Lecture - Mixed Flashcards
The maintenance of circulatory hemostasis is achieved through the process of balancing
bleeding (hemorrhage)
clotting (thrombosis)
4 Major Components of Hemostasis
Vascular system
Thrombocytes (platelets)
Blood Coagulation Factors
Ultimate tissue repair
Processes involved in hemostasis following injury to a small blood vessel:
- Blood vessel spasm
- Formation of a platelet plug
- Contact among damaged blood vessel, blood platelet, and
coagulation proteins - Development of a blood clot around the injury
- Fibrinolytic removal of excess hemostatic material to
reestablish vascular integrity
Types of Blood Vessels
Arteries - arterioles
Veins - venules
Capillaries
Tissue Zones
- Tunica adventitia / Tunica
Externa - Tunica media
- Tunica intima / Tunica interna
a reflex in which blood vessels narrow to increase blood pressure.
Vasoconstriction
Vasoconstriction caused by
thromboxane A2
promotes vasoconstriction
Epinephrine
serotonin
ensures rapid lysis of fibrin clots
plasminogen
Regulates the permeability of the inner vessel wall and provides the principal stimulus to thrombosis following injury to a blood vessel.
Endothelium
Involved in the clotting process by producing or storing clotting components
Endothelium
Rich with plasminogen activator, which, if appropriately stimulated, is released and activates plasminogen
Endothelium
synthesized by the endothelium from prostaglandin precursors and strongly inhibits platelet aggregation and adhesion
prostacyclin
where they act as modulators of vasomotor tone, cell proliferation, and hormone production
Endothelins
Endothelin-1 is produced in
endothelial cells
vascular smooth muscle cells
endothelin acts as modulator in
vasomotor tone
cell proliferation
hormone production
Endothelin-2 produced in
predominantly within the kidney and intestine
smaller amounts produced in the myocardium, placenta, and uterus
Endothelin-3 found in
high concentrations in the brain - proliferation and development in neurons and astrocytes
found throughout the gastrointestinal tract and in the lung and kidney.
play an important role in the initiation, progression, and clinical complications of various forms of inflammatory and degenerative vascular diseases.
Endothelial Dysfunction
Stimuli of Endothelial Dysfunction
Immunoregulatory Substances (TNF & IL-1)
Viral Infection and Transformation
Bacterial Toxins
Cholesterol / Oxidatively modified lipoproteins
Disruption of the endothelium directly activates all four components of hemostasis.
• After this event, the following events take place:
- Initially, rapid vasoconstriction for up to 30 minutes reduces blood flow and promotes contact activation of platelets and coagulation factors.
- In the second phase, platelets adhere immediately to the exposed subendothelial connective tissue, particularly collagen. The aggregated platelets enhance sustained vasoconstriction by releasing thromboxane A2 and vasoactive amines, including serotonin and epinephrine.
- In the third phase, coagulation is initiated through both the intrinsic and extrinsic systems.
- Finally, fibrinolysis occurs following the release of tissue
plasminogen activators (t-PAs) from the vascular wall. Fibrinolytic removal of excess hemostatic material is necessary to reestablish vascular integrity.
Essential Factors for Vascular Integrity
- Circulating functional platelets
- Adrenocorticosteroids
- Ascorbic Acid
The integrity of arterioles and venules depends on
vasoconstriction
platelet plug
fibrin clot
ultimate importance in damaged arteries
Vasoconstriction
Veins contain what percent of blood volume
70%
Veins, which contain 70% of the blood volume, may rupture with
slight increase in hydrostatic pressure
proceeds initially through a phase characterized by mitotic division of a progenitor cell, followed by a wave of nuclear endoreduplication.
