Difference between revisions of "Vascular Development - Anatomy & Physiology"
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===Vasculogenesis=== | ===Vasculogenesis=== | ||
| − | Vasculogenesis occurs during the third week of gestation in domestic mammals, initially in the yolk sac and afterwards in the allantois. The blood vessels form from blood islands | + | Vasculogenesis occurs during the third week of gestation in domestic mammals, initially in the yolk sac and afterwards in the allantois. The blood vessels form from blood islands containing haemangioblasts which develop from mesodermal cells in the presence of fibroblast growth factor. Exposure to angiopoietin and vascular endothelial growth factor (VEGF) stimulate differentiation of haemangioblasts to angioblasts which ultimately develop into endothelial cells. |
===Angiogenesis=== | ===Angiogenesis=== | ||
The sprouting of new capillaries from existing blood vessels occurs when surrounding cells become hypoxic. A low partial pressure of oxygen causes an increase in levels of hypoxia-inducible factor (HIF), this in turn stimulates cells to release vascular endothelial growth factor (VEGF) leading to new vessel formation. Other growth factors such as angiopoietin also play an important role. Angiopoietin-1 interacts with the Tie-2 receptor on endothelial cells at the sites where sprouting occurs. Platelet derived growth factor (PDGF) and transforming growth factor-β (TGF-β) influence the maturation of the capillary network. Angiopoietin-2 expression in the absence of VEGF leads to vessel regression and apoptosis. | The sprouting of new capillaries from existing blood vessels occurs when surrounding cells become hypoxic. A low partial pressure of oxygen causes an increase in levels of hypoxia-inducible factor (HIF), this in turn stimulates cells to release vascular endothelial growth factor (VEGF) leading to new vessel formation. Other growth factors such as angiopoietin also play an important role. Angiopoietin-1 interacts with the Tie-2 receptor on endothelial cells at the sites where sprouting occurs. Platelet derived growth factor (PDGF) and transforming growth factor-β (TGF-β) influence the maturation of the capillary network. Angiopoietin-2 expression in the absence of VEGF leads to vessel regression and apoptosis. | ||
| + | |||
| + | ===Arteriogenesis=== | ||
Revision as of 15:34, 10 July 2008
Overview of Vascular Development
Blood vessel formation is a combination of the following three processes:
- Vasculogenesis: the formation of blood vessels from endothelial progenitor cells.
- Angiogenesis: the sprouting of new capillaries from pre-existing vessels.
- Arteriogenesis: the remodelling of newly formed or pre-existing vascular channels into larger and more muscular arterioles.
Vasculogenesis
Vasculogenesis occurs during the third week of gestation in domestic mammals, initially in the yolk sac and afterwards in the allantois. The blood vessels form from blood islands containing haemangioblasts which develop from mesodermal cells in the presence of fibroblast growth factor. Exposure to angiopoietin and vascular endothelial growth factor (VEGF) stimulate differentiation of haemangioblasts to angioblasts which ultimately develop into endothelial cells.
Angiogenesis
The sprouting of new capillaries from existing blood vessels occurs when surrounding cells become hypoxic. A low partial pressure of oxygen causes an increase in levels of hypoxia-inducible factor (HIF), this in turn stimulates cells to release vascular endothelial growth factor (VEGF) leading to new vessel formation. Other growth factors such as angiopoietin also play an important role. Angiopoietin-1 interacts with the Tie-2 receptor on endothelial cells at the sites where sprouting occurs. Platelet derived growth factor (PDGF) and transforming growth factor-β (TGF-β) influence the maturation of the capillary network. Angiopoietin-2 expression in the absence of VEGF leads to vessel regression and apoptosis.