Development of the Heart Flashcards
At what embryonic week does the cardiovascular system begin to appear and function?
Week 3-4
Where is the heart originally positioned?
Cranial-most region of embryo; later swings down to lie in the thorax
Label This Diagram; Reproduce this diagram
Describe Process of Heart Folding
1) Myocardiogenesis begins at cranial lateral plate mesoderm with formation of lateral endocardial tubes
2) Lateral folding merges endocardial tubes and brings all cardiogenic mesoderm together
3) Fusing of endocardial tubes forms heart tube
3.1) Heart tube can now be classified into chambers by small sulci
4)Surrounding myocardium engulfs heart tube and forms cardiac jelly
4.1) Heart begins to beat
5) Heart begins to loop
6) Endocardium and early septa begin to form
Label this Diagram
List key concepts of embryonic heart formation per Dr. Williams lecture
1) The heart begins in the cranial-most region and during folding “swings down” to lie in the thorax. The aorta remains posterior to the foregut.
2) The developing tubular heart dilates to form chambers, constricts to demarcate the
transition from the chambers to the outflow system and venous return and then rotates to the adult orientation in the thorax.
**3) Four endocardial cushions form the separation between the atria and ventricles and also contribute to the formation of the mitral and tricuspid valves. **
4) The development of the interatrial septum is complicated because a patency is needed to keep blood flowing during fetal development.
**5) The development of the atrial septum involves the septum primum which is replaced by the septum secundum and the foramen (ostium) primum which is replaced by the foramen (ostium) secundum.
The foramen secundum forms the foramen ovale and is covered by the valve of the foramen ovale. **
**6) Development of the interventricular septum is less complicated and basically involves the upward growth of the interventricular septum. **
7) The aorticopulmonary outflow from the heart is established by the development of conotruncal ridges which wind upward like a spiral staircase completing the pulmonary outflow from the right ventricle and the aortic outflow from the left ventricle.
8) Prenatal Circulation avoids unnecessary flow to organs not yet needed, whereas postnatal circulation establishes necessary flow to organs that are now needed and closure of shunts that could be a
problem if they remained open.
What forms the endocardial cushions which start to separate atria and ventricles?
Migrating Neural Crest Cells
Describe the process of embryonic heart formation
1) Cranial Lateral plate mesoderm initiates vasculogenesis and forms endocardial tubes
2) Lateral body folding brings endocardial tubes towards thorax and merges them together until they fuse
3) Primitive heart tube is formed with sulci slightly demarcating individual chambers
4) Chambers include sinus venousus, primitive atrium, primitive ventricle, bulbous cordis, truncus arteriosus
5) Heart loops
6) Atrioventricular cushions begin to divide atria and ventricles and form mitral/tricuspid valves
7) Septum Primum descends from ceiling - whole before it reaches atrioventricular cushions is called foramen primum (allowing right to left blood flow through atria)
8) Foramen secundum appears at top of septum primum as foramen primum is closing
9) Septum secundum grows from ceiling and overlaps foramen secundum - foramen ovale formed
10) Interventricular septum grows upward and divides R and L ventricles
11) Endocardial cushions grow together and form spiraling conotruncal ridges that turn into pulmonary artery and aorta
12) Three bypasses in heart are formed - ductus arteriosus, foramen ovale, ductus venosus
13) DONE!
What type of cells start the whole heart process? Where do they start and to where do they move?
Angiogenic cell clusters
Start cranially and rotate down to thorax, anterior to esophagus
What are the 5 divisions of the primitive heart tube and what do they eventually turn into?
1) Sinus Venosus - Turns into coronary sinus and part of right atrium
2) Primitive Atrium - Turns into rough parts of atrium
3) Primitive Ventricle - Turns into rough parts of ventricles
4) Bulbuis cordis - Turns into smooth part of ventricles
5) Truncus Arteriosus - aorta and pulmonary trunk
Where do endocardial atrioventricular cushions comes from?
Neural Crest Cells
Describe components of the foramen ovale.
Septum secundum is firm superior wall that does not move
Septum primum acts as the one-way valve to let blood flow from right to left atrium, bypassing the lungs
Foramen primum no longer exists
Foramen secundum is the opening of the foramen ovale
How does the truncus arteriosus lead to pulmonary artery and aorta formation?
Conotruncal ridges fromed from endocardial cushions pushing together wind upward and form pulmonary/aortic tracts.
What is the function of the ductus venosus?
Bypass the liver by connecting the umbilical vein with the inferior vena cava
What is the function of the foramen ovale?
Bypass the lungs - allow flow from right heart to left heart
