Lecture 21 - Hemostasis Flashcards
what are blood groups determined by?***
presence or absence of specific marker molecules on the cell membrane of RBCs
what are antigens?
substances that the body does not recognize as belonging to the “self
what do antigens trigger?
defensive response from the immune system
what are antigens made of
generally large proteins, but can include carbohydrates, lipids and nucleic acids
what are antibodies also called
immunoglobulins
what are antibodies produced by
plasma cells
what do antibodies do
attach to specific antigens
our bodies produce antibodies in response to what?
in response to foreign antigens
is the antibody-antigen response induced?
yes
name 2 groups of antigens on RBCs that may cause significant harm to patients
ABAO blood group and Rh blood group
ABO blood typing designates the presence/absence of which 2 antigens
A and B antigens
what type of proteins are A and B antigens
glycoproteins
how are ABO blood types determined
genetically
Blood type A has antibodies to….
antibodies to B antigen in blood plasma: anti-B antibodies
an individual with type B blood has which tupe of naturally formed antibodies
anti-A antibodies
an individual with blood type AB has which naturally formed antibodies
they have both A and B antigens so do not have naturally formed antibodies to either of these
people with blood type O have which kind of antibodies and antigens presence
lack A and B antigens on their erythrocytes, both have both anti-A and anti-B antibodies circulating in blood plasma
what initiates the formation of antibodies
body must first be exposed to the foreign antigen before an antibody can be produced
how is the human immune system exposed to A and B antigens at an early age
ABO blood group antigens are found in foods and microbes throughout nature, exposed at an early age –> antibodies are formed naturally
describe the series of events following a transfusion of incompatible blood
- RBCs with foreign antigens appear in the blood stream –> trigger an immune response
- antibodies attach to the antigens on the membranes of the transfused RBCs
-agglutination: Y shaped antibodies attach randomly to more than one foreign RBC –> form clumps
what are the consequences of agglutination in the body
- clumps block small blood vessels throughout the body –> deprive tissues of oxygen and nutrients
- hemolysis: as erythrocyte clumps degrade –> hemoglobin released into blood stream
-load of hemoglobin released can be toxic to the kidney –> quickly develop kidney failure
anti-B antibodies will cause agglutination and hemolysis if…
they ecounter erythrocytes with B antigens
anti-A antibodies will cause agglutination and hemolysis if…
they encounter erythrocytes with A antigens
if a blood sample agglutinates with both anti A and anti B antibodies, what is the ABO type?
AB
if a blood sample agglutinates with anti-B antibodies but not anti-A antibodies, what is the ABO blood type?
B
if a blood sample only agglutinates with anti-A antibodies, what is the bloodtype?
A
If the blood sample does not agglutinate with anti B nor anti A antibodies, what is the blood type
O
Type A…
antigens on blood cells:
antibodies in plasma:
Donates to:
receives from:
antigens on blood cells: A
antibodies in plasma: B
Donates to: A, AB
receives from: A, O
Type B…
antigens on blood cells:
antibodies in plasma:
Donates to:
receives from:
Type B…
antigens on blood cells: B
antibodies in plasma: A
Donates to: B, AB
receives from: O, B
Type AB…
antigens on blood cells:
antibodies in plasma:
Donates to:
receives from:
Type AB…
antigens on blood cells: A, B
antibodies in plasma: none
Donates to: AB
receives from: universal acceptor
Type O…
antigens on blood cells:
antibodies in plasma:
Donates to:
receives from:
antigens on blood cells: none
antibodies in plasma: A, B
Donates to: universal donor
receives from: O
Rh blood group is classified according to what
presence, or absence of a erythrocyte antigen Rh
in what animal was the Rh antigen first discovered
rhesus macaque
which Rh antigen is clinically important
although dozens have been identified, only D is clinically important
What determines wether someone is Rh+ vs. Rh -ve
Rh+ = D antigen present on erythrocytes
Rh- = lack D antigen on erythrocytes
when are Rh antibodies produced? contranst this to ABO antibodies
antibodies to Rh antigen are produced in Rh- individuals only after exposure to the antigen vs. ABO group antibodies which are preformed
what are 2 ways in which Rh antibodies may be formed in an Rh negative individual
following a transfusion with incompatible blood, or birth of an Rh+ baby to an Rh- individual
what happens when an Rh- individual gives birth to an Rh+ baby, given that this is their second Rh+ve baby
immediately after the first birth, the Rh- parent would be exposed to baby’s Rh+ cells –> immune system of parent begins to generate anti-Rh antibodies after exposure –> during second pregnancy, Rh antibodies produced can cross the placenta into fetal blood stream and destroy fetal RBCs
describe the action and mechanism of RhoGAM
action: temporarily prevent the development of Rh antibodies in the Rh- parent
MechanismL antibodies destroy any fetal Rh+ erythrocytes that may cross the placental barrier
how many blood groups are there in dogs
more than 12, their RBCs may contain any combination of these b/c each blood group is inherited independently
what is the most important dog blood group
Dog erythrocyte antigen (DEA) 1.1
do dogs normally have antibodies against other canine blood group antigens
normally, dogs do not have any antibodies against any of the antigens present in their own blood or other canine blood group antigens unless previously exposed to them via. transfusion
how many known blood types are there in cats? name them!
4: A, B, AB, mic
what is the most common blood group in cats? what about the others?
A = most common
B = higher in certain breeds
AB = rare
do cats have antibodies against blood group antigens they lack
yes
what is the universal donor amongst cats
there is no universal donor
How many blood groups are there in horses? name them!