Megakaryocytopoiesis
proceeds initially through a phase
characterized by mitotic division of a progenitor cell,
followed by a wave of nuclear endoreduplication
Megakaryocytopoiesis
the process in which chromosomal material (DNA) and the other events of mitosis occur
Endoreduplication
stimulate the production and maturation of megakaryocytes
Thrombopoietin
Thrombopoietin activity results from several different cytokines
erythropoietin
IL-3
granulocyte-macrophage colony-stimulating factor (GM-CSF)
erythropoietin, IL-3, and granulocyte-macrophage colony-stimulating factor (GM-CSF) have been shown to be able to increase
megakaryocyte size
maturational stage
ploidy
10-24 mm, round nucleus, N/C ratio 3:1
MEGAKARYOBLAST
chromatin of megakaryoblast
homogenous
loosely organized
granules are absent by wright’s stain
megakaryoblast
Bone Marrow: 20% of megakaryocyte precursors in bone marrow
Peripheral Blood: 0%
megakaryoblast
15-40 mm, indented nucleus, condensed chromatin
promegakaryocyte
granules are present, n/c ration 1:2
PROMEGAKARYOCYTE
REFERENCE INTERVAL:
Bone Marrow: 25% of megakaryocyte precursors in bone marrow
Peripheral Blood: 0%
PROMEGAKARYOCYTE
largest bone marrow cells, ranging up to 160 mm in size
MEGAKARYOCYTE
MEGAKARYOCYTE n/c ratio
1:12
multilobular, not multinucleated
megakaryocyte
2 to 4 mm
no nucleus
platelets
Platelet’s color of cytoplasm and granules
cytoplasm - light blue
granules - fine red-purple
appearance of inactive or unstimulated platelet
thin
smooth surfaced disc
alteration in cellular shape of platelet is triggered by
cytoplasmic calcium
Stronger stimulation causes platelets to
become sticky without losing their discoid shape
GLYCOCALYX also known as
fluffy coat
these surrounds the cellular membrane of the platelet externally.
glycocalyx or fluffy coat
unique among the cellular components of the blood
glycocalyx or fluffy coat
glycocalyx or fluffy coat is composed of
plasma proteins and carbohydrate molecules
- located directly beneath the cell membrane of platelet
- provide structure of the platelet to maintain its discoid shape
- maintains the position of the organelles
MICROFILAMENTS & MICROTUBULES
• secondary system of microfilaments is functional in
internal organization
secretion of blood coagulation products, such as fibrinogen
most abundant granules
alpha
enumerate alpha granules
heparin-neutralizing platelet factor 4 beta-thromboglobulin platelet-derived growth factor platelet fibrinogen fibronectin vwf thrombospondin
dense granules also known as
delta granules
- store hydrolase enzymes
lysosomes
Dense or Delta Granules contains
Serotonin
ADP
ATP
Calcium
Other Cytoplasmic Constituents
- Contractile proteins, including actomyosin (thrombosthenin), myosin, and filamin
- Glycogen
- Enzymes of the glycolytic and hexose pathways
megakaryocyte produces
1,000-2,000 platelets
Marrow transit time / maturation period of megakaryocyte
5 days
Platelets initially enter the spleen & remains for
2 days
_____ of the total number of platelets are in systemic circulation
2/3
____ exists as pool of platelets in the spleen that free exchange with the general circulation
1/3
A normal person has an average of ____ platelets in the systemic
circulation.
Range:
250 × 109/L
150 ×109/L to 450 × 109/L
Platelet turnover or effective thrombopoiesis averages
35 ×109/L ± 4.3 × 109/L/day
The life span of a mature platelet is
9.0 days ± 1 day
At the end of their life span, platelets are phagocytized by the
liver and spleen
mononuclear phagocytic system
2 important players in primary hemostasis
blood vessels
platelets
Largest artery
aorta
- if blood comes out from vessel, instead of closed system what will happen
formation of petechiae
purpura
ecchymoses
- noncontact surface in vivo
Endothelium
contact surface, when exposed hemostatic mechanism will start
Sub endothelium
involved in secondary hemostasis
Blood coagulation factors
Mechanism of hemostasis only works on
medium sized vessels
- end point of primary hemostasis
Formation of platelet plug
doesn’t have tunic
Capillaries
epithelium of Surface endothelium
simple squamous
found in tunica media
collagen/smooth muscles
vasobasorum
blood vessels that gives nourishment and blood to blood vessels
vasobasorum found in
tunica externa
- product of activated platelet that will prolong platelet adhesion and vasoconstriction, byproduct of eicosanoids or the thromboxane pathway of cyclooxygenase pathway
Thromboxane A2
- only interleukins secreted by monocyte and macrophage
Tumor necrosis factor/IL1
these makes collagen
fibroblasts
endo multiplication of DNA, only lobes increase called polyploid cells
Endomitosis
the normal percentage of megakaryocytic cells are found in the bone marrow
1%
The earliest recognizable by microscopy
megakaryoblast
biggest in bone barrow or mother cell of platelets
Meta mega/mature karyocyte
no cytokinesis or late telophase, formation of?
