Embryology of the cardiovascular system Flashcards
What tissue forms the circulatory system?
Lateral plate splanchnic mesoderm
What does the lateral plate mesoderm spit into?
Somatic mesoderm - forms body wall structures e.g. bone, muscle
Splanchnic mesoderm - forms organs
When do the angioblastic cords first appear in the cardiogenic mesoderm?
3rd week of development
What tissue make up the two layers of the pericardium?
Parietal layer of serous and fibrous pericardium = somatic mesoderm
Visceral layer of serous pericardium = splanchnic mesoderm
What makes up the caudal end of the fused primitive heart tube?
Sinus venosus
Atrium
What makes up the cranial end of the fused primitive heart tube?
Ventricle
Bulbus cordis
Truncus arteriosus
What vein is responsible for the yolk sac?
Vitelline vein
What vein is responsible for the placenta?
Umbilical vein
What vein is responsible for the body of the embryo?
Common cardinal vein
How many pairs of aortic arches are there from the trunks arteriosus?
6 pairs
How does looping occur with the primitive heart tube?
Bulbus cordis and ventricle grow faster than other regions, growing heavy and pulling these down to form a U-shaped bulboventricular loop
What is dextrocardia?
Heart loops to the LEFT instead of the right, thus the heart lies to the right side of the body
What is the most common position abnormality of the heart?
Dextrocardia
When does partitioning of the primordial heart occur?
27th-37th days of embryonic development
What does endocardial cushion formation cause?
Separation of the right and left atrioventricular openings
What does septum formation cause?
Separates right atrium from left atrium and right ventricle from left ventricle
When does the septum primum develop?
End of 4th week, forming the foramen primum between the septum primum and the endocardial cushion
What leads to the development of the formamen secondum?
Apoptosis induced perforation of the septum primum causes part of it to break off and float towards the endocardial cushion, forming two foramen either side, before the fragment eventually fuses to the cushion, leaving the foramen secondum
To which side of the septum primum does the septum secondum develop?
Right
When does the septum secondum develop?
5th and 6th week of development
Describe the formation of the foramen ovale
Septum secondum grows and slightly overlaps septum primum, but leaves a incomplete partition allowing the flow of blood from the right atrium to the left atrium in the embryo
What causes the foramen ovale to close and form the fossa ovalis after birth?
Increased pulmonary blood flow and shift of pressure to the left atrium
What condition is associated with the non-closure of the foramen ovalis?
Atrial septal defect (ASD), “hole in the heart”
Describe the 4 main clinically significant types of ASD
Foramen secondum defect
Endocardial cushion + septum primum defect
Sinus venous defect
Common atrium
What are the two most common types of ASD
Foramen secondum defect
Endocardial cushion + septum primum defect
Why are females more prone to ASD?
Tend to develop more quickly, meaning more likely for mistakes to occur
Describe the partitioning of the bulbs corgis and trunks arteriosus
5th week
Neural crests in walls of both proliferate
Ridges form between each
These undergo 180 degree spiralling to form the aorticopulmonary (conotruncal) septum
Describe the separation of the primordial ventricles
Muscular ventricular septum forms
Interventricular foramen left
Aorticopulmonary septum forms and fuses with the muscular ventricular septum, closing the interventricular septum
Endocardial cushion grows and separates the atria from the ventricles
What is the most common type of congenital heart disease?
Ventricular septal defect (25% of cases)
What is the cause of cot death or sudden infant death syndrome?
Abnormalities of the conduction system of the heart
What primordial heart tubes makes up the right atrium?
Sinus venosus
What part of the adult heart is made up from the primitive atrium?
Parts of the left and right atrium
What primordial heart tubes makes up the left ventricle?
Primitive ventricle
What primordial heart tubes makes up the right ventricle?
Bulbus cordis
Name some common causes of congenital heart disease
Rubella infection in pregnancy (PDA) Maternal alcohol abuse (septal defects) Drug use and radiation Genetic Chromosomal
What is a common cause of cyanotic disease in newborns?
Transposition of the great vessels, usually associated with ASD and VSD
What 4 defects make up tetralogy of fallot?
Pulmonary stenosis
VSD
Dextroposition of the aorta
Right ventricular hypertrophy
What are some signs of tetralogy of fallot?
Blue Tet spells Murmur Finger clubbing Tire during breastfeeding
Whats the difference between vasculogenesis and angiogenesis?
V - formation of new network of vessels
A - growth of new vessels from existing blood vessels
What are the first arteries to appear in the embryo?
Right and left aortae
Whats the fate of the 1st and 2nd aortic arch?
Maxillary arteries (1st), 2nd disappears
What is the fate of the 3rd aortic arch?
common and internal carotid artery (and therefore the carotid arch)
What is the fate of the 4th aortic arch?
Left side - arch of aorta
Right side - right subclavian artery
What is the fate of the 5th aortic arch?
Never forms completely and regresses
What is the fate of the 6th aortic arch?
Right pulmonary artery from proximal right arch
Left pulmonary artery and ductus arteriosus from left arch
What is the ductus arteriosus?
Blood vessels that connects the pulmonary artery to the proximal descending aorta, which normally closes to form the ligamentum arteriosum within 1-3 months following birth
Describe the clinical effects aberrant subclavian artery
3rd branch of ascending aorta is abnormally found on the left side, meaning it has to loop back over the trachea and oesophagus to supply the right arm, which can be constricted although usually there are no clinical signs
Describe the clinical effects of a double aortic arch
Abnormal right and left aortic arch, forming a ring around the trachea and oesophagus, which can cause difficulty when swallowing and breathing
What are the signs of patent ductus arteriosus?
Increased effort in breathing
Poor weight gain in first year of life
Can lead to congestive HF if not found
Where is coarctation of the aorta most common?
Aortic arch
What arteries supply the yolk sac?
Vitelline arteries
What arteries supply the placenta?
Umbilical arteries
Describe the fate of the vitelline arteries
Form major arteries of the gut:
- celiac artery - foregut
- superior mesenteric artery - midgut
- inferior mesenteric artery - hindgut
Describe the fate of the umbilical arteries
Proximal portion persists as internal iliac and superior vertical branches to bladder
Distal portion degenerates and forms medial umbilical ligaments
Describe the fate of the cardinal veins
Become major vessels of the liver:
- portal vein
- hepatocardiac part of IVC
- liver sinusoids
- superior mesenteric vein
Describe the fate of the umbilical veins
Right - degenerates completely
Left - degenerates and forms ligamentum trees hepatis
Ductus venosus - obliterates and forms ligamentum venous
What is the ductus venosus?
Shunts blood from left umbilical vein to the inferior vena cava, allowing oxygenated blood from the placenta to bypass the liver
Describe the initial development of the lymphatic system
End of 6th week, develop around main veins
Six primary lymph sacs develop at end of embryonic period and fuse with vessels later on
Who are more likely to develop patent ductus arteriosus?
Females
Maternal rubella infection
Premature babies
What causes patent ductus arteriosus?
Failure of muscular wall to contract
Respiratory distress syndrome
Lack of surfactant in lungs
What reasons do people think cause coarctation of the aorta alongside ductus arteriosus?
Incorporation of muscle tissue from DA into aortic arch, so when DA contracts with birth, it also constricts the aorta
Genetic/environmental factors