7: A,C,D,K,P,Q,U.
each blood group in horses can have multiple cell membrane proteins. what are they referred to as?
A to G
how many allelic combinations of blood types can horses have
400,000
do horses possess antibodies against RBC antigens that they do not possess
no, unless they are exposed to a different blood type (ex. transfusion)
which animals is crossmatching for blood types not necessary for the first transfusion?
dogs, horses
Define hemostasis
process by which the body seals a ruptured blood vessel and prevents further loss of blood
what is hemostasis effective in dealing with
small, simple wounds
name the 3 steps of hemostasis in sequence… what happens when there is a failure in any one of these steps
1.vascular spasm,
2.formation of a platelet plug,
3. coagulation (blood clotting )
failure = hemorrhage
describe vascular spasm
platelets secrete vasoconstrictors that cause vascular spasms in broken vessels
describe the formation of temporary platelet plugs to stop bleeding
- collagen fibers are exposed
- platelets become sticky and release chemicals to attract more platelets
- ‘plug’ is formed that slows loss of blood within 3-5 minutes
describe coagulation
- clotting factors in blood reinforce platelet ‘plug’
- calcium needed
chemical reactions –> form thrombin (enzyme) - thrombin joins fibrinogen into netlike fibrin
- blood cells are trapped in fibrin meshwork to form a hard clot
different precursors of fibrin polymer
fibrinogen –> fibrin –> fibrin polymer
what are 4 critical components to coagulation***
prothrombin –> thrombin –> fibrinogen –> fibrin
how many stages are there in coagulation
3
when are clotting factors activated
- blood vessels are broken
are clotting factors active or inactive in blood
inactive
clotting factors are primarily secreted by ____ and _____
liver and platelets
what does the the liver require to produce clotting factors
fat soluble vitamin K
what is a common cofactor required by clotting factors
calcium ion as a cofactor
What happens in stage 1 of the coagulation pathway
production of active thrombokinase by the extrinsic and intrinsic pathway
describe where chemicals are released from in the extrinsic pathway
chemicals are released from damaged tissues
describe where chemicals are released from in the intrinsic pathway
chemicals present in blood
do both pathways need to be activated for effective homeostasis?
yes
what happens in stage 2 of the blood coagulation pathway
conversion of prothrombin to thrombin by the thrombokinase produced in stage 1
what happens in stage III of the blood coagulation pathway
conversion of fibrinogen to fibrin and production of fibrin clot by thrombin produced in stage II
Fibrinogen:
Type of molecule: ?
Source: ?
Pathways: ?
Fibrinogen:
Type of molecule: plasma protein
Source: Liver
Pathways: common, converted into fibrin
Prothrombin:
Type of molecule: ?
Source: ?
Pathways: ?
Prothrombin:
Type of molecule: plasma protein
Source: liver*
Pathways: common; converted into thrombin
What are 2 conditions that hasten clotting?
- rough spot in the blood vessel lining
- abnormally slow blood flow
what are 2 conditions that oppose clotting
- smooth surface of lining of blood vessels does not allow platelets to stick
- antithrombins: substances in blood that oppose or inactivate thrombin (ex. heparin)
Thrombosis
abnormal clotting of blood in an unbroken vessel
thrombus:
a clot that attaches to the wall of the blood vessel
embolus
a clot that comes off the wall of the blood vessel and travel in blood stream (travels to small vessel and blocks flow)
embolism
blockage of blood flow by an embolus that lodges in a blood vessel
infarction
cell death that results from embolism
- is responsible for most strokes and heart attacks
what are 3 bleeding disorders
- thrombocytopenia
- deficiency of clotting factors due to impaired liver function
- hemophilias
what is thrombocytopenia
the number of circulating platelets is deficient (<50,000/ul)
what does thrombocytopenia cause
spontaneous bleeding from small vessels all over the body
what are hemophilias
hereditary bleeding disorders due to deficiency of clotting factors
what does aspirin do
thins blood, can prevent heart attack and stroke
what is the aPTT test used to evaluate
intrinsic pathway: evaluates the coagulation factors XII, XI, IX, VIII, X, V, II (prothrombin and fibrinogen)
what is the PT test used to evaluate
extrinsic pathway: evaluates coagulation factors VII, X, V, II and I (fibrinogen)
how is a PT test conducted
- a sample of patients blood is obtained and centrifuged.
- PT test is performed by adding patients plasma to some source of tissue factor
- kept in a water bath at 37*
- test is timed until the plasma clots (prothrombin time)
what does a prolonged prothrombin time indicate?
indicates a deficiency in any factors VII, X, V, prothrombin or fibrinogen
how is an aPTT test conducted
- activating substances added to plasma to start the intrinsic pathway of the coagulation cascade
- measure partial thromboplastin
what is partial thromboplastin
the time it takes for a clot to form, measured in seconds
how long should prothrombin time be
~12 seconds
how long should partial thromboplastin time take
25-39 seconds
what does aPTT measure***
measures the integrity of the intrinsic system and common clotting pathways
GIRL you better know everything about PT and PTT tests!!
increased levels of PT or aPTT means…?
a clotting factor may be missing or defective
which pathway is affected if PT is prolonged but aPTT is normal
extrinsic
which pathway is affected if PT is normal but aPTT is prolonged
intrinsic (and common????????????????? lmk if you know the definite answer)
which pathway is affected if both PT and aPTT are affected
common or …?????? ( again lmk if another one is affected)
