Thorax 8: Development of the Heart and Great Vessels

Question 1

How many weeks in does the bilaminar disc become trilaminar?

Answer 1

2 weeks post conception

Question 2

What are the 3 layers of the trilaminar disc?

Answer 2

• ectoderm
• mesoderm
• endoderm

Question 3

When is mesoderm formed?

Answer 3

during week 3

Question 4

Which layer of the disc does the heart tube form in and what end of the disc? What does it form from?

Answer 4

• mesoderm
• angiogenetic clusters as a horseshoe
• cephalic end

Question 5

Which day does heart development start to occur? Why?

Answer 5

-day 18
-diffusion is no longer sufficient to provide nutrients
and development of both blood and vascular structures is necessary

Question 6

What folding happens to the heart tube? Where does this allow the heart tube to migrate to?

Answer 6

• cephalo-caudal folding

- heart tube migrates from the head through the neck to the thorax of the embryo

Question 7

What 3 types of cardium does the heart tube develop into? What do these become?

Answer 7

• Epicardium- visceral pericardium
• Myocardium- cardiac muscle
• Endocardium- endothelial lining

Question 8

When does looping and folding of the heart tube occur?

Answer 8

week 4 around 22 days

Question 9

What structures are at the caudal and cephalic end of the heart tube?

Answer 9

• sinus venosus

- Truncus arteriosus

Question 10

Which direction does the heart tube fold to? How does this orientate the heart?

Answer 10

• 2 ends fold towards each other and to the right

- apex of heart is pushed to the left. rotation means right side of heart is more anterior

Question 11

What happens to the heart 28 days in?

Answer 11

• heart pushes into the pericardial sac

- ventricles begin to trabeculate

Question 12

Which vessels does the venous end receive blood from?

Answer 12

• cardinal
• umbilical
• vitelline veins

Question 13

Which structure do the atria start to bulge out the side from?

Answer 13

bulbus cordis

Question 14

What structures are formed from the proximal, middle and distal parts of the bulbus cordis?

Answer 14

• proximal forms RV
• middle forms outflow of ventricles
• distal forms PT and aorta

Question 15

How are left and right caverns formed after growth from the bulbus cordis?

Answer 15

• bending causes narrowing, augmented by endocardial cushion growth
• endocardial cushion cells grow and then eventually begin to fuse forming left and right caverns

Question 16

What forms from enlargement of truncus arteriosus?

Answer 16

PT and aorta

Question 17

What 3 structures are formed as a result of the enlargement of the endocardial cushion cells?

Answer 17

• interatrial cells
• membranous part of the inter ventricular septum
• AV valves

Question 18

What is the first stage in the development of the foramen ovalis? What is the name of the first channel formed between the atria?

Answer 18

• formation of the septum primum in-between the atria , it grows down towards endocardial atrio-ventricular cushions
• ostium primum

Question 19

what is the second stage and final stage in the development of the foramen ovalis?

Answer 19

• formation of septum secundum in the right atrium, stiff and muscular, grows down but does not fuse with endocardial cushion
• ostium secundum

Question 20

Which opening forms the foramen ovalis? What becomes the name of the fossa in the septum primum?

Answer 20

• the ostium secundum = foramen ovalis

- the ostium primum becomes the ostium secundum

Question 21

Which weeks is the foramen ovalis formed by?

Answer 21

between weeks 5 and 6

Question 22

What is a patent foramen ovale? How is it caused?

Answer 22

• the foramen ovale didn’t close the way it should have at birth
• caused by excessive cell death or reabsorption of the septum primum

Question 23

Which week is the inter ventricular septum complete by?

Answer 23

week 7

Question 24

how are left and right ridges formed in the conus?

Answer 24

endocardial cushion cells

Question 25

What is formed from extension of the atria-ventricular cushion?

Answer 25

membranous portion of inter ventricular septum

Question 26

How is the conotruncal septum formed?

Answer 26

L+R truncal ridges spiralling

Question 27

How is the inter ventricular foramen closed?

Answer 27

- Membranous part of the inter ventricular septum - inferior growth of truncal ridges - inferior atrio-ventricular septum

Question 28

What happens if no truncal ridges develop?

Answer 28

Persistent truncus arteriosus

Question 29

What results if no spiral occurs in the great truncal ridges?

Answer 29

Transposition of the great vessels

Question 30

What happens to the truncal septum in tetralogy of Fallot?

Answer 30

septum deviates right and does not meet the inter ventricular septum

Question 31

Why does the heart show RV hypertrophy in tetralogy of Fallot?

Answer 31

pulmonary stenosis= narrowing of the pulmonary valve to artery hence RV has to work harder to pump blood into the pulmonary circulation

Question 32

What needs to be incorporated during atrial growth?

Answer 32

adjacent veins

Question 33

During development of the atria what change can be seen in the wall of the atrium, especially in the RA?

Answer 33

cristae terminalis mark the change and form the point for the formation of muscular ridges in the atrium

Question 34

how do ventricles grow in size?

Answer 34

balloon to grow around and away from the muscular septum dividing them

Question 35

How are atrioventricular valves formed?

Answer 35

endocardial cushion growth and cavitation to form papillary muscles and chordae tendinae

Question 36

How are the semi lunar valves formed?

Answer 36

hollowing of endocardial tubercles

Question 37

What is arterial development associated with? Which weeks do these occur?

Answer 37

- intimatley associated with sequential formation of pharyngeal arches with their own cranial nerve and arterial supplies - weeks 4+5

Question 38

What do arches give rise to?

Answer 38

structures in the head and neck

Question 39

What occurs as each pharyngeal arch develops?

Answer 39

arteries arise from aortic sac (part of truncus arteriosus=aorta) grows through the arch and joins the dorsal aorta

Question 40

How many pairs of aortic arches arise from truncus arteriosus?

Answer 40

6

Question 41

What are the first aortic arches responsible for?

Answer 41

maxillary arteries

Question 42

What aortic arch forms the common carotid arteries?

Answer 42

arch 3 with dorsal aorta

Question 43

What are aortic arch 4 left and right branches responsible for?

Answer 43

- left= aortic arch | - right=right subclavian artery

Question 44

What are aortic arch 6 left and right branches responsible for developing into?

Answer 44

- left= pulmonary trunk and ductus arteriosus | - right= contributes to PT

Question 45

What is Patent Ductus Arteriosus? What type of murmur can be heard?

Answer 45

- postnatally the aortic pressure is greater than the pulmonary trunk. Blood will flow back into pulmonary circulation - machinery murmur

Question 46

What is coarctation of the aorta?

Answer 46

aortic narrowing after origin of L subclavian vein due to an abnormality in aortic media and intimal proliferation

Question 47

What effect does coarctation have on the femoral pulses?

Answer 47

weakens them

Question 48

What type of coarctation is most common? What happens to blood flow?

Answer 48

- postductal | - blood travels in subclavian to internal thoracic to intercostal vessels and back to thoracic aorta

Question 49

Which nerve do the recurrent laryngeal nerves branch from? Which aortic arch do the hook around?

Answer 49

- vagus nerves | - 6

Question 50

Why is the left recurrent laryngeal nerve carried into the thorax?

Answer 50

the aortic arch persists as ductus arteriosus and ligamentum areteriosum so the nerve is carried into the thorax

Question 51

Why does the right recurrent laryngeal nerve not end up in the thorax?

Answer 51

both the 5th and 6th right aortic arches regress so the nerve hooks around the 4 aortic arch which becomes the right subclavian artery in the root of the neck