Embryology CVS 1 Flashcards
what happens in the first major stage of heart development?
primitive heart tube is formed
what happens in the second major stage of heart development?
heart looping
what happens in the third major stage of heart development?
atrial and ventricular septation
what happens in the fourth major stage of heart development?
outflow tract septation
what happens during week 3 of development (not same as stage 3)
Lateral plate splanchnic mesoderm forms circulatory system (and other viscera)
Angiogenic cell islands collect in
the lateral plate splanchnic mesoderm, move towards the midline and coalesce to form the two primitive heart tubes
which is the first major system to function in the embryo
cardiovascular system
when does the primordial heart start to function? why?
at the beginning of week 4
rapidly growing embryo - nutrition diffusion is not enough to satisfy the growing embryo
where do blood vessels first appear?
in the wall of the yolk sac, allantois, connecting stalk and chorion
what do angioblastic cords canalize to form?
heart tubes
Angioblastic cords arrange themselves side by side to form the primordia of the endocardial tubes.
what is the pericardium derived from
intra-embyronic coelem
what is the visceral layer of serous pericardium derived from?
splanchnic mesoderm
what is the parietal layer of serous pericardium formed from?
somatic mesoderm
the tubular heart joins blood vessels in other areas to form what?
primordial cardiovascular system
where do aortic arches arise from?
aortic sac
where does the right ventricle and parts of the outflow tracts arise from?
bulbus cordis
where does the left ventricle arise from
primitive ventricle
where do parts of the right and left atria arise from
primitive atrium
where does the superior vena cave and right atrium arise from
sinus venosus
describe the sinus venosus in the primitive heart tube
it has two horns R and L
each horn gets venous blood from - yolk sac, placenta and body of the embryo
where do the aortic arches terminate
in the dorsal aorta
the bulbus cordis (in the primitive heart tube) and ventricle grow faster than other regions forming what?
a U-shaped bulboventricular loop
Clinical:-
Dextrocardio
congenital disease where the heart tube loops to the right (instead of to the left)
most frequent positional abnormality of the heart
what happens around 27th and 37th days (towards end of 4th week) of embryonic development?
endocardial cushion formation - separates R atrium and ventricle from L atrium and ventricle to form L and R AV canals
septum formation - separates right atrium from left atrium and right ventricle from left ventricle
which 2 septum and 2 foramen form at the end of the 4th week
septum primum
septum secundum
foramen primum
foramen secundum
stage 1 of L and R atria separation
septum primum growth generates foramen primum as it protrudes downwards from top of atrium
stage 2 of L and R atria separation
foramen secundum is formed on the upper end of septum primum (due to cell death)
stage 3 of L and R atria separation
septum secundum grows on the right of septum primum
stage 4 of L and R atria separation
septum secundum grows down and overlaps the foramen secundum. But septum secundum is incomplete - perforated by foramen ovale
where does the foramen secundum open in
the septum primum
where does the foramen ovale open in
septum secundum
role of oval foramen before birth?
Allows most of the blood to pass from the right atrium to the left atrium (non functioning lung)
Prevents the passage of blood in the opposite direction
role of oval foramen after birth?
Normally closes (increased pulmonary blood flow and shift of pressure to the left atrium)
Septum primum (= valve of oval foramen) fuses with the septum secundum
Oval fossa (fossa ovalis) of adult heart is a remnant of foetal oval foramen
Non closure results in Atrial Septal Defect (ASD) – “Hole in the heart”
Atrial Septal Defect (ASD)
Common congenital heart anomaly
More common in females than in males
Common form – patent foramen ovale
what are the 4 clinically significant types of ASD?
Foramen secundum defect
Endocardial cushion defect with foramen primum defect
Sinus venosus defect
Common atrium
what are 2 most common types of ASD
Foramen secundum defect
Endocardial cushion defect with foramen primum defect
3 stages of partitioning of primitive ventricle
- Muscular ventricular septum forms. Opening is called interventricular foramen
- Bottom of spiral aorticopulmonary septum fuses with muscular ventricular septum to form membranous interventricular septum, closing interventricular foramen. (Aorticopulmonary septum divides bulbis cordis and truncus arteriosus into aorta and pulmonary trunk)
- Growth of endocardial cushions also contributes to membranous portion of the interventricular septum.
what happens during the 5th week of embryonic development?
aorticopulmonary septum divides BC and TA into aorta and pulmonary trunk
Ventricular Septal Defect (VSD)
Most common type of CHD (congenital heart disease) – 25% of defects
Common in males
Can appear in any part of septum
Small VSDs close spontaneously (30 -50%)
Membranous type of VSD is most common
development of the conducting system of the heart
Early pacemakers - primitive atrium and then sinus venosus
SA node (pacemaker) develops during 5th week
Adult location of SA node – High in the right atrium near the entrance of the SVC
AV node and bundle (bundle of His) develops from cells of AV canal and sinus venosus
how does cot death or sudden infant death syndrome come about?
abnormalities of conducting tissue
transposition of great vessels - what is it?
abnormal positioning of the great vessels ie aorta coming from left ventricle instead of right etc
Associated with ASD and VSD
Permit exchange of systemic and pulmonary circulation
cause of transposition of great vessels?
Failure of aorticopulmonary septum to take a spiral course
Defective migration of neural crest cells
eg. Tetralogy of Fallot
what is tetralogy of Fallot
A combo of 4 cardiac defects:
Pulmonary stenosis (obstruction of right ventricular outflow)
Ventricular septal defect (VSD)
Dextroposition of aorta (“overriding” aorta)
Right ventricular hypertrophy
cause of Tetralogy of Fallot
Unequal division of the conus due to anterior displacement of aorticopulmonary septum
causes of congenital heart disease? (5)
Rubella infection in pregnancy (PDA)
Maternal alcohol abuse (septal defects)
Maternal drug treatment and radiation
Genetic - 8%
Chromosomal – 2% (Down’s and Turner’s syndrome)
