Development of the vascular system Flashcards
What are dorsal aortas?
paired and run the length of the embryo
Where does the arterial tree originate?
from the aortic sac emerging from the primordial heart
What does the upper left dorsal aorta become?
the descending thoracic aorta
What happens to the right dorsal aorta?
regresses
What do the dorsal aortas fuse caudally to form?
lower thoracic and abdominal aorta
What do the dorsal aortas terminate caudally as?
the median sacral artery
Where do pharyngeal arch arteries arise?
arise from cranial portion of the dorsal aortas
Where doe the intersegmental arteries arise from?
arise from caudal portion of the dorsal arteries
Where do intersegmental arteries pass?
between somites and supply their derivatives
Intersegment arteries merge where to form what?
merge in the cervical region to form vertebral arteries
- lose their connections to the dorsal aortas
What do intersegmental arteries persist in the thoracic region?
as posterior intercostal arteries
What do intersegmental arteries persist as in the lumbar region?
as lumbar arteries
The fifth lumbar intersegmental arteries become what?
become the common iliac arteries
Where do the intersegmental arteries merge and what do they form?
merge in the sacral region to form lateral sacral arteries
Where do vitelline arteries branch and pass?
branch from dorsal aorta and pass to the umbilical vesicle
What does the vitelline artery persist as in the foregut?
the celiac trunk
What does the vitelline artery persist as in the midgut?
superior mesenteric artery
What does the vitelline artery persist as in the hindgut?
inferior mesenteric artery
Where do the umbilical arteries pass through?
pass through the connecting stalk to the chorion
What do the umbilical arteries carry?
deoxygenated blood back to the placenta
What do proximal segments on umbilical arteries persist as?
internal iliac arteries and superior vesical arteries
What happens to the umbilical arteries in distal segments?
obliterate to become the medial umbilical ligaments
How many paired veins are present in week 4?
3 pairs
What are the 3 pairs of veins present in week 4
- vitelline veins
- umbilical veins
- common cardinal veins
What do the vitelline veins contain?
contain poorly oxygenated blood from umbilical vesicle
Between what does the vitelline veins follow?
follow the omphaloenteric duct (yolk sac) into embryo
What do the vitelline veins drain to?
the sinus venosus in the developing heart
What happens to the left vitelline vein?
will regress
What happens to the right vitelline vein?
forms:
- most of the hepatic portal venous system - part of the inferior vena cava
What do umbilical veins contain?
contain highly oxygenated blood from the chorion
Where do umbilical veins drain to originally?
originally drain to sinus venosus
Where do umbilical veins drain to later on?
lose connection to the heart and drain to liver as liver enlarges
What happens to the right umbilical and cranial part of left umbilical vein?
degenerate
What does the left umbilical vein persist as?
- where does it carry blood from?
persists as the umbilical vein
- carries oxygenated blood from placenta to embryo
Where does the ductus venoses develop?
in the liver
Where does the ductus venosus shunt blood?
shunts blood from umbilical vein to inferior vena cava
What is the the importance of the ductus venosus?
allows most oxygenated blood to bypass liver sinusoids and go directly to heart
What do the common cardinal veins contain?
contain poorly oxygenated blood from body of embryo
What does the common cardinal veins receive?
receive the anterior and posterior cardinal veins on each side
Where does the common cardinal veins drain?
drains to sinus venosus
What do the anterior cardinal veins drain?
drain cranial parts of the embryo
What happens in week 8 to the 2 cardinal veins?
an anastomosis forms between the 2 anterior cardinal veins
What forms from the anastomoses of the anterior cardinal veins?
left brachiocephalic vein
- left anterior and left common cardinal veins degenerate
The right anterior and right common cardinal veins form what?
superior vena cava
What do posterior cardinal veins drain?
drain caudal parts of the embryo
What do the posterior cardinal veins develop as?
develop as the vessels of the mesonephric kidneys
- largely disappear with the degeneration of these kidneys - essentially replaced by subcardinal and supracardinal veins
What do posterior cardinal veins form in adults?
arch of azygous vein and common iliac veins
What develops first in posterior cardinal veins?
subcardinal veins
What do subcardinal veins form part of?
form part of IVC, left renal vein, bith suprarenal veins ad both gonadal veins
What develops later in posterior cardinal veins?
supracardinal veins
Where do supracardinal veins separate?
separate craniocaudally in the area of the kidneys
What do supracardinal veins forrm?
form azygous vein and hemiazygouz vein superior the separation in the area of the kidneys
Inferior to the separation in the area of the kidneys, what does the right supracardinal vein become? left supracardinal vein?
