CVS EMBRYOLOGY Flashcards
what are the first arteries to appear in the embryo
right and left primitive aortae
what does each primitive aorta have
ventral and a dorsal aorta
how is aortic sac formed
fusion of the 2 ventral aortae, then becomes an extension of the truncus arteriosus
where do aortic arch branches arise from
aortic sac
in what weeks of pregnancy are the 6 pairs of aortic arches formed?
4th and 5th weeks
what happens during the 4th and 5th weeks of pregnancy
6 pairs of aortic arches are formed -> these unite with the dorsal aortae
what do aortic arches give rise to
great arteries of head and neck
by what 2 methods to blood vessels develop
vasculogenesis and angiogenesis
what is vasculogenesis
new formation of a primitive vascular network
what is angiogenesis
growth of new vessels from pre-existing blood vessels
explain the adult derivatives of aortic arches
1st and 2nd arches disappear early
3rd aortic arch forms common carotid artery
4th right arch forms right subclavian artery
4th left arch forms aortic arch
5th arch disappears
6th right arch forms right pulmonary artery
6th left arch forms the left pulmonary artery & ductus arteriosus
explain double aortic arch
occurs with the non-regression of the right aortic arch forming a vascular ring around the trachea and oesophagus, which usually causes difficulty in breathing and swallowing
explain patent ductus arteriosus (PDA)
common anomaly associated with maternal rubella infection in early pregnancy
cause - failure of muscular wall to contract, resp distress syndrome (low O2) and lack of surfactant in lungs
what can an uncorrected PDA lead to
congestive heart failure with increasing age
can be associated with ASD, VSD, coarctation of aorta
explain coarctation(constriction) of aorta
congenital condition where aorta is narrow , usually where ductus arteriosus (ligamentum arteriosum) inserts
most common in the aortic arch
can be proximal to ductus arteriosus (preductal) or distal to it (postductal)
what are the main theories of cause of coarctation of aorta
when ductus arteriosus contracts after birth, part of the arch attaching to it also constricts
genetic/environmental
vitelline vessels supply yolk sac
adult gut vessels
umbilical vessels supply placenta
internal iliac
cardinal vessels supply rest of body
SVC & IVC
in what week of pregnancy does lymphatic system begin to develop
week 6
explain development of lymphatic system during 6th week of pregnancy
develops around main veins
6 primary lymph sacs develops at the end of embryonic period
thoracic duct develops from two vessels anterior to the aorta - these become left and right embryonic thoracic ducts
left one gives rise to the upper third of the adult thoracic duct and the lower 2/3 of the adult duct are formed by right embryonic thoracic duct
what 2 organs does the placenta act for for the foetus
lungs and kidney
how does oxygenated blood reach foetus
comes from placenta and then reaches foetal IVC via umbilical vein, mostly bypassing foetal liver
blood in foetal IVC therefore mixed oxygenated and deoxygenated
foetus ductus venosus shunts
shunts blood in left umbilical vein into IVC : allows oxygenated blood from the placenta to bypass the liver
foramen ovale foetus shunt
shunts blood from right atrium to left atrium : allows blood to bypass the lungs
ductus arteriosus foetus shunt
shunts blood from right ventricle and pulmonary arteries to aorta : allows blood to bypass the lungs
ductus venosus
ligamentum venosum of the liver
foramen ovale
fossa ovalis of the heart
ductus arteriosus
ligamentum arteriosum between left and right pulmonary artery and aorta
umbilical arteries
medial umbilical ligaments of anterior abdominal wall
main stages in heart development
bilateral heart primordia primitive heart tube heart looping atrial and ventricular septation outflow tract septation
what week does CVS system function
first major system to function in embryo and this happens in week 4
Why does CVS function so early?
rapidly growing embryo - nutrition by diffusion is not sufficient to satisfy the growing embryo
what happens during 3rd week in terms of CVS development?
blood vessels “islands” first appear in yolk sac, allantois, connecting stalk and chorion - this is called the cardiogenic field
what do blood vessels in lateral plate splanchnic mesoderm form?
two heart tubes
two heart tubes are formed by…
blood vessels in lateral plate splanchnic mesoderm
when heart tubes fuse they form…?
