive?
no aortic valve, LV hypoplasia
need atrial septal defect (so oxygenated blood can go from left to right) and patent ductus arteriosis
(so blood can get into aorta)
what occurs in a bicuspid aortic valve?
2 leaflets instead of 3
LV hypertrophy cause it creates more resistance
What occurs in tricuspid atresia? what occurs? what do you need in order to survive?
no tricuspid valve
RV hypoplasia
need ASD, VSD or you die
What occurs in a hypoplastic left ventricle? what do you need to survive and why?
underdeveloped LV resulting in shit aortic semilunar and mitral valves resulting in shit ascending aorta
VSD
-so that oxygenated blood can move thr, and patent
foramen ovale or ASD,
-to get oxygenated blood from left to right side of heart
PDA
-so blood van go from pulmonary circulation to systemic
Which aortic arches contribute to nothing and just regress?
I, II, V
which aortic arches contribute the most?
III, IV, VI
What is the fate of the cervical segmental arteries?
vertebral a.
what is the fate of the left 7th intersegmental artery?
left subclavian a
what is the fate of the thoracic segmental arteries?
internal thoracic aa.
What is the fate of aortic arches I
regress
what is the fate of aortic arches II
regress
what is the fate of aortic arch III on the right
R: R common carotid, distal portion is internal carotid, proximal is external carotid
what is the fate of the left aortic arch III
becomes left common carotid, proximal is external distal is internal
What is the fate of left aortic arch IV?
ascending aorta, aortic arch, descending aorta
what is the fate of right aortic arch IV?
right subclavian a.
what is the fate of aortic arch V on both sides?
regress
what is the fate of aortic arch VI on the right?
proximal becomes right pulmonary a.
distal regresses
what is the fate of the aortic arch VI on the left?
proximal becomes left pulmonary a.
distal becomes ductus arteriosus
Why does the recurrent laryngeal nerve rise from the vagus nerve at two different levels in the adult?
on the right side the distal portion of VI regresses and it gets pulled up and caugh under the brachiocephalic trunk
on the left side it gets caught on the ligamentum arteriousus
what is the purpose of the ductus arteriousus?
to augment flow of oxygenated blood from pulmonary to systemic circulation in a fetus
how does the ductus arteriosus close after birth?
changes in O2 tension and blood flow decrease prostaglandin levels spurring smooth muscle contraction and it closes
what occurs in patent ductus arteriousus? what occurs to the heart as a result?
after birth, pulmonary circulation resistance drops dramatically
if this duct remains open, high pressure aortic circulation will take the path of least resistance into pulmonary circulation
left ventricular hypertrophy, pulmonary a congestion,
what is coarction of the aorta and which type is better and why?
thinning of aorta pre or post ductus arteriousus
post ductal is better because collateral circulation through the internal thoracic and intercostal arteries allows for profusion of blood to lower limbs
what causes abnormal origin of the right subclavian?
persistence of the right distal segment of dorsal aorta
regression of right proximal segment (IV)
R subclavian now wraps around espophagus, can cause dysphagia
what causes double aortic arches? what does this do
persistence of right distal segmant of dorsal aorta (VI)
entraps esophagus and trachea
what causes right aortic arch?
persistence of right distal segment
regression of left distal segment
what causes interrupted aortic arch? how does blood supply get to the descending aorta?
-abnormal regression of right and left arch IV
-ascending part is fine
descending part is toast
need patent ductus arteriosus to connect pulmonary trunk to descending aorta
How does double SVC occur?
no brachiocephalic anastomosis forms no brachiocephalic vein two SVC right is normal left drains to oblique sinus
how do you get a left sided SVC?
brachiocephalic anastomosis shunts blood right to left instead of left to right
connects to right atrium via oblique sinus
what does the truncus arteriosis become?
ascending aorta and pulmonary trunk
what does the bublus cordis become?
smooth part of outflow tract of ventricles
what does endocardial cushion become?
Atrial septum, membranous ventricular septum, AV and semilunar valves
what does the left horn of the sinus venosus become?
coronary sinus
what does the right horn of the sinus venosus become?
smooth part of right atrium (Sinus venarum)
what does the right common and anterior cardinal vein become?
SVC
What congenital abnormalities are associated with rubella?
PDA, pulmonary artery stenosis, septal defects
What congenital abnormalities are associated with downs?
AV septal defect (endocardial cushion( VSD, ASD
what congenital abnormalities are associated with turner syndrome
coarction of the aorta
What does the conus arteriosus form from?
Bulbus cordis
What is the most common ASD?
Septum secundum perforation.
How do you keep open a ductus arteriosus in hte case of heart defect
Ductus arteriosis usually closes within 1-2 hours of birth
Closes because of smooth muscle contraction of tunica media
Before birth there is low oxygen content = high prostaglandins –> which keep the smooth muscle of the artery relaxed and open. Flow of O2 at birth causes inhibition of prostaglandins → the smooth muscle to contarct.
