Embryology

Question 1

1st aortic arch

Answer 1

small part of maxillary

Question 2

2nd aortic arch

Answer 2

artery to stapedius (small muscle located inside the middle ear)

Question 3

3rd pair of aortic arches

Answer 3

Common carotid arteries

Question 4

Right 4th aortic arch

Answer 4

Proximal part of right subclavian artery

Question 5

Left 4th aortic arch

Answer 5

Arch of aorta

Question 6

Right 6th aortic arch

Answer 6

Right pulmonary artery

Question 7

Left 6th aortic arch

Answer 7

Left pulmonary artery and ductus arteriosus

Question 8

Right 7th segmental arch

Answer 8

Right subclavian artery

Question 9

Left 7th segmental arch

Answer 9

Left subclavian artery

Question 10

Right dorsal aorta

Answer 10

Regresses except for a portion that forms middle of the right subclavian artery

Question 11

Left dorsal aorta

Answer 11

Descending thoracic aorta

Question 12

Aortic sac

Answer 12

Ascending aorta and brachiocephalic artery

Question 13

Gastrulation

Answer 13

mass movement and invagination of the blastula to form 3 layer- ectoderm, mesoderm and endoderm

Question 14

Which cell layer(s) make CVR system

Answer 14

most of cardiovascular system is derived from cells which were situated in the mesoderm (blood, heart, smooth muscle and endothelium)
• Some contribution from cardiac neural crest cells from the ectoderm (contributes to cardiac outflow and coronary arteries)

Question 15

First heart field

Answer 15

Future left ventricle

Question 16

Second heart field

Answer 16

outflow tract, future right ventricle and atria

Question 17

When does development of cardiovascular system begin

Answer 17

Week 3

Question 18

Stages of embryology of heart - formation of primitive heart tube

Answer 18

1. Mesoderm cells travel through primitive streak to embryo’s head and form horseshoe-shaped area with 2 limbs (ie primary heart field)- cardiogenic region
2. day 19-21: lateral folding: embryo folds into cylindrical shape as lateral borders meet at midline- 2 endocardial tubes fuse, forming primitive heart tube
3. Craniocaudal folding positions in thoracic region
4. Heart tube grows and develops bulges

Question 19

Partition of the heart tube

Answer 19

• sinus venosus: left and right sinus horn bring in blood (superior vena cava) and part of right atrium
• Primitive atrium and primitive ventricle separated by atrioventricular sulcus
• Primitive atrium → left and right atria
• Primitive ventricle → left ventricle
• Bulbus cordis → right ventricle and outflow tracts for both ventricles (aorta and pulmonary trunk)

Question 20

What happens day 22

Answer 20

Heart begins to beat

Question 21

Looping of the heart

Answer 21

heart tube folds into C shape
• tube lengthens
• Walls thicken
• Sections move toward appropriate locations to continue development
• Bulbis cordis moves inferiorly, anteriorly and to the embryo’s right
• Primitive ventricle moves to embryo’s left side
• primitive atrium and sinus venosus move superiorly and posteriorly
• Sinus venosus is posterior to primitive atrium
• During development, the node secretes nodal, which circulates to the left due to ciliary movement
• A cascade of transcription factors (e.g. Lefty, Pitx2, Fog-1) transduce looping

Question 22

How does the Bulbus cordis move

Answer 22

inferiorly, anteriorly and to the embryo’s right

Question 23

How does the primitive ventricle move

Answer 23

moves to embryo’s left side

Question 24

Where does the primitive atrium and sinus venosus move to

Answer 24

move superiorly and posteriorly

Sinus venosus is posterior to primitive atrium

Question 25

Cardiac septation

Answer 25

atrium and ventricle connected by atrioventricular canal • Blood first enter the atrium passes through the atrioventricular canal and into the ventricle. Exits the heart the the Truncus arteriosus • Masses of tissue called endocardial cushions grow from the sides of the atrioventricular canal to partition it into 2 separate openings • As the endocardial cushions grow together, the atrioventricular canal also is repositioned to the right of the heart • The superior and inferior endocardial cushions fuse, forming 2 separate openings- the left and right atrioventricular canals • endocardial cells proliferate on ventricular side of each canal- form leaflets of mitral and tricuspid valves • Canals now divided into atria and ventricles

