Embryology of the CVS 2

Question 1

What is the definition of Vasculogenesis and angiogenesis?

Answer 1

Vasculogenesis: New formation of a primitive vascular network

Angiogenesis: The growth of new vessels from pre-existing blood vessels

Question 2

What are the two first arteries seen?

Answer 2

•right and left primitive aortae

Question 3

What are the components of each primitive aorta?

Answer 3

Ventral aorta and dorsal aorta

Question 4

How is the aortic sac produced?

Answer 4

Fusion of ventral aorta

Question 5

Where do aortic branches arise from?

Answer 5

The aortic sac

Question 6

What are pharyngeal arteries?

Answer 6

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

Question 7

How are aortic branches formed?

Answer 7

•Develop from aortic branches and pharyngeal arch arteries

All are not present at the same time, they all terminate at the dorsal aorta

Question 8

Where do all the aortic arches terminate?

Answer 8

The dorsal aorta

Question 9

What is the fate of arches 1 and 2?

Answer 9

The 1st and 2nd arches disappear early, remnant of the 1st arch forms part of the maxillary artery (branch of external carotid a.)

Question 10

What is the fate of arch 3?

Answer 10

The 3rd aortic arch cis the start of the internal carotid a., and is therefore named the carotid arch

Question 11

What is the fate of arch 4?

Answer 11

The 4th right arch forms the right subclavian,

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

Question 12

What is the fate of the 5th aortic arch?

Answer 12

The 5th arch either never forms or forms incompletely and then regresses.

Question 13

What is the fate of the 6th aortic arch?

Answer 13

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

Question 14

Summary of the arches

Answer 14

Question 15

Why do most of the great artery anomalies arise?

Answer 15

As a result of persistence of aortic arches that normally should regress or regression of arches that normally shouldn’t.

Question 16

What is aberrant subclavian artery?

Answer 16

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

Question 17

What is double aortic arch?

Answer 17

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

Question 18

What is PDA?

Answer 18

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.

Question 19

What is coarctation of the aorta?

Answer 19

Congenital condiditon

Aorta is narrow usually in the area where the ducts arteriosis inserts

Question 20

What does coarctation mean?

Answer 20

Narrowing

Question 21

Where are coarctations most common?

Answer 21

In the aortic arch

Question 22

What are the three forms of embryonic circulation?

Answer 22

Vitelline

Umbilical

Cardinal

Question 23

What do the vitelline arteries supply in the embryo?

Answer 23

The yolk sac

Question 24

In an adult what are the vitelline arteries represented by?

Answer 24

Celiac artery - artery of the foregut

Superior mesenteric artery - artery of the midgut

Inferior mesenteric artery - artery of the hindgut

Question 25

What are the umbilical arteries before birth?

Answer 25

Paired branches of the dorsal aorta to placenta

Question 26

What happens to the proximal portion and the distal portion of the umbilical arteries before and after birth?

Answer 26

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

Question 27

What is the role of the vitelline veins?

Answer 27

Carries blood from the yolk sac to the sinus venosus

Question 28

What is the role of umbilical veins?

Answer 28

•Originate from chorionic villi of placenta carrying oxygenated blood to the embryo

Question 29

What is the function of the cardinal veins?

Answer 29

Drain the body of the embryo

Question 30

What do the viteline veins form?

Answer 30

Portal vein

Hepatocardiac (liver to heart) part of the inferior vena cava

Liver sinusoids

Superior mesenteric vein

Question 31

What is the fate of the umbilical veins?

Answer 31

• 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

Question 32

What is the function of the ductus venosus in the foetus?

Answer 32

Shunts blood from left umbilical vein directly into the inferior vena cava - allows ozygenated blood from the placenta to bypass the liver

Question 33

What is the function of the cardinal veins?

Answer 33

Carry blood from the head and the lower body into the heart.

Ancestors of all intraembryonic vasculature

Question 34

What does the cardinal vein system consist of?

Answer 34

• anterior, posterior & common cardinal veins draining to sinus venosus

Question 35

What do the cardinal veins form?

Answer 35

•Form vena caval (SVC and IVC) system by anastomosis among the veins

Question 36

What are the venous system abnormalities?

Answer 36

Question 37

When does the lymphatic system develop?

Answer 37

At the end of the sixth week around main veins

Question 38

What lymphatic components have been developed at the end of the embryonic period?

Answer 38

Six primary lymph sacs will be developed

•Lymphatic vessels will join the lymph sacs later

Question 39

What is the normal circulatory transition at birth?

Answer 39

Placental circulation to pulmonary circulation

Question 40

How does the ductus venosus change on transition to neonate?

Answer 40

Shunts left umbilical vein blood flow directly to IVC: allows oxygenated blood from the placenta to bypass the liver.

Obliterates and forms ligamentum venosum

Question 41

How does the oval foramen change on transition to neonate?

Answer 41

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.

Question 42

How does the ductus arteriosus change on birth?

Answer 42

Originally: Allows blood that still escapes the right ventricle to bypass the lungs.

Ductus is obliterated and becomes the ligamentum arteriosum

Question 43

What is the path of the deoxygenated blood from the aorta?

Answer 43

Question 44

What happens to the umbilibal vein?

Answer 44

Becomes solid ligamentum teres

Question 45

Which gender is patent ductus arteriosus more common in?

Answer 45

More frequent in females

Question 46

What is patent ductus arteriosus associated with?

Answer 46

Maternal rubella infection

Question 47

What causes patent ductus arteriosus?

Answer 47

Failure of muscular wall to contract, respiratory distress syndrome (low O2) and lack of surfactant in the lungs.

Question 48

In 90% of cases where does coarctation occur?

Answer 48

Opposite the ductus arteriosus

Question 49

What are the main theories of cause of coarctication?

Answer 49

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