Heart Development (Brauer) Flashcards
Where and when does hematopoiesis begin?
Day 17 in extraembryonic splanchnic mesoderm adjacent to the endoderm of the yolk sac wall
List the sites of hematopoiesis
- Yolk sac mesoderm
- Primordia Liver
- Aortic Gonadal Mesonephric (AGM) region of dorsal aorta
- Liver
- Lymph organs and bone marrow
What do hemagioblast differentiate into
- Hematopoietic progenitor cells
- Endothelial precursor cells (EPCs)
What is the fate of Hematopoietic progenitor/embryonic cells
By day 23 they populate the primordia liver and generate embryonic erythrocytes, macrophages and megakaryocytes
Where do definitive hematopoietic stem cells arise
From hemogenic endothelial cells of the dorsal aorta in the aortic-gonadal-mesonephric (AGM) region
What is the fate of definitive hematopoietic stem cells
They populate the liver by day 30 and are able to produce the entire hematopoietic cell lineage and lymphoid stem cell lineages. They then go on to populate the lymph organs and bone marrow
Differentiate between vasculogenesis, angiogenesis & intussusception
Vasculogenesis: Mesoderm cells differentiate and form blood vessels DE NOVO
Angiogenesis: Forming of new blood vessels from pre-existing blood vessels
Intussusception: Subset of angiogenesis that involves the splitting of a pre-existing blood vessel in half
Is Intraembryonic vasculogenesis coupled with hematopoiesis?
No, except for the AGM region.
Blood vessel formation within the embryo is not couples with hematopoiesis.
With intraembryonic vasculogenesis, what does the splanchnic mesoderm differentiate into?
Endothelial precursor cells (aka angioblasts)
How does the vascular plexus of the embryo expand
1) Continue to proliferate as EPC
2) Angiogenesis: make new blood vessels from existing ones
3) Intussusception: splitting of blood vessels
4) Recruitment of new mesodermal cells into walls of existing vessels
What are angiomas?
What are the 2 types learned in lecture?
Abnormal blood vessels and lymphatic growth via vasculogenesis.
Capillary hemangioma: Excessive growth of small capillary network
Cavernous hemangioma: Excessive growth of venous sinuses
On day 19, the first heart field or cardiac crest forms. What comprises this?
EPC clusters from intraembryonic splanchnic mesoderm + Adjacent mesoderm that are recruited to form precardial myocytes
How does the single cardiac tube form?
EPCs differenetiate into endothelial cells forming two primitive endocardial tubes. Due to body folding, they fuse and together with the adjacent mesoderm form a simple tubular heart.
From where does the primitive tubular heart dangle from?
Dorsal mesocardium
What does the primary heart tube consist of
Endocardium: Inner epithelium cells continuous with blood vessels
Myocardium: Outer layer of cells
Cardiac Jelly: extracellular matrix btw the endocardium and myocardium
Why does the dorsal mesocardium eventually have to rupture?
To allow the heart to loop
What happens to the remnants of dorsal mesocardium?
Forms the proepicardial organ which consist of cells that migrate over the entire heart to form the epicardium
What happens to the atrium when cardiac looping begins?
Moves cranially and dorsally
What is the function of the conus arteriosus?
Proximal outflow of both ventricles -Is divided so blood from LV and RV go out different vessels
What is the function of truncus arteriosus?
Distal outflow tract
What does the truncus arteriosus eventually become?
Aorta Pulmonary Artery
Describe the second heart field.
Initially inhibited due to its proximity to notochord. After body folding, it is farther away and can start proliferating by adding cells to both ends of the primitive heart tube. -drives cardiac looping
What is the role of neural crest cells in terms of cardiac looping?
-Regulates FGF 8 and drives growth of cells in primitive heart -Maintains cardiogenic mesoderm proliferation and proper myocardial cell specification within the second heart field -Plays important role in regulating cardiac looping