Polyploids
simple endothelial cells that lines delicate organs like liver, spleen, BM
Sinusoids
Sinusoids lines delicate organs like
BM
liver
spleen
Platelet will stay at sinusoids for
9-11 days or 8-10 days
has big role on erythropoiesis and has a big role on thrombopoiesis
IL-3
pan myeloid factor, affects all cell line
• GM-CSF
more ploidy
greater number of lobes
how to get chromosome numbers
2n
Megakaryocytes are not usually found in blood, what happens if there are some?
megakaryocytic leukemia
Do we find platelets in bone marrow?
yes
Most important criterion in determining the age of the cell
chromosome- fine and linear
Platelets take what dyes
azure dyes
zone for adhesion of platelets
peripheral zone
zone where actomyosin or thrombosthenin, microfilaments, microtubules are found
Sol-gel zone
responsible for disk shape
microtubules
Not greatly stainable under electron micrographs they are gray colored
Alpha granules
Platelets can do aerobic glycolysis due to presence of
mitochondria
- an internal membrane structure found in platelets
Canalicular system
Adhesion is direct or indirect
indirect
vWF produced in
Weibel-palate bodies
Weibel-palate bodies found in
plasma
these also produce vWF aside from Weibel-palate
Megakaryocytes
3 primary steps in hemostasis
Adhesion
secretion (release mechanism)
aggregation
Upon exposure of sub endothelium, this will happen
adhesion
a loose mass (mesh) that will be strengthened by secondary hemostasis
Platelet plug formation
glycoproteins attached on surface of platelets
GP1B
GP5
GP9
this will engender (cause) platelet aggregation
ADP
receptors for fibrin
IIb
IIIa
Functional platelets adhere to
subendothelial collagen
these are assessed using platelet aggregometry
Platelet adhesion, aggregation, and secretion
PRP aggregometry is performed using
a light-transmittance aggregometer
whole-blood platelet aggregometry, platelet aggregation is measured by
electrical impedance.
used for the simultaneous measurement of platelet aggregation and the secretion of adenosine triphosphate (ATP) from activated platelet dense granules
Whole Blood/Optical LumiAggregometer
these are used to test for abnormalities of specific membrane binding sites.
platelet agonists
Aggregation is dependent in
calcium and energy (ATP)
Aspirin (blood thinner) will block
cyclooxygenase
thromboxane
eicosanoid
prostaglandin pathways
to stop production of thromboxane A2
potent platelet aggregator and stimulator
Thromboxane A2
blood clot, aggregates of platelets superimposed by fibrin
Thrombus
Secondary hemostasis endpoint
- stable fibrin clot in vivo (fibrin polymer)
Electronic particle counter principle
coulter principle
works in electrical impedance
Template bleeding time
obsolete, used to be the gold standard
When antibody coats a particle, it will activate
classical pathway of complements that will result in lysis of platelets
Not enough glycoproteins 1B, 5 and 9
Bernard-Soulier syndrome
Not enough glycoproteins 2b, 3a
Glanzmann diseases
Defect usually is in
release mechanism
- reactive condition
thrombocytosis
release of Pf3 or PPL(phospholipid)- which plays a big role in forming stable fibrin clot.
secondary hemostasis
substance responsible for extrusion of serum from the clot - clot retraction
platelet contractile protein, THROMBOSTHENIN/ACTOMYOSIN
plays a big role in forming stable fibrin clot in secondary hemostasis
Pf3 and phospholipid
Functions of platelets
Primary hemostasis
Secondary hemostasis
Clot retraction
Localization of bacteria and other small objects
Platelets are composed of
60% proteins
30% lipids
8% carbohydrate
Mainly glycogen, sulfate mucopolysaccharides, various minerals, water and nucleotides
Lipids- phosphatidylethanolamine and phosphatidylserine
4 parts of platelet
Peripheral zone
Sol-gel zone
Organelle zone
Membranous system
the fuzzy coating, primarily composed of glycoproteins (GP)
Glycocalyx
receptors for vWF
GPlb/V/IX
major component of plasma membrane
arachidonic acid
lies directly beneath the glycocalyx and is composed of asymmetrically distributed phospholipids embedded with integral proteins
plasma membrane
site where messages from the external membrane are translated into chemical signals causing activation and a physical change in the platelets.
sub membranous area
receptors identified in sub membranous area
ADP collagen serotonin epinephrine thrombin vWF Factor V Factor Xa
zone that lies beneath the plasma membrane.