- right = IVC
- left = degenerates
The hepatic segment of inferior vena cava is derived from what?
right vitelline vein
The prerenal segment of the inferior vena cava is derived from what?
right subcardinal vein
The subcardinal-supracardinal anastomoses makes what segment of the inferior vena cava?
renal segment
The right supracardinal vein forms what inferior vena cava segment?
postrenal segment
Where might the IVC be discontinuous in in IVC anomalies?
in abdomen or in live ( both are uncommon)
What is the venous return in a discontinuous IVC?
- diverts venous return through azygous system
- hepatic veins may drain directly to right atrium
What causes a double SVC?
due to a persistent left anterior cardinal vein and common cardinal vein
What does a double SVC drain?
usually drains to right atrium via coronary sinus
What causes a left SVC?
due to a persistent left anterior cardinal vein and degeneration of right
Where does a left SVC drain?
usually drains to right atrium via coronary sinus
What does the umbilical vein carry?
carries oxygen rich and nutrient rich blood from placenta
What does the ductus venosus allow?
allows approximately half of this blood to bypass the liver into the IVC
Where does the other half of the blood from ductus venosus flow through?
through liver sinusoids and enters IVC via hepatic veins
What does the IVC contain in fetal circulation?
- nutrient rich and oxygen rich blood contributed indirectly by umbilical vein
- typical venous return from abdomen, pelvic and lower extremities
Through what does most blood in IVC pass from right atrium to left atrium?
foramen ovale
Whats the importance of having a small amount of blood to pass to the right ventricle and then through the pulmonary trunk?
allows right ventricle to develop while having some work to do
Which ventricle is thicker during fetal development?
the wall of the right ventricle
- due to pulmonary vascular resistance in utero
What is the function of the 10% of blood in the pulmonary trunk which goes to the lungs?
to supply oxygen to the lungs
What does the 90% of blood in the pulmonary trunk passing through the ductus arteriosus supply?
shunts blood into the descending aorta for distribution to the fetus
What is the circulation pattern in the fetus from left atrium?
left atrium => left ventricle => ascending aorta
What is of high value to the fetus from the placenta?
blood to heart, head, neck and upper extremities
What adds blood to the descending aorta?
ductus arteriosus
What is of medium value to the fetus from the placenta?
blood to abdomen, pelvis, lower extremities
In neonatal circulation, what happens to the umbilical vein?
remains patent for some time, months
What does the umbilical vein become in neonatal circulation?
becomes the ligamentum teres (or round ligament of the liver)
What does the ductus venosus become? why?
becomes the ligamentum venosum
- closes as no blood is flowing through the umbilical vein - blood pressure in IVC and right atrium decreases because of this change
What happens when lungs start to function?
- pulmonary vascular resistance decreases
- pulmonary blood flow increases
- BP in L atrium increases above R atrium
- Increased L atrial pressure closes foramen ovale
- septum primum and secundum fuses ~3months
- adult remnant = fossa ovalis
What happens to the lungs with reduced pulmonary vascular resistance?
right ventricle atrophies
What happens to the left ventricle with increased systemic vascular resistance?
hypertrophies
What happens to blood flow in initially in the ductus arteriosus in noenatal circulation? after 96 hours of birth?
- blood flow initially reverses
- ductus arteriosus closes completely within 96hrs
What does the ductus arteriosum become?
ligamentum arteriosum
What are the umbilical arteries visible as in neonatal circulation?
visible as the obliterated umbilical arteries (or medial umbilical ligaments)
- located in medial umbilical folds of the adults
What is a patent ductus arteriosus a result of?
associated with maternal rubella infection during pregnancy
What is associated with a patent ductus arteriosus?
associated with hypoxia and low birth weight
- aortic blood shunts to pulmonary trunk
What is Aortic coarctation?
constriction of the aorta along a segment of varying length; distal to the origin of left subclavian artery
What is postductal coarctation?
constriction occurs just distal to the ductus arteriosus
- permits development of a collateral circulation during fetal development to supply inferior regions of body
What is a preductal coarctation?
constriction occurs just proximal to thee ductus arteriosus
- fetal circulation to inferior regions is dependent on ductus arteriosus
