Embryology of the CVS 2 Flashcards
What is the definition of Vasculogenesis and angiogenesis?
Vasculogenesis: New formation of a primitive vascular network
Angiogenesis: The growth of new vessels from pre-existing blood vessels
What are the two first arteries seen?
•right and left primitive aortae
What are the components of each primitive aorta?
Ventral aorta and dorsal aorta
How is the aortic sac produced?
Fusion of ventral aorta
Where do aortic branches arise from?
The aortic sac
What are pharyngeal arteries?
Supply pharyngeal arches
Communicate with aortic branches which are now called aortic arches
Each pharyngeal arch also has its own nerve supply
Pharyngeal arches are the future neck which develop during weeks 4 and 5
How are aortic branches formed?
•Develop from aortic branches and pharyngeal arch arteries
All are not present at the same time, they all terminate at the dorsal aorta
Where do all the aortic arches terminate?
The dorsal aorta
What is the fate of arches 1 and 2?
The 1st and 2nd arches disappear early, remnant of the 1st arch forms part of the maxillary artery (branch of external carotid a.)
What is the fate of arch 3?
The 3rd aortic arch cis the start of the internal carotid a., and is therefore named the carotid arch
What is the fate of arch 4?
The 4th right arch forms the right subclavian,
The 4th left arch constitutes the distal part of aortic arch
What is the fate of the 5th aortic arch?
The 5th arch either never forms or forms incompletely and then regresses.
What is the fate of the 6th aortic arch?
The proximal part of the 6th right arch persists as the proximal part of the right pulmonary artery
The 6th left arch gives off the left pulmonary a. and forms the ductus arteriosus; within 1–3 months, the ductus is obliterated and becomes the ligamentum arteriosum
Summary of the arches
Why do most of the great artery anomalies arise?
As a result of persistence of aortic arches that normally should regress or regression of arches that normally shouldn’t.
What is aberrant subclavian artery?
Right subclavian vein has an abnormal origin on the left side, to supply the arm it must cross the midline behind the trachea and oesophagus which may constrict these organs
What is double aortic arch?
Development of right aortic arch as well as left aortic arch, forming a vascular ring around the trachea and oesophagus whuch usually causes difficulty breathing and swallowing
What is PDA?
Patent ductus arteriosus: Fails to close after birth (would normally form ligamentum arteriosis)
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 congestive heart failure with increasing age.
What is coarctation of the aorta?
Congenital condiditon
Aorta is narrow usually in the area where the ducts arteriosis inserts
What does coarctation mean?
Narrowing
Where are coarctations most common?
In the aortic arch
What are the three forms of embryonic circulation?
Vitelline
Umbilical
Cardinal
What do the vitelline arteries supply in the embryo?
The yolk sac
In an adult what are the vitelline arteries represented by?
Celiac artery - artery of the foregut
Superior mesenteric artery - artery of the midgut
Inferior mesenteric artery - artery of the hindgut
What are the umbilical arteries before birth?
Paired branches of the dorsal aorta to placenta
What happens to the proximal portion and the distal portion of the umbilical arteries before and after birth?
Proximal portion - Persists as internal iliac and superior vesical branches (to urinary bladder)
Distal portion - degenerates to form obliterated umbilical arteries & forms medial umbilical ligaments
What is the role of the vitelline veins?
Carries blood from the yolk sac to the sinus venosus
What is the role of umbilical veins?
•Originate from chorionic villi of placenta carrying oxygenated blood to the embryo
What is the function of the cardinal veins?
Drain the body of the embryo
What do the viteline veins form?
Portal vein
Hepatocardiac (liver to heart) part of the inferior vena cava
Liver sinusoids
Superior mesenteric vein
What is the fate of the umbilical veins?
- Right Umbilical vein degenerates completely
- Left umbilical vein obliterates and forms ligamentum teres (=round ligament) of adult liver (teres = round)
- Ductus venosus obliterates and forms ligamentum venosum
What is the function of the ductus venosus in the foetus?
Shunts blood from left umbilical vein directly into the inferior vena cava - allows ozygenated blood from the placenta to bypass the liver
What is the function of the cardinal veins?
Carry blood from the head and the lower body into the heart.
Ancestors of all intraembryonic vasculature
What does the cardinal vein system consist of?
• anterior, posterior & common cardinal veins draining to sinus venosus
What do the cardinal veins form?
•Form vena caval (SVC and IVC) system by anastomosis among the veins
What are the venous system abnormalities?
When does the lymphatic system develop?
At the end of the sixth week around main veins
What lymphatic components have been developed at the end of the embryonic period?
Six primary lymph sacs will be developed
•Lymphatic vessels will join the lymph sacs later
What is the normal circulatory transition at birth?
Placental circulation to pulmonary circulation
How does the ductus venosus change on transition to neonate?
Shunts left umbilical vein blood flow directly to IVC: allows oxygenated blood from the placenta to bypass the liver.
Obliterates and forms ligamentum venosum
How does the oval foramen change on transition to neonate?
Allows blood to enter the left atrium from the right atrium: allows blood to bypass the lungs.
Normally this opening closes at birth. When the lungs become functional at birth, the pulmonary pressure decreases and the left atrial pressure exceeds that of the right. This forces the septum primum against the septum secundum, functionally closing the foramen ovale. In time the septa eventually fuse, leaving a remnant of the foramen ovale, the fossa ovalis.
How does the ductus arteriosus change on birth?
Originally: Allows blood that still escapes the right ventricle to bypass the lungs.
Ductus is obliterated and becomes the ligamentum arteriosum
What is the path of the deoxygenated blood from the aorta?
What happens to the umbilibal vein?
Becomes solid ligamentum teres
Which gender is patent ductus arteriosus more common in?
More frequent in females
What is patent ductus arteriosus associated with?
Maternal rubella infection
What causes patent ductus arteriosus?
Failure of muscular wall to contract, respiratory distress syndrome (low O2) and lack of surfactant in the lungs.
In 90% of cases where does coarctation occur?
Opposite the ductus arteriosus
What are the main theories of cause of coarctication?
Incorporation of muscle tissue of descending aorta into arch of aorta (during development). When descending aorta contracts after birth, part of the arch also constricts.
Genetic / environmental factors
