Flashcards in Heart Development Deck (26)
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 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?
-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
-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?
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
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
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?
+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