Primary hemostasis | Advanced hematologic system physiology | Health & Medicine | Khan Academy

During primary hemostasis, a platelet plug is formed to rapidly stop the initial bleeding after injury. Learn about the different steps involved in primary hemostasis: vasoconstriction, platelet adhesion, activation and degranulation, platelet aggregation. Created by Gricelda Gomez.

Health & Medicine on Khan Academy: No organ quite symbolizes love like the heart. One reason may be that your heart helps you live, by moving ~5 liters (1.3 gallons) of blood through almost 100,000 kilometers (62,000 miles) of blood vessels every single minute! It has to do this all day, everyday, without ever taking a vacation! Now that is true love. Learn about how the heart works, how blood flows through the heart, where the blood goes after it leaves the heart, and what your heart is doing when it makes the sound “Lub Dub.”

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[MonnieMoo]

THIS VIDEO IS ABSOLUTELY AMAZING!!!! I actually am understanding!! :D THANK YOU KHAN ACADEMY!! :D

[majedsaeedy]

Amazing explanation, clear and informative diagrams. I was watching a lecture at my university and didn't really understand primary hemostasis, but this video really cleared it up.

[LD-jpiu]

Great explanation. Really helped explain the details of primary hemostasis from First Aid 2017

[jmoney]

I don't know why people are complaining about the voice over. I thought it was perfect. She was talking like an actual person does when they are talking to you. And personally, that helps me listen better.
Would people rather it be completely monotone? To each their own I suppose.

[胡馨-yh]

thank you khan academy, for helping me with almost every exam TT

[demonskwirl]

this is outstanding. very concise, understandable, easy to remember

[mikeearls]

its cool to learn here definitely....but the high speed video and high speed talking of a person who knows everything about the topic makes learning harder (have to constantly stop video) teaching is not just spewing out stuff as fast has humanly possible....but actually considering who is watching....of course IMHO

[michaelgilman]

Thanks pretty darn good overview. My Lippincott Pharmacology text fills in some details but your narration and illustration make the concepts and substances a bit easier to latch on to...One small note of criticism, meant constructively, the "hole" in the vessel is called the lumen.

[mandisangema]

You saying fibrinogen leads to platelet aggregation? Doesnt have to be cleaved to fibrin by thrombin first?

[minhlucnguyen]

Thank you so much for blowing up my mind, this video is super amazing and easy to be understood!!!!

[Z]

thank you! very helpful video, i recommend also watching the 2ndary hemostasis video by Khan Academy

[rubaali]

I can be clear with u guys I wouldn't make it through one day before exam without u 😭🙏

[kv]

thank you for your sharing ms, this is best, i really analyze the process of primary hemostasis, thank you, i hope for you response 😇

[priyankamidha]

Thank you so much, amazing video. I have a question if someone can help me with it -
When an injury occurs, why do we only lose NO and prostacyclin (vasodilators) with the blood and not the vasoconstrictor, endothelin?

[alexcoreablecoreable]

for the last part of this video, isn't it fibrin instead of fibrinogen? i thought fibrinogen needs to be converted to fibrin and then it can form cross-linked mesh?

[blackyrocky]

First response to vascular injury is vascular spasm or vasoconstriction to reduce bleeding. Then platelet plug, aggregation, and thrombus form. Injured or damaged endothelial cells release endothelin which will act on smooth muscles to contract and ultimate goal will be vascular spasm. Particularly endothelin will trigger release of calcium in smooth muscles which will cause contraction

[rahmiaziza]

this is really helpful!
thanks a lot 😊