Embryology 2 Flashcards
What is vasculogenesis?
New formation of a primitive vascular network
What is angiogenesis?
Growth of new vessels from pre-existing blood vessels
How is the aortic sac formed?
2 primitive aorta with endothelial heart tube
- > Endothelial heart tubes fuse to form a single primitive heart tube
- > 2 ventral sections of primitive aorta fuse to form the aortic sac
From where do aortic branches arise?
The Aortic sac, they connect to it on one side and the remaining dorsal section of the aorta at the other.
What embryonic structure becomes the neck?
Pharyngeal arches
What do we call the blood and nerve supply of the pharyngeal arches?
Pharyngeal arteries & nerves
What becomes of the 1st aortic arch?
It dissapears early on but its remnants form part of the maxillary artery, a branch of the external carotid artery
What happens to the 2nd aortic arch?
It dissapears entirely early on
Whats the fate of the 3rd aortic arch?
The start of the internal carotid artery, therefore its known as the carotid arch
What happens to the 4th aortic arch?
The left one becomes the distal part of the aortic arch
The right one forms the right subclavian
What becomes of the 5th aortic arch?
It never forms or it does but incompletely and regresses
What happens to the 6th right aortic arch?
It becomes the proximal part of the right pulmonary artery
What happens to the 6th left aortic arch?
It gives off the left pulmonary artery
Then forms the Ductus Arteriosus connecting aorta and pulmonary trunk, to help bypass the lungs
What is the origin and fate of the ductus arteriosus?
The Ductus Arteriosus arises from the 6th left aortic arch.
Within 3 months its obliterated & becomes the ligamentum arteriosum.
What condition arises from regression of the 4th right aortic arch and the right dorsal aorta?
An aberrant subclavian artery, the right subclavian has its origin on the left side on the aortic arch instead of the right.
The right subclavian passes behind the oesophagus & trachea which can constrict them
When does a double aortic arch occur?
When a second aortic arch forms, on the right. forming a vascular ring round the trachea + oesophagus which can cause breathing and swallowing problems
What are the signs of PDA?
Increased work of breathing & poor weight gain in the first year
Congestive heart failure with increasing age
What is coarctation of the aorta?
Narrowing of the aorta, most often in the aortic arch
What are the 2 types of coarctation of the aorta?
Preductal, which occurs proximal to the ductus arteriosus
Postductal which occurs distal to the ductus arteriosus
The vitelline arteries supply the yolk sac, but what do they become in adults?
Celiac Artery - Artery of the Foregut
Superior Mesenteric a. - Artery of midgut
Inferior Mesenteric a. - Artery of hindgut
Where do the umbilical arteries originate/supply?
As paired branches of the doral aorta/
They supply the placenta
What happens to the proximal portion of the umbilical arteries after birth?
They persist as the internal iliac and superior vesical branches (supplies urinary bladder)
What happens to the distal portion of the umbilical arteries after birth?
They are obliterated and form medial umbilical ligaments
What are the main veins of the embryo and their function?
The vitelline veins - Carry blood from yolk sac to sinus venosus
Umbilical Veins = carry oxygenated blood from placenta to embryo
Cardinal veins = drain the body of the embryo
What is the adult fate of the vitelline veins
They become the portal vein between gut and liver.
The hepatocardiac section of the IVC
Liver Sinusoids
Superior mesenteric vein
What are sinusoids?
small irregular blood vessels in certain organs
What becomes of the right umbilical vein?
It degenerates completely before adulthood
What happens to the left umbilical vein?
It obliterates and becomes the ligamentum teres hepatus or round ligament of the liver.
What is the ductus venosus?
A section of umbilical vein shunting blood from the left umbilical vein to the IVC so oxygenated blood from the placenta bypasses the liver.
What happens to the ductus venosus in adults?
It obliterates and forms the ligamentum venosum
What are the cardinal veins and where do they drain to?
Anterior, Posterior and Common.
All drain to the sinus venosus
What do the cardinal veins become in an adult?
The SVC & IVC.
Name some venous congenital abnormalities?
A double IVC below the kidneys
A complete lack of IVC
The SVC on the left looping under the pulmonary veins and left atrium to reach the right atirum instead of the right.
A Double SVC, one normal and one left (as above)
What three things change at birth when the liver and lungs begin functioning properly?
The ductus venosus (helps blood bypass liver) - Becomes ligamentum venosum Oval foramen (allows blood to bypass pulmonary circulation) - Becomes Fossa Ovalis Ductus Arteriosus (passes any blood that does get to the pulmonary trunk on to the aorta) = Becomes ligamentum arteriosus
What are the steps of foetal circulation?
Aorta -> Descending Aorta -> Abdominal Aorta -> Common Iliac Artery -> Umbilical arteries -> Placenta -> Umbilical Vein
What is commonly associated with PDA?
A maternal rubella infection
What causes PDA?
- Failure of muscular wall to contract
What happens during PDA?
Respiratory distress syndrome (low O2)
What is the main theory for the cause of aortic coarctation?
The Ductus Arteriosus muscle cells are incorporated into the aortic arch and when they contract after birth they constrict the aorta.
