Heart Development Flashcards
Define vasculogenesis
-de novo creation of blood vessels directly from mesenchyme
When does extraembryonic vasculogenesis begin?
around day 17
True or False: extraembryonic vasculogenesis is coupled with hematopoeisis
True
What are hemangioblasts?
progenitor cells of extraembryonic vasculogenesis that can give rise to the hematopoietic lineage or to endothelial cells
True of False: intraembryonic vasculogenesis is couple with hematopoeisis
False
When does intraembryonic vasculogenesis begin?
around day 18
What are angioblasts?
a subset of cells in the intraembryonic splanchnic mesoderm that differentiate directly into endothelial precursor cells
Define angiogenesis
budding or sprouting of new vessels from existing ones
Define intussusception
splitting a blood vessels in half to make two vessels
How does angiogenesis happen?
- tip cells “invade”
- stalk cells follow
- endothelial cells proliferate and migrate
Where do embryonic hematopoietic stem cells reside and by what day of development do they reach there?
in the primordial liver
by Day 23
What types of cells can embryonic hematopoietic stem cells become?
erythrocytes, macrophages, and megakaryocytes
What are definitive hematopoietic stem cells?
cells that can create the full range of myeloid and lymphoid lineages
What specialized cells come out of the AGM (aortic-gonadal-mesonephric) region of the dorsal aorta?
hemogenic endothelial cells
From the AGM, where do hemogenic endothelial cells go?
they seed the liver by day 30
What do the hemogenic endothelial cells do when they get to the liver?
cell-cell interactions with embryonic hematopoietic stem cells
give the stem cells the full capacity to generate both myeloid and lymphoid lineages
Where do the definitive hematopoietic stem cells go after their transformation in the liver
lymph organs
bone marrow
What are the mechanisms by which the vascular plexus expands?
sprouting
intussusception
cont’d proliferation of EPC’s
recruitment of new mesoderm into the walls of existing vessels
Pathology: Angiomas
-abnormal blood vessel and lymphatic capillary growth via vasculogenesis
What is the likely cause of angiomas?
abnormal levels of angiogenic factors
What are the two types of angiomas?
Capillary Angioma = excessive growth of a small capillary network
Cavernous Angioma = excessive growth of venous sinuses
Pathology: Hemangiomas of Infancy
- benign tumors made mostly of endothelial cells
- most regress on their own
-depending on site or degree, can lead to clinical complications
What germ layer gives rise to early cardiogenic precursors?
intraembryonic splanchnic mesoderm
has neural crest contributions
What do neural crest cells do in the development of the heart?
- regulate the activity of the 2nd heart field
- play a role in the separation of the outflow tracts into pulmonary A. and aorta (cushion tissue derived from neural crest cells)
What are some roles of endoderm during heart development?
- signals the development of early blood vessels
- signals the formation of early endocardium from splanchnic mesoderm
What is the role of endoderm in regards to cardiac looping?
-signaling continual proliferation of splanchnic mesoderm (second heart field) necessary for driving cardiac looping
Delineate the process of forming a single cardiac tube from two primitive heart tubes.
- sides of embryo move toward midline and ventrally
- endocardial tubes are brought together and fuse
- adjacent cardiogenic mesoderm is incorporated
- tube sinks into the pericardial cavity
List the layers of the heart tube from superficial to deep.
- myocardium
- cardiac jelly
- endocardium
What is myocardium?
mesoderm adjacent to the endocardial tubes
What is cardiac jelly?
concentration of ECM b/w endocardium and myocardium
What is endocardium?
inner epithelium continuous with blood vessels
Delineate the formation of endocardium.
mesodermal precursors
specialization of endothelial cells
endocardium
From what germ layer is endocardium derived?
intraembryonic splanchnic mesoderm
What is the first heart field (cardiac crescent)?
formation of endothelial precursor cells in clusters, plus the adjacent mesoderm
-in a horseshoe shape within a cardiogenic area of intraembryonic splanchnic mesoderm