Blood, Hemostasis and Lymphatics Flashcards
antigen
any substance that causes an antibody response to be generated
antibodies
substances created by our immune cells and are capable of binding to foreign substances
blood typing
involves mixing blood w/ different antisera
ABO blood groups
based on having an A, B, both or no antigens on red blood cells
Rh blood group
a group of antigens discovered on the red blood cells of rhesus monkeys that is also present to some extent in humans, presence indicated by “+”
how do Rh antibodies develop?
they will only develop on Rh- blood only with exposure to the antigen
hemolytic disease of the newborn
this disease occurs in the fetus if the fetus is Rh+ while the mother is Rh- (and later develops antibodies); this causes issues for 2nd pregnancy if fetus is Rh+ (particular antibodies; IgG can be transported across placenta to confer protection to fetus) — antibodies in mother would bind to blood forming within fetus and destroys the blood
hemostasis
sequence of responses that stops bleeding and prevents hemorrhage from smaller blood vessels
platelet features
disc shaped, 2-4 micron cell fragments, no nucleus and a short lifespan
platelet production
pluripotent to myeloid stem cell, becomes megakaryoblast to megakaryocyte to platelets
what are the functions of a platelet?
stop blood loss from damaged vessels by forming a platelet plug and releasing chemicals that promote clotting/vascular spasm
what are the 3 mechanisms to reduce blood loss?
vascular spasm, platelet plug formation and blood clotting
vascular spasm
prompt constriction of a broken vessel; most immediate protection against blood loss
steps of platelet plug formation
adhesion, release reaction and aggregation
platelet adhesion
platelets stick to exposed collagen underlying damaged endothelial cells in vessel wall
platelet release reaction
release of serotonin (vasoconstriction), ADP (activates platelets) and thromboxane A2 (both)
platelet aggregation
clumping of platelets during wound healing (platelet plug)
blood clotting (coagulation)
Forms as platelets become enmeshed in fibrin threads
a blood clot contains…
platelets, fibrin and RBCs
formation of fibrin
cascade of reactions in which each clotting factor activates the next in a fixed sequence
thrombus
clot in an unbroken vessel
thromboembolus
clot travelling around in the blood stream
positive feedback in blood clotting
exposed collagen attracts platelets which bind to the damaged site; platelets become activated and attract more platelets which release substances that promote clotting and form a plug; clot growth stops once the binding sites are covered
extrinsic pathway
evokes clotting within a blood vessel if there is damage to the tissue outside the vessel
intrinsic pathway
cascade of clotting factors leading to the formation of a clot within an injured vessel
convergence of extrinsic and intrinsic pathways
(extrinsic) Ca2+ release activates factors X and V to form prothrombinase, (intrinsic) activated platelets to platelet phospholipids contribute to eventual activation of factors X and V + Ca2+ to form prothrombinase
common pathway
prothrombinase converts prothrombin to thrombin with the help of Ca2+; then thrombin produces insoluble fibrin threads that become strengthened fibrin threads with factor XIII
clot retraction & blood vessel repair
clot plugs ruptured area of blood vessel; platelet pull on fibrin threads causing clot retraction and edges of damaged vessel are pulled together - fibroblasts and endothelial cells repair the blood vessel
clot lysis (fibrinolysis)
dissolution of the clot; as son as clotting begins, the anti-clotting factor is also activated but much slower to act
fibrinolysis pathway
activated factor XII and tPA works on inactive plasminogen to turn it into active plasmin that breaks down fibrin and dissolves the clot
antiplatelet agents
e. g. aspirin - prevent platelet reaction from occuring
e. g. clopridogrel - prevent platelet “party”
anticoagulants
suppress/prevent blood clotting; e.g. heparin prevents formation of fibrin thread, warfarin is a vitamin K antagonist (clotting factors can’t work)
thrombolytics
break existing clots; e.g. tPa and streptokinase
what does the lymphatic system consist of?
lymph, lymphatic vessels, structures containing lymphatic tissue, red bone marrow
what are the functions of the lymphatic system?
drain excess interstitial fluid from tissue spaces and return it to blood, transport dietary lipids & lipid-soluble vitamins from the GI tract, carry out immune responses
where do lymphatic vessels originate?
start in the tissue sb/w capillary beds - “close-ended” lymph capillaries that lie adjacent to blood capillaries in the tissue spaces
how can lymph flow be aided?
similar to aiding venous return, by valves, skeletal muscle pump and respiratory pump
lymph drainage
returns excess fluid and plasma proteins to the circulation mainly by draining into the L or R subclavian through the right lymphatic or left thoracic duct
cisterna chyli
an enlarged pouch on the thoracic duct that serves as a storage area for lymph moving toward its point of entry into the venous system
primary lymphoid organs
the bone marrow and thymus; responsible immune cell production and education
secondary lymphoid organs
lymph nodes/nodules and spleen; where most immune responses occur
where are major lymph nodes located?
cervical, axillary and inguinal regions
why do lymph nodes have many afferent but few efferent vessels?
it slows the flow of lymph as it goes through the lymph node and allows immune cells (T and B cells) the opportunity to see what is being drained from the tissue
