cardio embryology

Question 1

What are the 5 big stages in the development of the heart?

Answer 1

Bilateral endocardial heart primordia 
Primitive heart tube 
Heart looping 
Atrial and ventricular separation 
Outflow tract separation

Question 2

At what week does the cardiovascular system develop?

Answer 2

Around week 3/4

Question 3

At what week does the respiratory system develop?

Answer 3

Around week 4

Question 4

Stage 1 of the CVS development

Answer 4

From the lateral plate splanchnic mesoderm;

• Blood islands start to from all around the embryo (in the yolk sac, allantois, connecting stalk and chorion) forming the cardiogenic field
• The heart tubes from

Question 5

Stage 2 of the CVS development

Answer 5

The two heart tubes fuse to from the primordial cardiovascular system

Question 6

Stage 3 of the CVS development

Answer 6

Pericardial cavity is created which has developed from intra-embryonic coelom. It has a membranes surrounding it which has two side, the visceral side developed from the splanchnic mesoderm and the parietal side which develops from the somatic mesoderm.

Question 7

Stage 4 of the CVS development

Answer 7

Embryo folds so that the primordial cardiovascular system is dorsal to the pericardial cavity

Question 8

Stage 5 of the CVS development

Answer 8

The primitive heart tube starts to grow and develop. It grows to that it has 5 parts, the truncus arteriosus (cranial atrial end), the bulbus cordis, the primitive ventricle, the primitive atrium and the sinus venosus (caudal venous end).

Question 9

Stage 6 of the CVS development

Answer 9

The heart tube grows and becomes surrounded by the pericardial cavity.

Question 10

Stage 7 of the CVS development

Answer 10

The growing heart tube quickly runs out of space, especially the bulbs chords and ventricle which are growing fastest. So these two parts loop to the right pushing the ventricles left and down and the atria up and back. This forms the bulboventricular loop.

Question 11

Congenital condition 1

Answer 11

Dextrocardia where the heart loops to the left

Question 12

Stage 8 of the CVS development

Answer 12

Endocardial cushions grow from each side to create two atrioventricular canals. (A square in the middle which allow blood to pass into the atria on the left or right)

Question 13

Stage 9 of the CVS development

Answer 13

The septum primum grows to separate the left and right atrium. The gap at the bottom is called the ostium primum however this will close. The top of the septum primum then breaks down and this part is called the ostium secundum. This creates a gap called the foramen ovule.
The septum secundum also grown in and sits parallel to the septum primum it also has a hole but it is in a different place to the hole of the septum primum.
Foramen ovule allows blood to pass from the right atria to the left atria but will close. This happens when the two septum’s fuse and this may create a fossa ovalis.

Question 14

Congenital condition 2

Answer 14

PFO (patent foramen ovale) a type of ASP (atrial septal defect) where the foramen ovalis fails to close properly.

Question 15

Stage 10 of the CVS development

Answer 15

A muscular ventricular septum grows up and forms the first half of the interventricular septum. It leaves a gap called the interventricular foramen.

Question 16

Stage 11 of the CVS development

Answer 16

A aortopulmonary septum grows up in a spiral shape and divides the bulbis cordis and the truncus arteriosus into the aorta and pulmonary trunk.

Question 17

Stage 12 of the CVS development

Answer 17

The bottom of the aortopulmonary septum fuses with the endocardial cushion to from a membranous interventricular septum which closes off the interventricular foramen.

Question 18

Congenital condition 4

Answer 18

VSD Ventricular septal defects occur when there is a hole in the intraventricular septal

Question 19

Congenital condition 3

Answer 19

Transposition of the great vessels allows gas exchange between the systemic and pulmonary circulation.
This can happen because the aortopulmonary septum fails to take its spiral course (See picture) or because the defective migration of the neural crest cells to the heart.
Transposition if often associated with a ASD or VSD as well and can cause cyanotic disease in new-borns.
Tetralogy of Fallot is a condition where there is a ASD, VSD, transposition and enlargement of ventricles.

Question 20

Stage 13 of the CVS development

Answer 20

Cusps, chordae tendineae and papillary muscles of the atrioventricular valves develop from the ventricular wall.
The semilunar valves (Pulmonary and aorta) grow from the subendocardial valve tissue.

Question 21

Stage 14 of the CVS development

Answer 21

Cardiomyocytes are primitive pacemakers. In week 5 the SA node, AV node and bundle of His all start to develop. The AV node is in the interatrial septum.

Question 22

Congenital condition 5

Answer 22

Failure of the conducting system to from properly causes SIDS

Question 23

How do aortic arches from?

Answer 23

Right and left primitive aorta appear. They have a ventral end and a dorsal end and the aortic sac forms when the 2 ventral ends fuse.
The aortic sac then binds to the truncus arteriosus to from a continuation of that vessel.
The aortic sac then elongates and 6 Aortic branches arise from the aortic sac and loop to connect to the dorsal branches or the primitive aortas.

Question 24

What do the aortic arches go on to from?

Answer 24

1st pair or arches disappears
2ns pair of arches disappears
3rd pair or arches becomes the common carotid
4th right becomes the right subclavian. 4th left becomes the aortic arch.
5th pair disappears.
6th right and left becomes the right and left pulmonary arteries. Left also becomes the ductus arteriosus.

Question 25

4 arch anomalies

Answer 25

Right subclavian comes from the left not the right, wraps round the trachea and restricts it and the oesophagus
Double aortic arch forms a thick circle around the trachea and oesophagus which causes difficulties in breathing and swallowing.
Patent ductus arteriosus where there is an opening between the aorta and the pulmonary trunk. Occurs due to maternal rubella infection.
Coarctation of the aorta. They can be post ductal or preductal.

Question 26

What do the embryotic vessels from in adults ?

Answer 26

Vitelline vessels supply yolk sac becomes the adult gut vessels,
the umbilical vessels supply placenta becomes internal iliac and
the cardinal vessels supply rest of the body becomes the SVC and IVC.

Question 27

How does the lymphatic sacs and vessels from?

Answer 27

Development of the lymphatic system develops at the end of the sixth week around the main veins. Six primary lymph sacs develop at the end of the embryonic period. Lymphatic vessels will later join the lymph sacs later.

Question 28

How do lymphatic ducts from?

Answer 28

Thoracic duct develops form the two vessels anterior to the aorta. These becomes the left and right embryonic thoracic ducts. The left one gives rise to the upper third of the adult thoracic duct and the lower two thirds of the adult duct are formed by the right embryonic thoracic duct.

Question 29

what are the foetal shunts

Answer 29

. The ductus venous shunts blood in the left umbilical vein directly into the IVC allowing oxygenated blood from the placenta to bypass the liver.
The foramen ovule shunts blood form the right atrium to the left atrium allowing blood to bypass the lungs.
The ductus arteriosus shunts blood from the right ventricle and pulmonary arteries to the aorta allowing the blood to bypass the lungs.

Question 30

How do the foetal shunts close?

Answer 30

The ductus venous becomes the ligamentum venosum of the liver, the foramen ovule closes after birth to form the fossa ovalis of the heart, the ductus arteriosus becomes the ligamentous arteriosum between the left pulmonary artery and the aorta and the umbilical arteries become the medial umbilical ligaments of the anterior abdominal wall.