9.1 Flashcards
(36 cards)
What is angiogenesis?
Formation of new capillaries from existing blood vessels.
What does angiogenesis involve?
Migration and proliferation of endothelial cells.
What are physiological examples of angiogenesis?
Wound healing and menstruation.
What are pathological examples of angiogenesis?
Cancer and rheumatoid arthritis.
What is vasculogenesis?
De novo formation of blood vessels from angioblasts.
Where does vasculogenesis occur?
Extraembryonic and intraembryonic tissues of the embryo.
What is the hemangioblast?
A precursor cell to both angioblasts and hematopoietic stem cells.
What do angioblasts differentiate into?
Endothelial cells.
What is the sequence of vascular development?
Vasculogenesis → primitive vascular plexus → angiogenesis (remodelling and expansion).
What are the two main types of angiogenesis?
Sprouting angiogenesis and intussusceptive angiogenesis.
What initiates sprouting angiogenesis?
Hypoxia-induced secretion of VEGF-A by organ cells.
What are endothelial tip cells?
Cells exposed to the highest VEGF-A; guide the sprout by extending filopodia.
What do stalk cells do?
Proliferate and elongate the sprout.
What happens after sprouts meet?
Tip cells fuse and form a lumen.
How is the new vessel stabilised?
Pericyte recruitment and ECM deposition.
What receptor is highly expressed on tip cells?
VEGFR2.
How is VEGFR2 expression regulated in stalk cells?
Delta-Notch signalling reduces VEGFR2 expression in stalk cells.
What does DLL4 do?
DLL4 (Delta-like ligand) binds Notch on neighbouring cells, reducing VEGFR2.
What is intussusceptive angiogenesis?
Splitting of existing vessels by inserting tissue columns into the lumen.
Is VEGF gradient required?
Intussespective
No – all endothelial cells respond similarly.
What structures form during intussusception?
Endothelial pillars that fuse and split the vessel longitudinally.
What are key differences between sprouting and intussusception?
Sprouting = tip/stalk cell dynamic, VEGF gradient; Intussusception = fast, no VEGF gradient, structural remodelling.
What triggers angiogenesis in hypoxia?
Low oxygen stimulates VEGF and capillary growth.
How does metabolic rate relate to angiogenesis?
High metabolism → low O₂ → promotes angiogenesis.
