Embryonic Development Of The Heart Flashcards
What are the blood islands?
Zones within the mesoderm with the capacity to produce the whole CVS
How does folding create the primitive heart tube?
It causes the blood islands to fuse together
What are the different parts of the primitive heart tube?
Aortic roots Truncus arteriosus Bulbus cordis Ventricle Atrium Sinus venosus
What does the mature left atrium develop from?
A small portion of the primitive atrium
Proximal pulmonary veins
What does the right atrium develop from?
Most of the primitive atrium
Sinus venosus
What is cardiac looping?
Tube elongates
Runs out of room due to pericardium
Twists and folds up- regular and predictable
This places the inflow and outflow in the correct orientation with respect to each other
This allows cardiac septation to occur normally
How does septation of the outflow tract occur?
PA and Aorta are originally one vessel (truncus arteriosus)
Endocardial cushions appear inside it
As they grow towards each other they twist around each other and form a spiral septum
How is the foramen ovale built?
Why is it needed?
Septum primum grows from top of heart to endocardial cushion leaving a small hole called the osteum primum
As the osteum primum dissappears the osteum secundum appears further up
The septum secundum then grows down from the roof of the primitive atria. This then leaves a small hole which together with the osteum secundum forms the foramen ovale
This allows a R to L shunt to bypass the lungs in utero
How is the foramen ovale closed?
At birth when the baby takes it first breath the pressure in the LA exceeds pressure of the RA and septum primum is pressed against septum secundum
What are the two components of the ventricular septum?
Muscular and membranous
How is the majority of the ventricular septum formed?
Muscular portion forms most of septum and grows towards the fused endocardial cushions
A small gap is left and this is called the interventricular foramen
How is the membranous portion of the interventricular septum formed?
Membranous portion of the interventricular septum formed from CT derived from endocardial cushions to fill the gap
What is a ventricular septal defect?
When the membranous portion of the interventricular septum fails to form
Development of the aortic arches
Begins as a bilaterally symmetrical system of arched vessels which undergoes extensive remodelling to create the major arteries leaving the heart
What is the ductus arteriosus?
A channel formed between the arch of the aorta and the pulmonary artery. During fetal life aortic pressure is lower than pulmonary artery so blood moves from pulmonary circulation to systemic circulation
