Lecture 19 : Angiogenesis Role of VEGF and Hypoxia Flashcards
What is Vasculogenesis?
Vasculogenesis is the embryonic formation of endothelial cells from the mesoderm layer precursors to form new blood vessels in blood islands.
What does Vasculogenesis give rise to?
Vasculogenesis give rise to the heart and the first primitive vascular plexus inside the embryo and in its surrounding membranes.
Vasculogenesis is …?
Embryonic
What happens during Vasculogenesis?
During Vasculogenesis,
- Blood vessel formation first occurs in the wall of the yolk sac (Figure A)
- Undifferentiated mesenchyme cells condense to form Angiogenetic cell clusters (Figure B)
- These centers of Angiogenetic cell clusters (Figure B) form the blood cells form the primitive blood cells (Figure C)
- The outsides of the Angiogenetic Cell Clusters develop into blood vessel Endothelial Cells
Where do Vascular development in the embryo and extra-embryonic membranes occur?
The Vascular System form in two specific sites in the embryo:
- One in the blood islands of the yolk sac
- The other in the embryo proper
What is Angiogenesis
Angiogenesis is the process by which new blood vessels from pre-existing vessels that are formed in the early stages of vasculogenesis.
What are the two stages of Angiogenesis?
- Sprouting Angiogenesis
- Intussusceptive Angiogenesis
What is Sprouting Angiogenesis?
Sprouting Angiogenesis is when tissues that have low nutrient and oxygen supply will produce signals (VEGF-A) that induces endothelial cells to secrete proteases that degrade their basement membranes and allow the endothelial cells to escape their original vessel walls.
These cells continue to proliferate and form sprouts connecting neighboring vessels, guided by extending towards the source of the angiogenic signal.
- Basically… Low Oxygen and Nutrients produces VEGF-A signals
- VEGF-A signals induce endothelial cells to secrete proteases to disintegrate (degrade) their basement membranes and run away.
- This is done so the endothelial cells can escape from their original vessel walls.
- These same runaway endothelial cells will keep making copes if themselves and make sprouts that connect to neighboring vessels.
- They’re running towards the source of the angiogenic signal.
- The sprouts that these runaway endothelial cells are making that connect them to their neighbor vessels are all done while they’re following the origin of that angiogenic signal
- They’re running towards the source of the angiogenic signal.
What is Intussusceptive Angiogenesis?
Intussusceptive Angiogenesis is also known as splitting angiogenesis, which is the formation of new vessels by splitting a pre-existing vessel in two.
Basically…
- Making a new blood vessel by splitting an existing blood vessel into two.
- Turning one existing blood vessel into two blood vessels ~~~~~
What is Happening in the Diagram?
Angiogenesis is happening,
Angiogenesis is the formation of new blood vessels from existing blood vessels,
Can be either:
- Sprouting Angiogenesis
- or
- Inusscepetive Angiogenesis
What are examples of Angiogenesis in Adults?
Angiogenesis in the uterine lining,
- In Women, Angiogenesis happens each month for a few days in the lining of their uterus.
- This happens during their Menstrual Cycle
- New blood vessels are formed from their existing ones (Angiogenesis)
Angiogenesis in tissue during wound healing,
- Angiogenesis happens in our tissue when we get hurt,
- New blood vessels are made from existing ones (Angiogenesis) to heal our tissue when we get hurt.
Explain this Slide
Not sure if this slide is super important
- The largest blood vessels are Arteries and Veins
- Arteries have Veins have a thick layer of connective tissue and many smooth muscle cells
- Arteries and Veins will have varying thicknesses depending on the diameter and function of those vessels.
-
Blood vessel interiors are only made from a single layer of endothelial cells.
- This single layer of endothelial cells is attached to and separated from the other layers of the basal lamina.
- The finest branches of the vascular system are the capillaries and sinusoids.
- These are composed of endothelial cells and a basal lamina put together with a few perictytes.
- Members of the connective-tissue family
- related to vascular smooth muscle cells
- Pericytes wrap themselves around the small vessels that have other important functions
What are the different Characteristics of Arteries, Veins, and Capillaries?
….Capillaries are the smallest of these blood vessels
Describe Capilaries
Capillaries are:
- very thing
- composed of a single layer of endothelial cells
- can be:
- continuous
- Fenestrated
- Sinusoid
- Have incomplete basement membrane
What’s the hardest part of the binding process of Oxygen to Tissue?
Binding the first oxygen is the hardest step, one the first one binds, the others will bind more easily.
Check this again, slide 15
What is pO2?
pO2 is a measure of how much O2 is dissolved in the blood.