Embryology of the CVS 2 ND Flashcards
What are the two ways the blood vessels develop?
Vasculogenesis
- defined as the new formation of a primitive vascular network
Angiogenesis
- defined as the growth of new vessels from pre-existing blood vessels
The aortic sac is an extension of which part of the primitive heart tube?
Truncus arteriosis
How does the aortic sac form?
Fusion of the ventral part of the left and right aortae
when the two heart tubes fuse together to form the single heart tube
What are the first arteries to appear in the embryo?
Left and right primitive aortae
Describe the appearance of the primitive aortae
Have a ventral part that arches over into a dorsal part
What happens after the fusion of the aortae to form the aortic sac?
Aortic branches arise from the aortic sac
6 on either side
When do the pharyngeal arches develop?
4th & 5th week
After formation of the pharyngeal arches, what happens involving the aortic branches?
Each pharyngeal arch has its own nerve and artery
The pharyngeal arch arteries join with the aortic branches
This forms the 6 AORTIC ARCHES on each side, which connect the dorsal aorta to the ventral aorta on either side
However, they are not all present at the same time
What is the fate of the 1st aortic arches?
It disappears
A remnant of the 1st arch forms part of the maxillary artery (branch of external carotid a.)
What is the fate of the 2nd aortic arches?
It disappears
What is the fate of the 3rd aortic arches?
Internal carotid artery
hence it is sometimes called the carotid arch
What is the fate of the 4th aortic arches?
Right 4th = Right subclavian
Left 4th = Aortic arch
What is the fate of the 5th aortic arches?
5th arch either never forms or forms incompletely and then regresses
What is the fate of the 6th aortic arches?
The proximal part of the sixth right arch persists as the proximal part of the right pulmonary artery while the distal section degenerates
The sixth left arch gives off the left pulmonary artery and forms the ductus arteriosus
What is the ductus arteriosus and what happens to it?
Little tube thing connecting pulmonary artery to aorta
It turns into ligamentum arteriosum between 1-3 months after birth
What generally causes abnormalities in the great arteries?
Persistence of aortic arches that normally should regress
or
Regression of arches that normally shouldn’t.
Give examples of congenital abnormalities in the great arteries
Aberrant subclavian artery
Double aortic arch
Patent ductus arteriosus(PDA)
Coarctation of the Aorta
What is an aberrant subclavian artery?
rightsubclavian arteryhas an abnormal origin on the left side
To supply blood to the right arm, this forces the right subclavian artery to cross the midline behind thetrachea and oesophagus
may constrict these organs, although usually with no clinical symptoms
What is a double aortic arch?
Aorta with two arches, with the trachea and oesophagus passing through the hole in between the two arches
Difficulty breathing and swallowing
What is Patent ductus arteriosus (PDA)?
Ductus arteriosusfails to close afterbirth
Early symptoms are uncommon, but in the first year of life include increased ‘work of breathing’ and poor weight gain
An uncorrected PDA may lead to congestiveheart failurewith increasing age.
What is Coartication of the aorta?
Congenital condition wherein theaortais narrow
Usually in the area where the ductus arteriosus (ligamentum arteriosum after regression) inserts
Can be proximal to ductus arteriosus (preductal) or distal to it (postductal
What are the 3 main circulations in an emrbyo
Vitelline = yolk sac
Umbilical = placental
Cardinal = rest of body
What is the fate of the vitelline arteries?
In adult are represented by arteries to the foregut, midgut & hindgut
What is the structure of the umbillical arteries before birth ?
Paired branches of the dorsal aorta to placenta
What is the fate of the umbillical arteries?
Proximal portion persists as internal iliac and superior vesical branches to urinary bladder
Where do all embryonic veins enter?
Sinus venosus
Which venous system in the embryo is the largest?
Cardinal venous system
Describe the different cardinal veins
System consists of – anterior, posterior & common cardinal veins draining to sinus venosus
What is the fate of the cardinal venous system?
Form vena cava (SVC and IVC) system by anastomosis among the veins
Give some examples of abnormalities with development of the venous system
Double IVC
Absence of IVC
Left SVC
Double SVC
How/when does the lymphatic system develop?
Develops at the end of sixth week around main veins
Six primary lymph sacs develops at the end of embryonic period
Lymphatic vessels will join the lymph sacs later
When a baby is born, it changes from maternal breathing to independent breathing
Several parts of the CVS are important in this transition
What are they?
Ductus venosus (shunts left umbilical vein blood flow directly to IVC: allows oxygenated blood from the placenta to bypass the liver).
Oval foramen (allows blood to enter the leftatriumfrom the right atrium: allows blood to bypass the lungs).
Ductus arteriosus (allows blood that still escapes to the right ventricle to bypass thelungs).
