Cardio Development Flashcards
When do embryonic blood vessels and heart start to develop? Where do they form?
- 18 days of development
- form in splanchnic layer of the extaembryonic mesoderm (angioblasts)
Vasculogenesis in yolk sac?
- mesenchymal cells differentiate into endothelial precursor cells, angioblasts, which aggregate to form blood islands
- contain pluripotent hematopoietic stem cells - small cavities begin to appear and angioblasts form endothelial cell lining
- cavities fuse to form channels
Angiogenesis in yolk sac?
- branching or sprouting of new blood vessels from pre-existing ones
- they connect to the primitive heart tube that is forming simultaneously
Why does vasculogenesis and angiogenesis occur at this stage in the embryo?
-simple diffusion of nutrients across the placenta is no longer sufficient to support the growing embryo
What is the first sign of gastrulation?
primitive streak in epiblast
Where does the pericardiac mesoderm derive from?
epiblast
Outflow tract in relation to inflow tract in the primitive streak?
-outflow pass through primitive streak more cranially
Where do cells giving rise to the ventricles pass through the streak?
mid region
Precardiac mesoderm derived from?
-once pericardiac cells go through the streak they migrate as part of the splanchnic mesoderm to form a region in the anterior half of the embryo
What does the precardiac mesoderm become?
tubular heart during embryonic folding
What is the first step in the formation of the heart?
appearance of bilateral, parallel endocardial tubes that form by vasculogenesis in rostral splanchnic mesoderm
When and where does the bilateral cardiac tubes fuse (embryonic folding)?
along the midline of the embryos when the embryo folds in the cranial to caudal and lateral directions
How do bilateral endocardial tubes fuse?
-by ventral flexure of the head fold and ventral convergence of the lateral body folds
What do the bilateral endocardial tubes become?
-they fuse at the midline to form a single endocardial tube that is surround by myocardium
What separates the endocardium and myocardium?
cardiac jelly
What forms next after fusion of the endocardial tubes?
formation of 3 layers:
- endocardium
- myocardium
- epicardium
Where does the epicardium come from?
migration of epithelial and mesenchymal cells on surface of myocardium
When does the primitive heart tube loop form?
- between 21-28 days
- after fusion of bilateral endocardial tubes
What shape does the primitive heart tube loop form? why?
S
-to allow segmentation into different chambers
Outflow vs inflow tract direction after heart tube loops?
OFT: dextrocaudally
-ventricular segment
IFT: dorsocranially
-great veins to enter heart
Primary heart field?
- inflow segment
- left ventricle
- half of right ventricle
Secondary heart field?
- outflow
- half of right ventricle
Third heart field?
Proepicardium
-progenitor to epicardium, coronary vessels, and cardiac fibroblasts
Fourth heart field?
Cardiac neural crest
What are the 5 core transcription factors that commit to cardiac lineage?
- NKX-2
- MEF-2
- GATA
- Hand
- Tbx
How do Cushions form?
convergence of endocardial prominences at AV border and Contruncus through endocardial mesenchymal transition (EndMT)
What do Cushions separate?
- atria and ventricles (dorsal and ventral)
2. aortic and pulmonary trunks of outflow tract Conotruncus
What will be the future AV valves?
-when dorsal and ventral cushions bulge into lumen but retain openings on both sides
When do partitioning of the atria and ventricles take place?
-occur simulaneously during 4th-8th weeks of gestation
Septum primum?
-divides right and left atria
Foramen primum?
- opening in membrane of septum primum
- shunts oxygenated blood from right to left atria
Cardiac septation steps at 28 days?
- Septum primum grows from dorsal wall toward AV cushions
- Foramen primum shunts oxygenated blood from right to left atria
- Muscular inter ventricular septum grows toward AV cushions and bulbar ridge
- Dorsal cushion forming
Cardiac separation steps 32-35 days?
- septum primum fuses with AV cushions to obliterate the foramen primum
- perforations in septum primum coalesce to form the foramen secundum
- foramen secundum grows
- Muscular IV septum grows
- Membranous IV septum begins to form
Cardiac septation 5-8 weeks?
- septum secundum grows and overlaps foramen secundum in septum primum leaving foramen ovale
- inferior remnant of septum primum forms valve of foramen ovale
- foramen ovale permits shunting of oxygenated blood from right to left atria
What forms the bulbar and truncal ridges?
-active proliferation of mesenchymal cells in the walls of the bulbus cordis and truncus arteriosus
Where is ridge mesenchyme derived from?
-endocardium via epithelial mesenchymal transition and neural crest cells
Where do cardiac neural crest cells migrate to to from the ridges?
through PA 3, 4, 6 to form bulbar and truncal ridges
What do the ridges create when they fuse together?
undergo 180 degree spiral to form aorticopulmonary septum
what does the aorticopulmonary septum divide?
divides the Bulbis cordis and truncus into two arterial channels, Aorta and Pulmonary trunk
What does the bulbus cordis become?
- becomes incorporated into walls of ventricles
- right: becomes conus arteriosus (infundibulum) to form pulmonary trunk
- left: forms walls of aortic vestibule inferior to aortic valve
When do semilunar valves form?
when partitioning of truncus is complete