join blood vessels in other areas to form primordial CVS system
somatic mesoderm
parietal layer of serous pericardium & fibrous pericardium form from this
splanchnic mesoderm
visceral layer of serous pericardium forms from
intra-embryonic coelom
pericardial cavity forms from
explain primitive heart tube - different parts
truncus arteriosus bulbus cordis primitive ventricle primitive atrium sinus venosus
what happens to primitive heart tube when it gets to big
invaginates pericardium
because it becomes too large for pericardium it needs to fold/loop and then goes onto form bulboventricular loop
explain formation of cardiac (bulboventricular) loop
bulbus cordis and ventricle enlarge and loop to right -> ventricle pushed left and inferiorly
atria are pushed superiorly and posteriorly
explains dextrocardia
heart tube loops to left side (instead of right side), so ventricles come to lie facing the right (=dextro)
most frequent positional abnormality of heart
explain partitioning of primitive heart
- single atrioventricular canal into left and right AV canals (endocardial cushion growth)
- the primitive atrium into left and right atria (atrial septum formation)
- the primitive ventricle into left and right ventricles (ventricular septum formation)
- the atria from the ventricles (heart valve formation)
-> this involves two actively growing masses of tissue : endocardial cushions and heart septae
explain endocardial cushion growth
separates RA + V from LA + V to form L & R AV canals
partitioning of primitive atrium into left and right atria
formation of septum primum & ostium primum
ostium secundum begins to form by apoptosis of part of septum primum
formation of septum secundum and formation of ostium secundum is complete , closure of ostium primum as septum primum meets the endocardial cushions
formation of foramen ovale is complete
what is the role of the foramen ovale before birth
allows most of the blood to pass from the right atrium to the left atrium (non-functioning lung)
prevents passage of blood in the opposite direction
what is the role of the foramen ovale after birth
normally closes (increased pressure in the LA due to increased pulmonary circulation) septum primum fuses with septum secundum fossa ovalis ( a depression in the interatrial septum) of adult heart is remnant of foetal foramen ovale
what does non-closure of the PFO result in
common form of congenital Atrial Septal Defect (ASD) - “hole in the heart”
explain partitioning of primitive ventricle
muscular ventricular septum forms. - opening is called interventricular foramen
aorticopulmonary septum divides bulbis cordis and truncus arteriosus into aorta and pulmonary trunk, bottom of spiral aorticopulmonary septum fuses with muscular ventricular septum and endocardial cushions to form membranous interventricular septum, closing interventricular foramen
explain ventricular septal defect
most common type of CHD (congenital heart disease) - 25% of defects
can appear in any part of septum
small VSDs close spontaneously (30-50%)
membranous type of VSD is most common
what week of pregnancy does partitioning of bulbus cordis(BC) and truncus arteriosus (TA) happen?
week5 - aorticopulmonary septum divides BC and TA into aorta and pulmonary trunk
explain transposition of great vessels
common cause of cyanotic disease in newborn infants
associated with ASD and VSD
permit exchange of systemic and pulmonary circulation eg tetralogy of fallot
Cause - 1. failure of aorticopulmonary septum to take a spiral course
2. defective migration of neural crest cells to heart
what develops from the ventricular wall (in terms of valves)
cusps, chordae tendinae and papillary muscles of the atrioventricular valves
semilunar valves are formed from…
subendocardial valve tissue
explain development of conducting system of the heart
early pacemakers are cardiomyocytes in primitive atrium and sinus venosus
clinical - cot death or sudden infant death syndrome (SIDS)
cause - abnormalities in conducting tissue
in week 5 of pregnancy what develops in regard to conducting system of the heart
SA node (pacemaker)
adult location of SA node
high in the RA near the entrance of SVC
AV node and bundle
bundle of His - develops from cells of AV canal and sinus venosus
aortic sac
aortic arches
bulbis cordis
right ventricle
parts of outflow tracts
primitive ventricle
left ventricle
primitive atrium
parts of RA and LA
sinus venosus
SVC & RA
lateral plate mesoderm
mesenteries, lining of pleural, cardiac and abdominal cavities, and the major substance of the heart
