Development of Cardiovascular System Flashcards
Describe the stages of heart development
Linear heart tube formation Formation of the cardiac loop Heart septation Cavitation of ventricle, formation of valves and great vessels 4 chambered heart, not fully mature
Describe linear heart tube formation
Around day 22
Need picture
1st aortic arch, truncus arteriosus, conus cordis, bulbus cordis, ventricle, atrium, L/R sinus venosus horn
What makes the outflow tract/region?
Truncus arteriosus
Conus cordis
Bulbus cordis
What does the truncus arteriosus develop into?
Most of proximal aorta and pulmonary trunk
What will the bulbus cordis develop into?
Right ventricle
What will the ventricular region develop into?
Left ventricle
What will the left sinus venosus horn develop into?
Coronary sinus
What will the right sinus venosus horn develop into?
Smooth wall of RA
What is another name for sinus venosus?
Inflow region/tract
How does the cardiac loop form?
Ventricles and bulbus cordis of the heart grow faster than other regions, therefore the heart bends in the rightward direction
Leads to atrium and sinus venosus to move cranially and dorsally (initially caudal to ventricle)
Around what day is looping complete?
28th day
Name the endocardial cushions and describe where they are
- Atrioventricular cushions - AV canal
- Truncates cushions/ridges - top of OFT
- Canal cushions/ridges - below
What are endocardial cushions?
Extracellular matrix proteins
Localised swellings in the OFT and AV canal
What happens to the cushions?
Swell more as heart grows
‘Activated’ cells migrate into endocardial cushions
Cellularises with mesenchyme
Why are cushions essential?
Cardiac valve formation and sepation of the heart
When does septation of the primordial atrium occur?
4-6 weeks
What occurs in the first step of septation of the primordial atrium?
Septum primum lengthens
Perforations form
Gap is called foramen primum
What occurs in the second part of the septation of the primordial atrium?
Foramen secundum formed
Foramen primum closed
Septum secundum initiated
What occurs in the third part of the septation of the primordial atrium?
Valve of foramen ovale forms from septum primum (foramen ovale)
Septum primum degenerating
What occurs in the fourth part of the septation of the primordial atrium?
Foramen ovale closed by valve of foramen ovale
When does septation of the primitive ventricle occur?
5-20 weeks
Septation of the primitive ventricle
Interventricular septum grow up, closing the interventricular foramen
Made of thin membranous part of interventricular septum
Cavitation of the ventricle
Papillary muscles, chordae tendineae - attach wall of ventricles to the valves
Where are the mitral and tricuspid valves derived from?
Endocardial cushions
Takes weeks to develop - undergo modelling
Which vessels are derived from the outflow region?
Aorta
Pulmonary trunk
Formation of aorta and pulmonary trunk
Truncal and bulbar ridges are continuous, but positioning means they are spiralling round the outflow region of the heart
P
A separated by aortico-pulmonary septum
A P
A
P
Pulmonary trunk twists around ascending aorta
Development of semi-lunar valves (aortic and pulmonary valves)
When division of truncus arteriosus is nearly complete
Swellings begin to form near entrances
From endocardial cushions
Formation of SVC and IVC
Derived from primordial veins
Series of changes and remodelling and incorporation
Development of pulmonary veins
Most of the smooth wall of the LA is derived from primordial pulmonary vein and branches
As atrium expands, more of the PPV is incorporated until 4 veins present
What occurs in the heart at birth?
3 shunts close
Lungs expand - reduced resistance to blood flow
Pressure in RA < LA
Blood stops flowing through foramen ovale
How does the foramen ovale close?
After first breath:
RA has lower pressure than left, which closes the valve
The fossa ovalis fuses over it (thin area of septum)
What is the second shunt that closes postnatally?
Ductus arteriosus constructs
Leads to closure and ligamentum arteriosum forms
What is the third shunt that shuts postnatally?
Ductus venosus constricts
Leads to closure and ligamentum venosum in liver forms
When do lateral endocardial tubes form?
19 days
When is a primitive 4-chambered heart formed?
7 weeks
What are congenital heart defects usually caused by?
Single gene defect
Chromosomal anomaly
Exposure to teratogens
Examples of congenital heart disease
Atrial Septal Defects
Ventricular Septal Defects
Patent Ductus arteriosus
Tetralogy of fallout
Describe ASD
Atrial Septal defects
Common - 6.4/10,000 births
Ore common in females
Most clinically significant: ostium secundum ASD
Pathophysiology of ASD
Enlarged RA, RV and PA
Considerable intracardiac shunting may occur
Describe VSD
Ventricular Septal Defects
Most common
More common in males
Usually involves membranous part of interventricular septum fails to develop normally
Tetralogy of fallot
combination of four congenital abnormalities:
VSD, pulmonary valve stenosis, a misplaced aorta and a thickened right ventricular wall (right ventricular hypertrophy)
