Leukocytes, Platelets, and Hemostasis Study Guide Flashcards
amount of leukocytes in a microliter (ul) of blood
4,800 to 10,800 (less than erythrocytes)
diapedesis
how leukocytes cross blood vessel walls to travel to areas of need
Positive Chemotaxis
phenomenon in which damaged/infected cells provide a chemical trail for leukocytes to follow
Leukocytosis
elevated number of leukocytes (> 11,000/µl)
Leukopenia
decreased number of leukocytes
5 types of leukocytes in order of abundance
Neutrophils (Most Abundant)
Lymphocytes.
Monocytes.
Eosinophils.
Basophils (Least Abundant)
Agranulocytes
Lymphocytes
Monocytes
Granulocytes
Neutrophils
Eosinophils
Basophils
Lymphocytes
- Account for 25% of all leukocytes
- Often classified by diameter – small, medium, and large
- Largely live in lymphoid tissues – lymph nodes and spleen – versus the bloodstream
- T Lymphocytes (T-Cells): directly fight against virus-infected and tumor cells
- B Lymphocytes (B-Cells): give rise to antibody-producing plasma cells
Monocytes
- Account of 3-8% of all leukocytes
- Are the largest of all leukocytes
- Differentiate into highly mobile macrophages with enormous appetites
- Able to activate lymphocytes to mount an immune response
Neutrophils
- The most numerous type of leukocyte (50-70% of all leukocytes)
- Function as “bacteria-slayers” - very active phagocytes
- Are chemically attracted to inflammation
Eosinophils
- Account for 2-4% of all leukocytes
- Lead the counter-attack against parasitic worms and other things too large to be phagocytized
- Play a role in responding to allergens and modulating the overall immune system response
Basophils
- Rarest leukocytes (0.5-1%)
- Granules contain Histamine – an inflammatory chemical that vasodilates vessels and attracts other leukocytes - and Heparin - an anticoagulant that assists the mobility of other leukocytes
What stimulates the creation of leukocytes?
Chemical messengers called interleukins or colony-stimulating factors (CSFs)
blood cells that differentiate from the myeloid line
monocytes (following monoblast and promonocyte)
blood cells that differentiate from the lymphoid line
Lymphocytes
- T Lymphocyte Precursors give rise to immature T-Cells which mature in the thymus
- B Lymphocyte Precursors give rise to immature B-Cells which mature in the bone marrow
leukemia
verproduction of abnormal leukocyteso
leukemia cause
- Typically, excessive leukocytes are descendants of a single cell undergoing un-regulated proliferation
- Excessive leukocytes impair normal function of red bone marrow
leukemia symptoms
severe anemia, bleeding, fever, weight loss, and bone pain
general premise of chemotherapy
Kills both normal and abnormal leukocytes → can help cancer, but also cause undesirable side effects
3 steps of hemostasis
Vascular Spasm
Platelet Plug Formation
Coagulation
platelet typical lifespan
They age quickly and degenerate within 10 days
Where do platelets come from
Fragments of very large cells called megakaryoctyes:
- A hormone called thrombopoietin regulates the formation of platelets
- A megakaryocyte undergoes repeated mitosis without cytokinesis yielding a very large cell
- Cytoplasmic extensions of the megakaryocyte rupture and release platelets into the bloodstream
platelet function
stopping blood loss / promoting blood clots
What happens after blood successfully clots (hemostasis)?
the blood clot will retract and dissolve. The clot is replaced with fibrous tissue, which more permanently prevents blood loss
two things that have anti-coagulant properties
Prostacyclin and nitric oxide have anticoagulant properties (prostaglandins that keeps platelets from sticking to each other or to the endothelial layer of vessel walls)
natural anticoagulant found in endothelial cells
Heparin
two aggregating agents
Adenosine Diphosphate (ADP): a potent aggregating agent and Serotonin and thromboxane A: messengers that enhance both vascular spasm and platelet aggregation
What works to stabilize a forming platelet plug (bound platelets)?
Von willebrand factor
What works to reinforce a formed platelet plug?
fibrin threads
mineral is essential to the formation of a blood clot
calcium
Phase I of III of coagulation
- Intrinsic vs Extrinsic Pathway; either triggered by tissue damaging events
- Both involve a series of clotting factors and end with the activation of Factor X
- Factor X complexes with Ca2+, Platelet Factor 3, and Factor V to make Prothrombin Activator
Phase II of III of coagulation
Prothrombin activator catalyzes the transformation of prothrombin to the active enzyme thrombin
Phase III of III of coagulation
- Thrombin converts soluble fibrinogen to fibrin
- Fibrin strands form the structural basis of a blood clot and cause plasma to become a gel-like trap catching formed elements
two growth factors are involved in blood vessel repair
- Platelet-derived growth factor (PDGF) stimulates smooth muscle cells and fibroblasts to form a connective tissue patch
- Vascular endothelial growth factor stimulates endothelial cells to multiply and restore the endothelial lining
enzyme that works to dissolve clots
Plasmin: the natural “clot-buster” – a fibrin digesting enzyme. The presence of a clot, triggers endothelial cells to secrete tissue plasminogen activator (tPA).
How is this plasmin/tpa used medically?
tPA can be given through IV to stroke patients to restore blood flow by activating plasmin
Thrombus
- a clot that forms in an unbroken vessel
- A thrombus can cause death of the tissue beyond the blockage
- Example: Myocardial Infarction
Embolus
- a clot that breaks away from the vessel wall and floats in the bloodstream
- An embolus wedged in a small vessel = an obstructing embolism
- Example: Pulmonary Emboli or Cerebrovascular Accident
two things that increase risk of blood clots
vessel arthrosclerosis or inflammation, slow blood flow (reduced mobility)
Thrombocytopenia
low volume of circulating platelets
- Severe cases cause to spontaneous bleeds with routine movement
- Symptom: petechiae
- Cause: suppression or destruction of red bone marrow
- Treatment: platelet transfusion
Hemophilia
a group of hereditary bleeding disorders; deficiencies of various clotting factors
- 2:3 types of hemophilia are X-linked - occur predominantly in males
- Symptoms: prolonged bleeding with minor tissue injury, repeated bleeds into joint spaces
- Treatment: fresh plasma transfusions; injections of clotting factors
