Blood II

How do we make blood clots?

  • endothelial cells form the blood vessels. they each have nuclei.

  • blood moves along blood vessels, carrying oxygen,

  • if a blood vessel gets damaged, blood will rush out and we will lose blood.

    • the platelet is a tiny piece of a cell that your body uses to block up holes suchas a hole in a blood vessel. they stick together and clog holes to prevent blood lose.

  • why arent platelets clump in the blood vessel and not just in damaged parts of the vessel? because the environment in the blood vessel is different than the outside. the outside has collagen, which chemically interacts with platelets and causes them to stick together.

  • fibrin is a protein that tries to strengehten platelet plug by forming mesh of protein that holds the platelts together in fibrin strands. subunits in fribrin strands like to stick together in lines. fibrinogen circulates in blood.

  • fibrinogen is the same as fibrin except it has a piece that doesn’t allow it to stick to itself. fibrinogen is turned into fibrin only at the damaged site. tissue factor proteins outside endothelial cells in wound cause fibrinogen to turn into fibrin.

    coagulation cascade

    1. platelets deposit and form initial plug in wound

    2. to solidify plug, fibrin strands act as a mesh to hold platelet plug together

      1. fibrin(1) molecules are made of fibrin subunits that naturally form a polymer/fibrin strand.

      2. fibrin doesn’t circulate in blood, fibrinogen does. the extra piece on fibrinogen stops the fibrin from sticking from itself.

      3. new proteins released when injured eventually tell fibrinogen to convert into fibrin.

      4. thrombin (2) is activated from an inactive form called prothrombin that has a pice that prevents it from working.

12 ,11 ,9+8 ,10+5 , 2, 1

12→11→9,8→10,5 : intrinsic pathway that gets most of coagulation done

the arrows are more about catalyzing than converting.

3(TF)→7→10 : extrinsic pathway is the spark that gets activated by original injury

  • TF activates 7, which activates a bit of 10, which activates a bit of thrombn, which starts the intrinsic pathway by activating 5,7,8,11,13

fibrin molecules form strands, then they are connected together with cross links. this is enabled by factor 13. 12 is not totally necessary in intrinsic pathway.


thrombin creates plasmin from plasminogen. plasmin acts on mesh networks of fbrin and breaks them apart. thrombiiin stimulates production of anti thrombin. antithrombin decreases amount of thrombin produced from prothrombin and production of activated 10.

if the clotting system didtn work, you’d lose a lot of blood.

hemophilia

  • A = factor 8

  • B = factor 9

  • C = factor 11

Life and times of RBCs and Platelets

1 microliter of blood

  • 5,000,000 RBCs

  • 200,000 platelets

  • RBCs last about 4 months, platelets last a few days.

  • RBCs and platelets are produced in bone marrow

    • start as precursor cell with nucleus which divides many times and some of them become RBCs through a process that includes losing the nucleus. blood cells go into blood vessels in bones and go into circulation.

    • RBC = erythrocyte. creating RBCs is erythropoesis.

    • platelets are fragments of cells. they come from megokaryocytes that is a big cell with a lot of cytoplasm. they break off and they go into circulation.


the spleen is in left upper abdomen. it recognizes old RBCs and take them out of circulation and break them down. monocytes break down old RBCs by engulfing them so that they can be reused. RBCs have iron, which is recycled. this process also happens a little bit in the liver.


RBCs bring oxygen to body. low O2 = not enough RBCs.

Erythropoietin (a hormone) tells body to make RBCs when there is low oxygen the kidney releases it.

thrombopoetien tells body to produce platelets,

Blood cell lineages

all blood cells come from bone marrow in certain places ex the head of femur and humorous, flat bones.

all blood cells have a common precursor: pluripotent hematopoietic stem cell.

  • myeloid lineage

    • RBCs, megakaryocyte (produce platelets), monocyte (become macrophages), neutrophil, eosinophils, basophils

    • mast cells

  • lymphoid lineage

    • B cells (make antibodies), T cells, natural killer cells

dendritic cells come from both lineages.