Sol-gel zone
Sol-gel zone is composed of
Microfilaments and microtubules
responsible for clot retraction
actomyosin (thrombosthenin)
maintains the platelet’s disc shape
microtubules - tubulin
called the centromere
Organelle zone
Part where the secretory products come from.
Organelle zone
play an important role in platelet aggregation especially its product, ADP
Dense/delta granules
The platelets can also do anaerobic glycolysis due to
glycogen granules
2 types of membranous system
dense tubular system
surface connected system
derived from smooth endoplasmic reticulum and sequesters calcium for platelet activation processes.
dense tubular system-
an invagination of the plasma membrane, acts as a canal for the release of the granule contents and cytoplasm to the exterior of the platelet
surface connected system
This system is also involved in platelet phagocytosis.
surface connected system
This is found in hemorrhagic diathesis(( bleeding tendency)
Hemmeler’s anomaly
Hermansky-pudlak syndrome
defect when no azurophilic granules is found in cytoplasm of
platelets. The absolute platelet count is within reference range.
Hemmeler’s anomaly
Platelets have storage pool deficiency.
Hermansky-Pudlak syndrome
found in albinos , there is hemorrhagic diathesis, dense bodies storage pool disease
Hermansky-Pudlak syndrome-
appearance of atypical platelet
giant 4-7 um
increase size of hyalomere
granule is decreased or absent
bizarre or irregular shapes
- defects where there is decreased number of alpha granules
Gray platelet syndrome
when platelets are found encircling the borders of neutrophils, seen in patients whose blood was anticoagulated with EDTA
Platelet satellitosis/ platelet satellitism
This phenomenon is thought to be due to a serum factor that reacts in the presence of EDTA.
Platelet satellitosis/ platelet satellitism
occurs within the intravascular
compartment lined with endothelium
HEMOSTASIS
A tightly regulated balance between formation and dissolution of hemostatic plugs modulated by a series of enzymes and scaffolding proteins.
PHYSIOLOGIC HEMOSTATIC SYSTEM
Factors involved in Normal
Hemostasis and Thrombosis
Plateletes, Granulocytes & Monocytes
Coagulation Protein Sytem (Clot Forming)
Fibrinolysis Protein System (Clot Lysing)
Anticoagulation Protein System ( Regulating)
serves to form thrombin that initiates the proteolysis of fibrinogen, leading to fibrin clot formation
Coagulation System (Clot Forming)
→ functions to lyse the clot formed by thrombin
Fibrinolytic Sytem (Clot Lysing)
regulates all enzymes of the coagulation and fibrinolytic systems, so that no inappropriate excess of clotting or bleeding occurs.
Anticoagulation System (Regulating)
Vasoconstriction is a short-lived reflex reaction of the smooth muscle in the vessel wall produced by the
sympathetic branches of the autonomic nervous system
increases the adhesiveness of platelets
ADP
Platelet during adhesion will transform from ________ to ______ which produces surface membrane organization
disc shape to a sphere with pseudopods
Internal contraction of the platelet results in release of granular contents of
alpha granules
dense granules
lysosomal granules
Platelets adhere at sites of mechanical vascular injury and then undergo activation and express what functional glycoprotein —- also referred to as?
IIb/IIIa
Alpha 2b Beta 3
Which receptors will mediate the recruitment of local platelets by forming fibrinogen bridges between platelets—a process called platelet cohesion.
glycoprotein IIb/IIIa
A process forming fibrinogen bridges between platelets
platelet cohesion
Glycoprotein ____ is specific for
platelets.
IIb/IIIa
Glycoprotein ______ is the most abundant platelet membrane protein (with approximately _______ receptors per platelet).
IIb/IIIa
50,000
gold standard test to determine platelet function.
