Untitled Flashcembryo lab

00:00:01 - 00:01:20 as a normal part of growth and development the body must generate new blood vessels to oxygenate the tissues in a process called angiogenesis new vessels Sprout from existing ones in this movie we see endothelial cells sprouting to form new branches from the aorta of a zebra fish embryo each Sprout is initially formed by one or a few endothelial cells the process begins when an endothelial cell of a small vessel is activated by an angiogenic stimulus such as vascular endothelial growth factor or 00:00:40 - 00:02:03 vegf in response to the stimulus the endothelial cell becomes motile and extends filopodia that guide the development of a capillary Sprout the leading or tip cell continues to move away from the capillary as cells behind it migrate in and divide forming a stalk the Sprout begins to hollow out forming a tube in this process penic vesicles fuse with one another the large vacul formed in this way then fuse with one another creating a lumen that runs through the capillary sprout in culture endothelial cells 00:01:22 - 00:02:41 behave in a similar way they spontaneously develop internal vaces that join up from cell to cell creating a single Lage shared by many cells in the example shown here the individual cells contain either a red or a green fluorophor note that the areas of green and red are distinct even those cells share alumin they do not share cytoplasm and remain separate cells after the fusion events angiogenesis is critical not only in normal development and wound healing but also in the development of tumors a tumor must stimulate blood 00:02:05 - 00:03:19 vessel formation to grow more than a few millimeters in size VF is a key activator of angiogenesis in both normal cells and tumors when cells within a tumor become oxygen deficient they begin to express VF VF diffuses through the tissues activating endothelial cells on nearby vessels this results in capillary sprouting some new cancer therapies are targeted to block the action of Vega with varying clinical results [Music] [Music]

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Hey, I'm Maisie. I'll tell you about vascular genesis. Vascular genesis, you know, is the denovo formation of blood vessels. So, let us dive in and explore more about this incredibly important process. Now, the cardiovascular system begins to form at about the third week of embryo development. So, let's start with a quick quiz. Do you remember the three gem layers? That's right. These are the outer ectom, this outer one, endoderm, the innermost, and the messoderm, which lies in the middle. Good job. Keep in mind that above the ectom is the amniotic cavity and below the endodm is the yolk sack. This is the neural tube and this one is the motor cord. Now do you have any idea which germ layer gives rise to the blood vessels? You got it. The messoderm. Well, the meoderm has three parts. The paxial meoderm that lies just on the sides of the neural tube and gives rise to summits. The intermediate messoderm as the name is suggesting that it is located between the paxial and the lateral plate messoderm develops into vital parts of the eurogenital system like kidneys, gonads and respective tracts and the lateral plate meoderm found at the periphery of the embryo. Now the lateral plate messoderm develops the cavities that fuse together to form an intrambbriionic cavity or intra embriionic zumm. What this cavity does is that it splits the lateral plate messoderm into two layers. The outer one that adheres to the ectoaderm is referred to as the somatic layer or parietal layer also known as the somatapur. And the inner layer that adheres to the endodm is referred to as the splanknic layer or visceral layer known as the splanknip. Now the question is that which layer is responsible for giving rise to the blood vessels? Any guesses? Yes, it is the splanknic layer. Also I forgot to mention that this part of meoderm left is known as extra embriionic meoderm. Now some sort of growth factors called the fibroblast growth factor 2 or FGF2 calls them enkimal cells of the splanknic layer to proliferate and differentiate to form some cells that are known as hemangi blasts. You can see that the word hemangio blasts consist of three words hem angio and blasts. Hem means blood. Angio means vessels and blasts means to form. So it is obvious that he blasts are the cells that will form blood vessels and the primitive blood cells. Now as development progresses the peripheral hemangi blasts are differentiated into angiolasts which are the precursor cells for endothelial cells that build the blood vessels. Well, these angoblasts form clusters. These clusters of angiolasts make up the blood islands in the extra embriionic meoderm. Blood islands. What a cool name though. Anyways, these blood islands are also known as pandas islands or wolf's islands. And the hemangia blasts in the center of blood islands form primitive hematopoetic stem cells or HSC for short that are the precursors of all blood cells including red blood cells, white blood cells and platelets. Now what happens next is that these endothelial precursor cells of neighboring blood islands rearrange themselves on the extra embriionic meoderm and merge the lumens of these blood islands which becomes the primitive vascular system forming the primary vascular plexus. So this whole process is what we refer to as the vascular genesis. Now once the primary vascular plexus is formed, rest of the blood vessels are formed by the sprouting from existing vessels or angioenesis that I will be discussing in the very next video. Hey, I'm getting a feeling that you might have a question on your mind right now. Am I right? Well, let me guess. You're wondering if blood vessel formation only happens during embryionic development, right? Actually, that's not entirely true. While it's mostly angioenesis that creates new blood vessels in adults, there are some very rare cases where vascular genesis can occur in certain tissues under certain conditions. Well, we have circulating endothelial progenitor cells that are actually the derivatives of stem cells. These cells contribute to the vascular genesis in adults. Examples of where vascular genesis can occur in adults a tumor growth, revascularization or neovascularization after trauma. For example, after cardiac eskeeia or retinal eskemia, endometriosis. It appears that up to 37% of the microvascular endothelium of the ectopic endometrial tissue originates from endothelial progenitor cells.