Embryology of CVS 2

Question 1

Describe vascular development

Answer 1

-2 processes: vasculogenesis + angiogenesis
Vasculogenesis; new formation of a primitive vascular network
Angiogenesis; growth of new vessels from pre-exisdting blood vessels

Question 2

Formation of aortic sac

Answer 2

• extension of truncus arteriosus of primitive heart tube
• each primitive aorta has a ventral part ( ventral aorta) and a dorsal part ( dorsal aorta)
• after fusion of two endothelial tubes the two ventral aortae partially duse to form the aortic sac
• aortic branches arise from aortic sac

Question 3

Development of pharyngeal arch arteries + aortic branches

Answer 3

• pharyngeal arches(future neck) develop during 4th/5th week
• each arch recieves its own nerve + artery => pharyngeal arteries
• pharyngeal arteries join with aortic branches = aortic arches
• 6 aortic arches are formed on each side, all in communication with dorsal aortae
• arches terminate in the dorsal aorta

Question 4

Fate of arches 1 + 2

Answer 4

• disappear early, but remnant of the 1st arch forms part of the maxillary artery ( branch of external carotid artery)

Question 5

Fate of arches of 3

Answer 5

-commencement of internal carotid artery= carotid arch

Question 6

Fate of arch 4

Answer 6

• 4th right arch forms right subclavian

- 4th left arch constitutes the distal part of the aortic arch

Question 7

Fate of arch 5

Answer 7

• the arch either never forms/forms incompletely and regresses

Question 8

Fate of arch 6

Answer 8

• the proximal part of the 6th right arch persists as the proximal part of the right pul. artery
• 6th left arch gives off the left pul. artery + forms the ductus arteriosus(connection between LPA+aorta) ; within 1-3 months the ductus is obliberated and becomes the ligamentum artieriosum

Question 9

Causes of defects of the great artieries

Answer 9

-as a result of persistence of aortic arches that should regress/regression of arches that normally shouldn’t

Question 10

What is aberrant subclavian artery?

Answer 10

• Righ subclavian artery supposed to arise from trunk of brachiocephalic artery but instead arises from left aortic arch.
• to supply to the right arm, right subclavian artery to cross the midline behind the trachea and oesophagus which may constrict these organs
• asymptomatic

Question 11

How does a double aortic arch occur?

Answer 11

occurs with the non-regression(not be there) of the right aortic arch ; an abnormal right aortic arch in addition o the left aortic arch - forming a vasular ring around the trachea + oesophogus ehich causes difficulty breathing/swallowing

Question 12

Patent ductus arteriosus ( PDA) - What is it, symptoms + causes

Answer 12

• common in females
• associated with maternal rubella infection ( early pregnancy)
• cause ; failure of SM wall(DA) to contract, respiratory distress syndrome ( low O2) + lack of surfactant in the lungs
• condition where the ductus arterorisus fails to close after birth. Symptoms include increased work of breathing/poor weight gain. Unresolved leads to congestive HF
• symptoms include cyanosis

Question 13

What is Coarctation(constriction) of the aorta

Answer 13

• aorta becomes narrow in the area where ductus arteriosus ( ligamentum arteriosum after regression) inserts.
• Can be proximal to ductus arteriosus ( preductal or distal to it (postductal) or opposite(most common)

Question 14

Possible causes of coarctation of aorta

Answer 14

• incoporation of muscle tissue of DA into arch of aorta ( during development)
• when DA contracts after birth, part of arch also constricts
• Genetic/endivronmental factors

Question 15

Fate of vitelline arteries

Answer 15

• vitelline arteries supply yolk sac in embryo

- in adult, represented by arteries to the foregut, midgut, hindgut

Question 16

Fate of umbilical arteries

Answer 16

Before birth
-paired branches of the dorsal aorta to placenta

After birth
-proximal portion presists as internal iliac + superior vesical branches to urinary bladder

Question 17

Embryonic venous system

Answer 17

Vitelline veins - carry blood from yolk sac to the sinus venosus

Umbillical veins - originate from placenta carrying oxygenated blood to the embryo

Cardinal veins - draining the body of the embryo

Question 18

Fate of the cardinal veins

Answer 18

• main venous drainage system of the embryo

- forms vena caval ( SVC and IVC) system by anastomosis among the veins

Question 19

Development of lymphatic system

Answer 19

• develops arond 6 main veins
• 6 primary lymph sacs develops at the end of the embryonic period
• lymphatic vessels will join the lymph sacs later

Question 20

Foetal circulation shunts

Answer 20

1. Ductus venosus ( shunts left u.vein blood flow directly to IVC: allows oxygenated blood from the placenta to bypass the liver)
2. Oval foramen ( allows blood to enter the left atrium from the right atrium: allows blood to bypass the lungs)
3. Ductus arteriosus ( allows blood that still escaped to the right ventricle to bypass the lungs)

Question 21

Neonatal circulation changes after the birth

Answer 21

Closure of shutns and umbilical arteries

Ductus venosus becomes the ligamentum venosum of the liver

Oval forament closes after birth by tissue proliferation and adhesion of septal structueres > fosssa ovalis

Ductus arteriosus obliberated to form ligamentum arteriosum

Umbillical arteries ligamentous - medial umbillical ligamanets