Chapter 17 - Part 2 Flashcards
Name the 3 steps for stoppage of bleeding
- vascular spasm
- platelet plug formation
- coagulation (blood clotting)
What is a vascular spasm?
vasoconstriction of damaged blood vessel
What are the 3 triggers of vascular spasm?
- direct injury
- chemicals released by endothelial cells and platelets
- pain reflexes
Describe the platelet plug formation at site of blood vessel injury…
- platelets contact exposed collagen fibers
- become sticky
- degranulate - release chemical messengers
- causes more platelets to stick and release their contents
- plug forms within one minute
What is a set of reactions in which blood is transformed from a liquid to a gel called?
coagulation
What does coagulation reinforce the platelet plug with?
fibrin threads
Coagulation is a multistep process…how many substances and enzymes does it require?
30
What are procoagulants?
inactive plasma clotting proteins
What do antiproagulants do?
prevent clotting
What are the 3 phases of coagulation?
- prothrombin activator is formed (intrinsic & extrinsic pathways)
- prothrombin is converted into trhombin
- thrombin catalyzes the joining of fibrinogen to form a fibrin mesh
Name the two pathways to prothrombin activator.
- intrinsic pathway
2. extrinsic pathway
What does the instrinsic pathway use? and what is it triggered by?
uses factors present within the blood
triggered by negatively charged surfaces
What does the extrinsic pathway bypass? and what is it triggered by?
bypasses several steps of intrinsic pathway, so is faster
triggered by exposure to tissue factor or factor III
What does factor X complexes involve in order to form prothrombin activator?
Ca2
PF3
factor V
What is the result of phase 1 in hemostasis?
prothrombin activator is formed
What is the result of phase 2 in hemostasis?
prothrombin activator catalyzes the transformation from prothrombin to thrombin
What is the result of phase 3 in hemostasis?
blood clot forms
Describe the pathway of phase 3 that results in blood clot.
thrombin ->
fibrinogen -> fibrin ->
forms a mesh; traps blood cells ->
blood clot
What speeds up the healing process?
clot retraction and repair of tissue
Describe the 5 steps of clot retraction and repair of tissue.
- actin and myosin in platelets contract within 30-60 minutes
- platelets pull on the fibrin strands, squeezing serum from the clot
- edges of wound pull together
- PGDF stimulates rebuilding of vessel wall
- VEGF stimulates regrowth of endothelium lining the vessel
What is the breakdown of the scab called?
fibrinolysis
How long does it take to happen after clotting?
within 2 days
What is plasminogen in the clot coverted to?
- plasmin by tissue plasminogen activator (tpa), factor XII and thrombin
What is plasmin?
fibrin-digesting enzyme
What does plasmin do?
breaks fibrin down to fragments and eventually to amino acids
What are the two mechanisms preventing clots from becoming too large?
- swift removal and dilution of clotting factors
2. inhibition of activated clotting factors
What are the two factors preventing undesirable clotting?
- smooth endothelial lining of blood vessels
2. antithrombic substances nitric oxide and prostacyclin secreted by endothelial cells.
What type of disorder has undesireable clot formation?
thromboembolytic disorder
Name two thromboembolytic disorders and describe.
- thrombus - clot that develops and persists in an unbroken blood vessel
- embolus - a thrombus freely floating in the blood stream
What prevents thromboembolytic disorders and how?
- aspirin - prevents platelets from sticking together
- heparin - inhibits thrombin formation
- warfarin - inhibits clotting
What is a disorder that leads to widespread clotting through intact vessels?
disseminated intravascular coagulation
Describe disseminated intravascular coagulation.
severe bleeding occurs because residual blood is unable to clot
When can disseminated intravascular coagulation occur?
during pregnancy or a result of an incompatible blood transfusion
What bleeding disorder creates a deficient number of circulating platelets?
thrombocytopenia
What causes thrombocytopenia?
a suppression or destruction of bone marrow
What disorder happens as a result of the inability to synthesize procoagulants?
impaired liver function
What causes impaired liver function?
vitamin K deficiency, hepatitis, and cirrhosis
What types of disorders include several similar hereditary bleeding disorders?
hemophilias
What is the most common type of hemophilia? and why? is it most common in males or females?
hemophilia A
due to a deficiency of factor VIII
most common in males
What are the symptoms of hemophilia?
prolonged bleeding, especially into joint cavities
When are whole blood transfusions used?
when blood loss is substantial or when treating thrombocytopenia
In a transfusion packed red cells (plasma removed) are used to restore what?
oxygen-carrying capacity
Humans have different blood types based on what?
specific antigens on RBC membranes
What could happen if a blood transfusion was incompatible?
death
What is agglutination?
sticking together of red blood cells
What are the promoters of agglutination called?
agglutinogens
How many glycoprotein antigens do RBC membranes bear?
30
What is a humans blood type based on?
specific antigens on RBC membranes
Presence or absence of each antigen is used to classify blood cells into different groups. What are the two groups of blood?
ABO
Rh
Name the the 4 ABO blood groups?
A
B
AB
O
What are the ABO blood groups based on?
the presence or absence of agglutinogens (A or B) on the surface of red blood cells
What are anti-A or anti-B antibodies also called?
aggluntinins
When do anti-A or anti-B form in the blood?
at 2 months of age
How many Rh agglutinogens are there?
45
Which aggluntinogen causes strong reactions?
agglutinogen D
What does Rh+ indicate vs. Rh-?
Rh+ indicates presence of agglutinogen D
Rh- indicates absence of agglutinogen D
Anti-Rh antibodies are not automatically formed in Rh- individuals. When are they formed?
When a Rh- recipient receives Rh+ blood
What will happen if an Rh- individual receives Rh+ blood for a second time?
a typical transfusion reaction
What is the hemolytic disease of a newborn called?
erythorblastosis fetalis
Describe the 3 things that happen in a transfusion reaction
- donor’s cells are attacked by recipients plasma agglutinins
- they aggluinate and clog small vessels
- they rupture and release free hemoglobin into the bloodstream
What two things can a transfusion reaction result in.
- diminished oxygen-carrying capacity
2. hemoglobin in kidney tubules and renal failure
What is an agglutinogen?
antigen on RBC (glycoproteins)
What is an agglutinin?
antibodies in plasma (globulins)