Question 26

What does the sinus venosus become

Answer 26

left and right sinus horn bring in blood (superior vena cava) and part of right atrium

Question 27

What does the primitive atrium become

Answer 27

Left and right atria

Question 28

What does the primitive ventricle become

Answer 28

Left ventricle

Question 29

What does the Bulbus cordis become

Answer 29

right ventricle and outflow tracts for both ventricles (aorta and pulmonary trunk)

Question 30

Formation of blood islands

Answer 30

Day 17 extraembryonic mesoderm. Core of haemoblasts surrounded by endothelial cells

Question 31

Vasculogenesis

Answer 31

Day 18 angioblasts (from splanchnopleuric mesoderm) coalesce to form angioblastic cords throughout embryonic disc • Vasculogenesis is added to by angiogenesis- driven by angiogenic growth factors and takes place via proliferation and sprouting

Question 32

What drives embryonic vessel development

Answer 32

• Angiogenic growth factors – vascular endothelial growth factor, angiopoietin 1 & 2 • Repulsive signals – Plexin / semaphorin signalling, ephrin / Eph interactions • Attractive signals- VEGF

Question 33

Fetal Heart shunts

Answer 33

bypassing pulmonary circulation- not require in utero • Foramen Ovale - between atria • Ductus Arteriosus - pulmonary artery to aorta

Question 34

Umbilical vein

Answer 34

Carries oxygenated blood

Question 35

Umbilical artery

Answer 35

Carries deoxygenated blood

Question 36

Endocardial cushions

Answer 36

Masses of tissue called endocardial cushions grow from the sides of the atrioventricular canal to partition it into 2 separate openings • As the endocardial cushions grow together, the atrioventricular canal also is repositioned to the right of the heart

Question 37

5th aortic arch

Answer 37

Regresses

Question 38

Extra-embryonic blood vessel formation Day 17-21

Answer 38

Lateral plate mesoderm -> blood islands -> vasculogenesis

Question 39

Extra-embryonic blood vessel formation Day 28

Answer 39

Angiogenesis - proliferation and sprouting -> mesodermal cells recruited for tunica, media and adventitia

Question 40

Ductus arteriosus becomes…

Answer 40

Ligamentum arteriosum

Question 41

Foramen ovale becomes …

Answer 41

Fossa oval is

Question 42

Down and forwards cardiac looping

Answer 42

23 days: bulbus cordis

Question 43

Up and back cardiac looping

Answer 43

24 days: primitive ventricle 35 days: primitive atrium and sinus venosus

Question 44

Left right axis determination

Answer 44

Nodes secrete nodal- circulates left due to ciliary movement

Question 45

What is the embryological derivative of the coronary sinus

Answer 45

Left horn of the sinus venosus

Question 46

What is the embryological derivative of the smooth part of the right atrium

Answer 46

Right horn of the sinus venosus

Question 47

What does the first heart field develop into

Answer 47

Left ventricle

Question 48

What does the second heart field develop into

Answer 48

Right ventricle Atria Outflow tracts

Question 49

Which part of the gastrula forms the CV system

Answer 49

Mesoderm

Question 50

Describe the process by which the first breath causes a transition from fetal circulation to post-natal circulation

Answer 50

Expands lungs causing pulmonary vasodilation Reduces pulmonary pressure Pulmonary shunt closes Increases left atrial pressure Foramen ovale closes

Question 51

A 23 year old man with Marfan’s syndrome is found to have a dilated aortic root. Which embryological structure gives rise to the aortic root?

Answer 51

Truncus arteriosus