Cardiac Embryology

Question 1

Which organ is the first to form in the developing embryo?

Answer 1

The cardiovascular system

Question 2

From which germ layer does the cardiovascular system arise?

Answer 2

Splanchnic lateral plate mesoderm

Question 3

What are the three germ layers called?

Answer 3

Ectoderm, mesoderm and endoderm

Question 4

How does mesoderm subdivide?

Answer 4

Paraxial mesoderm, intermediate plate mesoderm, lateral plate mesoderm (somatic and splanchnic)

Question 5

How do somites subdivide?

Answer 5

Dermatomes, myotomes and sclerotomes

Question 6

What do dermatomes, myotomes and sclerotomes form respectively?

Answer 6

Dermis of skin (dermatome), muscle (myotome) and bone (sclerotome)

Question 7

What are the four main stages in heart development?

Answer 7

1. Heart primordia fusing to make primitive heart tube
2. Heart looping
3. Atrial and ventricular septa forming
4. Outflow tract septation

Question 8

During which week of development does the heart start functioning (and beating)?

Answer 8

Around week 4 (beating around day 24)

Question 9

What are the regions of the primitive heart tube from bottom to top (inlet to outlet)?

Answer 9

Sinus venosus
Atrium
Ventricle
Bulbus cordis
Truncus arteriosum

Question 10

What are the three veins on either horn of the sinus venosus which drain into it in an embryo?

Answer 10

Vitelline vein; Umbilical vein; Common cardinal vein

Question 11

What do the vitelline, umbilical and common cardinal veins drain respectively?

Answer 11

Yolk sac; Placenta; Embryo body

Question 12

Which region of the primitive heart tube gives rise to the right ventricle?

Answer 12

Bulbus cordis

Question 13

Where is the foramen ovale found?

Answer 13

In interatrial septum secundum

Question 14

How are the aorta and the pulmonary trunk formed and separated?

Answer 14

Top part of bulbus cordis and truncus arteriosus undergo spiral septation

Question 15

What region of the primitive heart tube gives rise to the left atrium?

Answer 15

Primitive atrium

Question 16

What region of the primitive heart tube gives rise to the right atrium?

Answer 16

Sinus venosus

Question 17

What region of the primitive heart tube gives rise to the aorta and pulmonary trunk?

Answer 17

Truncus arteriosus

Question 18

List the four defects in Tetralogy of Fallot

Answer 18

1. Pulmonary stenosis
2. RV Hypertrophy
3. Ventricular Septal Defect
4. Overriding aorta

Question 19

What causes Tetralogy of Fallot?

Answer 19

Anterior displacement of aorticopulmonary septum in truncus arteriosus (larger space for aorta and smaller for pulmonary trunk)

Question 20

What heart defect is often found in Turner’s Syndrome?

Answer 20

Aortic coarctation

Question 21

What heart defect is often found in Down’s Syndrome?

Answer 21

VSD

Question 22

Which sex is more likely to develop atrial septal defect?

Answer 22

Females

Question 23

Which sex is more likely to develop ventricular septal defect?

Answer 23

Males

Question 24

What is transposition of the great arteries?

Answer 24

Aorta coming off right ventricle and pulmonary trunk coming off left ventricle

Question 25

What are the two causes of transposition of the great arteries?

Answer 25

1. Failed spiral septation | 2. Abnormal neural crest cells migration

Question 26

Which two congenital abnormalities are more common in females?

Answer 26

ASD and patent ductus arteriosus (PDA)

Question 27

What makes up the membranous interventricular septum?

Answer 27

The bottom of the spiralled aorticopulmonary septum

Question 28

What happens to the first and second aortic arches?

Answer 28

Becomes the maxillary arteries coming off the external carotid arteries

Question 29

What happens to the third aortic arches?

Answer 29

Become carotid arches (form internal carotid arteries)

Question 30

What happens to the fourth aortic arches?

Answer 30

Right - becomes right subclavian artery | Left - becomes aortic arch

Question 31

What happens to the fifth aortic arches?

Answer 31

Disappear or don't appear at all

Question 32

What happens to the sixth aortic arches?

Answer 32

Right - becomes proximal end of right pulmonary artery | Left - becomes left pulmonary artery and forms ductus arteriosus (later ligamentum arteriosum)

Question 33

List four common heart defects associated with aortic arches

Answer 33

1. Aberrant subclavian artery 2. Coarctation of aorta 3. Double aortic arch 4. Patent Ductus Arteriosus (PDA)

Question 34

What happens to the embryonic umbilical arteries?

Answer 34

Proximal end - become internal iliac and superior vesical arteries Distal end - become umbilical ligaments

Question 35

What happens to the embryonic vitelline veins?

Answer 35

They become part of the hepatic portal circulation

Question 36

Name the three main embryonic circulation bypass structures and their function

Answer 36

1. Ductus venosus (allows blood to bypass liver) 2. Ductus arteriosus (allows blood to bypass lungs) 3. Foramen ovale (allows blood to bypass lungs)

Question 37

What happens to the ductus venosus, ductus arteriosus and foramen ovale after birth?

Answer 37

They become ligamentum venosus, ligamentum arteriosus and fossa ovale

Question 38

What disease often causes patent ductus arteriosus (PDA)?

Answer 38

Maternal rubella during early pregnancy

Question 39

What happens to the umbilical veins?

Answer 39

Right - disappears | Left - becomes ligamentum teres in liver

Question 40

What happens to the cardinal veins?

Answer 40

They anastomose and become the IVC and SVC

Question 41

List the abnormalities that can occur in IVC and SVC development

Answer 41

Double IVC, double SVC, absent IVC, left SVC