Development of Cardiovascular System Flashcards
Stages of Embryonic heart development
Linear Heart Tube Formation --> Formation of the cardiac loop --> Heart septation --> Cavitation of ventricle Formation of valves & great vessels --> 4-chambered heart
Describe the regions found anteriorly on the linear heart tube at approx day 22 of embryonic development
Think of the bottom as the inflow part and the top as the outflow part
Dorsal Mesocardium
Structure that keeps the linear heart tube attaches to the body of the embryo
Describe the lining of the heart tube
Endocardial lining with a myocardial layer
What does the truncus arteriosus form in an adult heart
Most of the proximal aorta and pulmonary trunk
What does the bulbus cordis form in an adult heart
Right Ventricle
What does the ventricle region of the heart tube form in an adult heart
Left Ventricle
What does the atrium region of the heart tube form in an adult heart
Trabeculated portions of RA & LA
What does the left sinus venosus horn form in an adult heart
Coronary Sinus
What does the right sinus venosus horn form in an adult heart
Smooth wall of right atrium
Conus Cordis
Be vaguely aware of this structure as being part of the outflow tract
Which parts of the heart tube grow the fastest and what does this lead to
Ventricles and bulbus cordis
Leads to the heart bending in a rightward direction, leading to the atrium and sinus venosus moving cranially and dorsally when originally being caudal to the ventricle
When the cardiac loop is formed, describe the septation of the heart
At that point there is no septation and the right/left atria and right/left ventricles are continuous with one another
Name the 3 Endocardial Cushions and their positions
Cushions in AV region
In outflow region - conal cushions and truncal cushions (sometimes outflow cushions referred to as ridges)
What do the endocardial cushions look like
They are localised swellings in the outflow tract and AV canal full of matrix
What happens to the endocardial cushions as the embryo developsg
They thicken and protrude into the lumen
Cells from endothelial lining activate and migrate into endocardial cushion matrix and make it cellular
Role of endocardial cushions in embryonic development
They play a major role in normal heart septation and normal cardiac valve formation
Describe the formation of the foramen secondum
A little septum primum grows down into the foramen primum. Apoptosis leads to a bunch of perforations in the septum primum as it forms - the perforations then re-fuse and leave two openings; foramen primum above the endocardial cushion and foramen secondum between the strip of joint cells and septum primum
Describe the events leading to formation of valve of foramen ovale after foramen secundum formation
The strip of cells that have joined fuse together with the endocardial cushions, leaving behind only the foramen secundum
Simultaneously a developing septum secundum forms adjacent to the previous septum which grows down, eventually overlapping with the primum
This leaves the valve of the foramen ovale between RA and LA in an embryo made by the septum primum
Describe the septation of the primitive ventricle
Myoblast proliferation leads to cells growing up from the ventricular floor towards the endocardial cushions in the AV canal
By 6 weeks there is still an interventricular foramen; it is closed by a membranous portion though and forms a septum
How do AV valves form
Endocardial cushions undergo modification and restructuring to give rise to the cusps of valves
(Diagram gives a lot of extra info, all you really need to know is the text above)
How do the great vessels form
Tube coming out of the heart
What shape do the ridges in the outflow tract make (Truncal ridge and bulbar ridge)
They form a continuous spiral-like shape as they change from being lateral and at other times being dorsal and ventral
What is the result of the truncal and bulbar ridge spiral formation
The ridges join along the spiral to form a septum. This separates the pulmonary trunk and proximal part of the aorta into two different vessels that twist around one another
What tissue forms the semilunar valves
These valves are formed from the outflow endocardial cushions that specialise into valves
How do the SVC and IVC form
They are derived from primordial veins that undergo a series of changes during development, leading to their remodelling and incorporation into these new great vessels
How does the Pulmonary Vein form
Most of the smooth wall of the LA is derived from the primordial pulmonary vein and its branches; as the atrium expands, more PV is uncorporated until ultimately 4 are present
Compare pre and post natal circulation in the heart
The ductus arteriosis and oval foramen are the main differences to be aware of
Also just know that lungs here give back deoxygenated blood in prenatal circulation as those cells use the blood
What is the role of the ductus arteriosus
It takes blood straight to the aorta to go around the body such that the prenate’s lungs are not overloaded
Ligamentum arteriosum
Ligament present in healthy adults that is a remnant of the ductus arteriosus
What leads to the closure of the foramen ovale
Changes in pressure at birth as the baby breathes
Over the coming days and weeks, the cells fuse and entirely shut the foramen ovale
Is the foramen ovale prone to birth defects
Yes ffs yes it is
Have a vague awareness of cardiac development time
Ostium Secundum ASD
Atrial Septum Defect
A hole is formed in the centre of the atrial septum
Pathophysiology of Atrial Septal Defects
Enlarged RA, RV and/or PA
Also some considerable intracardiac shunting may occur
Ventricular Septal Defect and frequency
Most common CHD (approx 25%)
Can involve the muscular or membranous part of ventricular septum (usually involves membranous part failing normal development)
Can treat itself