Platelet aggregation
Agents capable of producing platelet aggregation in vitro (an energy dependent process):
Collagen
Proteolytic enzymes (thrombin)
Biological amines (epinephrine and serotonin)
results from bridges formed by fibrinogen in the presence of calcium which produces sticky surface on platelets
Aggregation
If these aggregates are reinforced by fibrin, they are referred to as a
thrombus
Aggregation of platelets by at least one pathway can be blocked by substances such as:
PGE (prostaglandin E)
adenosine
- provides basis for platelet consolidation & stabilization.
Fibrinogen
This process involves the precipitation of polymerized fibrin around each platelet
PLATELET PLUG CONSOLIDATION & STABILIZATION
Result of platelet plug consolidation and stabilization
fibrin clot
Fibrin clot will produce
irreversible platelet plug
Quantitative Determination of Platelet
Electronic particle counter
examination of stained blood film
done if the platelet count is normal → assessment of platelet function
Qualitative Assessment of Platelet
Qualitative Assessment of Platelet
a. PBS
b. Platelet Count
c. Template Bleeding Time
d. Petechiometer
e. Platelet Aggregation
f. Platelet lumiaggregation (release)
g. Platelet Antibodies (IgM and IgG)
h. Platelet Membrane Glycoproteins
i. Platelet factor IV
k. Thromboxanes
In vivo measurement of platelet adhesion and aggregation on locally injured vascular subendothelium.
Bleeding Time with and without Aspirin
Provides an estimate of the integrity of the platelet plug and thereby measures the interaction between the capillaries and platelets
Bleeding Time with and without Aspirin
Reflects the number and quality of platelets, fibrinogen concentration, fibrinolytic activity, and packed red cell volume.
Clot Retraction
The degree of clot retraction is __________ to the number of
platelets & __________ to the hematocrit and the level of the blood coagulation factor fibrinogen.
directly proportional
inversely proportional
The principle of the test is that platelet-rich plasma is treated with a known aggregating agent. If aggregated, cloudiness or turbidity can be measured using a spectrophotometer.
Platelet Aggregation
Aggregating agents
ADP Collagen Epinephrine Ristocetin Snake venom Thrombin
Available techniques can include complement fixation methods, lysis of chromium 51 labeled platelets, assays of platelet-bound immunoglobulins, and competitive inhibition assays.
Antiplatelet Antibody Assays
VASCULAR DISORDERS
- Purpura associated with direct endothelial cell damage.
- Purpura associated with an inherited disease of the connective tissue.
- Purpura associated with decreased mechanical strength of the microcirculation.
- Purpura associated with mechanical disruption of small venules.
- Purpura associated with microthrombi (small clots).
- Purpura associated with vascular malignancy.
Demonstrates the smallest platelets seen
Wiskott-Aldrich
syndrome
Characterized by the presence of large platelets and the presence of Döhle-like bodies in the granulocytic leukocytes
May-Hegglin
anomaly
Disorder that exhibits giant platelets and thrombocytopenia
Alport syndrome
Demonstrates the largest platelets. In this disorder, it has been demonstrated that the giant platelets are probably an artifact of the slide
Bernard-Soulier syndrome (giant platelet syndrome)
3 types of thrombocytopenia
Disorder of production
disorder of destruction or utilization
disorder of platelet distribution
Hereditary or familial thrombocytosis associated with ger_x0002_mline mutations of the thrombopoietin (THPO) gene in the THPO receptor (MPL) gene
THROMBOCYTOSIS
associated with myeloproliferative neoplasms and/or myelodysplastic disorders (clonal thrombocytosis associated with somatic mutations of JAK2[V617F], MPL, and additional currently unknown genes)
THROMBOCYTOSIS
reactive disease
secondary thrombocytosis
TYPES OF PLATELET DYSFUNCTION
a) Acquired
b) Drug-Induced
c) Platelet Membrane Receptors
d) Hereditary
Types of acquired platelet dysfunction
Myeloproliferative Uremia Miscellaneous Paraprotein Cardiopulmonary bypass and platelet function
Types of hereditary platelet dysfunction
i. Bernard-Soulier Syndrome
ii. Glanzmann Thrombasthenia and Essential Athrombia
iii. Hereditary Storage Pool Defect