1.3 Heart Development Flashcards
When are cardiac tissue cells defines?
During gastrulation cells of the primary heart field are specified
What happens to the primary heart field during development?
Divides into first and second heart fields (based on times of cell differentiation)
What structures develop from the first heart field?
L and R ventricles
What structures develop from the second heart field?
R ventricle and Outflow tract
How is the primitive heart tube formed?
Precursor cells from FHF differentiate
Two sides of heart zip together to form heart tube
How does the straight heart tube form a four chambered heart?
Early looping - ventricle pushed down, atrium pushed up to form loop
Late looping - atrium pushed to top, ventricle pushed to bottom
Atrium divided into two (L and R), wedging
Ventricle divided into two (L and R), septation
What is the alignment of atria and ventricles dependent on?
Dependent upon formation of endocardial cushions
Fuse to define left and right AV canals
What are endocardial cushions made from?
Made from matrix jelly
Become populated by mesenchymal cells derived from endocardium
What do the endocardial cushions give rise to in the developing heart?
Give rise to heart valves
What is responsible for the division between left and right atria?
Septum primum grows down to divide L and R
Septum secundum grows down immediately adjacent
Why is ostium primum important?
Initially allows communication between the two atria
What is ostium secundum and when does it form?
Second ‘hole’ which forms after ostium primum closes
Allows continued communication between the two atria
What is the difference between septum primum and septum secundum?
Septum primum is formed first
Septum secundum doesn’t grow down to reach and fuse with the AV cushion
How are the ventricles separated?
Septated by the growth of muscular septum with mesenchymal cap (cap forced into contact with AV tissue and sill fuse)
What is the final event in heart development?
Septation of OFT into aortic and pulmonary trunks to create dual circulation
What causes the septation of the OFT?
OFT endocardial cushions that develop in same way as AV canal but neural crest cells responsible for OFT into aortic and pulmonary trunk
How many aortic arches are there, and how many remain throughout development?
6
Aortic arches 1,2,5 do not fully form so are lost
What does the 3rd aortic arch give rise to?
Left and right carotid arteries
What does the 4th aortic arch give rise to?
Aorta
Right subclavian artery
What does the 6th aortic arch give rise to?
Left and right pulmonary arteries
Ductus arteriosus
Why does the foetus develop shunts?
Organs require some blood for development but still fragile so too much blood is harmful
Name the major shunts and openings to restrict blood flow to the liver and lungs.
Ductus venosus
Ductus arteriosus
Foramen ovale (Ostium secundum)
What is the Ductus Venosus?
Blood vessel which connects umbilical vein to the inferior vena cava
What is the Ductus Arteriosus?
Blood vessel connecting the pulmonary trunk to descending aorta
What is the Foramen Ovale?
Opening that connects Right to Left Atrium
