cardio embryology Flashcards
What are the 5 big stages in the development of the heart?
Bilateral endocardial heart primordia Primitive heart tube Heart looping Atrial and ventricular separation Outflow tract separation
At what week does the cardiovascular system develop?
Around week 3/4
At what week does the respiratory system develop?
Around week 4
Stage 1 of the CVS development
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
Stage 2 of the CVS development
The two heart tubes fuse to from the primordial cardiovascular system
Stage 3 of the CVS development
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.
Stage 4 of the CVS development
Embryo folds so that the primordial cardiovascular system is dorsal to the pericardial cavity
Stage 5 of the CVS development
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).
Stage 6 of the CVS development
The heart tube grows and becomes surrounded by the pericardial cavity.
Stage 7 of the CVS development
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.
Congenital condition 1
Dextrocardia where the heart loops to the left
Stage 8 of the CVS development
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)
Stage 9 of the CVS development
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.
Congenital condition 2
PFO (patent foramen ovale) a type of ASP (atrial septal defect) where the foramen ovalis fails to close properly.
Stage 10 of the CVS development
A muscular ventricular septum grows up and forms the first half of the interventricular septum. It leaves a gap called the interventricular foramen.
Stage 11 of the CVS development
A aortopulmonary septum grows up in a spiral shape and divides the bulbis cordis and the truncus arteriosus into the aorta and pulmonary trunk.
Stage 12 of the CVS development
The bottom of the aortopulmonary septum fuses with the endocardial cushion to from a membranous interventricular septum which closes off the interventricular foramen.
Congenital condition 4
VSD Ventricular septal defects occur when there is a hole in the intraventricular septal
Congenital condition 3
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.
Stage 13 of the CVS development
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.
Stage 14 of the CVS development
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.
Congenital condition 5
Failure of the conducting system to from properly causes SIDS
How do aortic arches from?
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.
What do the aortic arches go on to from?
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.
4 arch anomalies
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.
What do the embryotic vessels from in adults ?
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.
How does the lymphatic sacs and vessels from?
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.
How do lymphatic ducts from?
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.
what are the foetal shunts
. 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.
How do the foetal shunts close?
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.
