Heart Development Flashcards
What does the secondary heart field produce?
- forms right ventricle and outflow tract
- cells of this field are derived from pharyngeal mesoderm and cam form either cardiac or skeletal muscle
- cells express Hand-2 -> absence results in absence of righ ventricle
What does the proepicardium form?
- forms epicardium
- forms interstitial cells and vasculature smooth muscle
- gives rise to coronary vasculature
What forms in late third week? What is it guided by? What are some characteristics?
- primary myocardium
- guided by Tbx-2
- slow growth, slow impulse conduction, slow contraction, ability to undergo spontaneous depolarization
Describe how the cardiac tube loops.
- composed mostly of cells from primary heart field
- incorporates cells from secondary heart field
- undergoes dextran looping
- first asymmetric embryonic structure to appear
- atrial and ventricular chamber bulges appear on outer surface of loop and at inflow end -> chamber myocardium
What is chamber myocardium guided by? What it’s characteristics?
- guided by Tbx-5
- fast growth, high impulse conduction, strong contraction, low ability to undergo spontaneous depolarization
What are some characteristics of early symmetrical heart tube? (Primary myocardium)
- slow growth slow impulse conduction
- slow contraction
- ability to undergo spontaneous depolarization
- development guided by transcription factor Tbx-2
WHat are the characteristics of the chamber asymmetrical heart tube?
- bulges representing the ventricular and atrial chambers appear as the heart tube loops
- development of ventricular chamber guided by TF Tbx-5
- high proliferative capacity
- high conduction velocity
- low capacity to generate spontaneous impulses
What is the result of cardiac looping?
- S shaped heart
- original caudal inflow part (atrium) is now dorsal to outflow part of heart
- outflow part of heart = bulbus cordis, leads to aortic sac and aortic arch system
- internal septum begins to divide ventricle
- later an internal septum will begin to divide antrum
What are the different parts of the bulbus cordis?
- broader proximal part of bulbus cordis -> conus arteriosus
- narrower distal part of bulbus cordis -> truncus arteriosus
What is the AV partitioning derived from?
- derived from thickening of cardiac jelly
- endocardial cells transform into mesenchymal cells and migrate into the existing cardiac jelly
What thickening so form for the AV septum?
- AV cushions
- endocardial cushions
What are the AV cushions?
-two cushions meet in middle and form two channels between the single atrium and the single ventricle
-these early cushions serve as primitive valves but probably do not contribute to the final valves
_final valves come from endocardial invaginations
What are primary heart fields?
- aka heart crescent
- forms left ventricle and the atria
- most primitive component of the mammalian heart
-more anterior cells are not exposed to TA and assume the default ventricular identity
+cells here express Hand-1, absence results in defective left ventricle
-more posterior cells are exposed to high gradient of RA and assume an atrial identity
When does atrial partitioning happen?
-during 5th week
What are the components of the atrial partition?
- interatrial septum primum
- interatrial septum secundum
How does the interatrial septum primum grow?
- downward growth from cephalic wall of single atrium to endocardial cushion
- separates the atrium into left and right chambers
How does the septum secundum form?
-forms to the right of the septum primum and grows from dorsal to the ventral part of the atrium
What the three openings in the atrial wall?
- interatrial foramen primum
- interatrial foramen secundum
- foramen ovale
What is the interatrial foramen primum?
- space between the leading edge of septum primum and the endocardial cushion
- right to left atrial shunt
What is the interatrial secundum?
- forms at the cephalic end of the septum primum through apoptosis
- continues the right to left atrial shunt after the foramen primum closes with the fusion of the septum primum with the endocardial cushion
What is the foramen ovale?
- space formed within the septum secundum
- right to left atrial shunt
When does ventricle partitioning begin?
-during the fifth week
What are the components of the ventricular partition?
- thick interventricular septum growing from apex of ventricular loop toward atrial endocardial cushions
- interventricular foramen
What is the interventricular foramen?
- transitory opening between the future right ventricle and the future left ventricle
- becomes obliterated as the septum fuses with the endocardial cushions
What is the outflow tract initially made of?
-bulbus cordis
+divided into the conus arteriosus and the truncus arteriosus
- proximal region (conus) is derived from secondary heart field
- distal region (truncus) is derived from neural crest
How does the outflow tract partition form?-
- partitioning begins with growth of two opposing truncoconal ridges into the lumen
- ridges meet in the middle ad completely divide the lumen into two separate passageways
- the final septum forms a spiral path which V creates the spiral pattern of the ascending aorta with the pulmonary trunk in the final heart pattern
