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Embryology Exam III > Heart Development > Flashcards

Flashcards in Heart Development Deck (26)
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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