Hemostasis Hemorrhagic Disorders and Thrombosis

Slide 1 · Hemostasis, Hemorrhagic

Disorders, and Thrombosis

Physiologic mechanisms • bleeding phenotypes • thrombus formation

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Sequence normal hemostasis from vascular injury to fibrin stabilization and clot removal.

Connect platelet receptors, tissue factor, thrombin, and endothelial regulators to their functions.

Distinguish typical patterns of bleeding caused by platelet, coagulation, or vascular defects.

Explain thrombosis through Virchow triad, hypercoagulability, morphology, and clinical outcomes.

Slide 3 · One system, two pathological extremes

Insufficient hemostasis

Deficient platelets, coagulation factors, or vessel integrity

Spontaneous or provoked bleeding

Risk: Blood loss or vital-organ hemorrhage

Excessive or misplaced coagulation

Clots form within intact vessels or heart chambers

Thrombi obstruct flow or embolize

Risk: Tissue ischemia and infarction

Slide 4 · Why bleeding and clotting can coexist

Systemic activation of coagulation

Microvascular fibrin thrombi

Consumption of platelets and factors

Secondary hemorrhage

Disseminated intravascular coagulation is a key example of this paradox.

Slide 5 · The four phases of normal hemostasis

Transient vasoconstriction

Primary platelet plug

Fibrin reinforcement

Stabilization and resorption

Hemostasis is spatially restricted: Clotting is encouraged at an injury, not throughout the circulation.

Slide 6 · Vasoconstriction immediately reduces blood loss

Arteriolar contraction is the earliest reaction to vascular injury.

Neurohumoral reflexes and local endothelin contribute to the response.

The effect is transient and cannot alone provide durable hemostasis.

Platelet activation and coagulation must follow to prevent renewed bleeding.

Slide 7 · Primary hemostasis creates a platelet plug

Endothelial disruption

Subendothelial vWF / collagen exposed

Platelet adhesion + activation

Platelet aggregation

The initial platelet plug develops within minutes and needs later fibrin reinforcement.

Slide 8 · Secondary hemostasis reinforces the plug

Tissue factor exposed

Factor VII–dependent initiation

Thrombin generated

Fibrinogen → fibrin

Fibrin forms a meshwork that consolidates the primary platelet aggregate.

Slide 9 · Clot stabilization does not end regulation

Platelets contract through their cytoskeleton and compact the plug.

Factor XIII–dependent cross-linking strengthens the fibrin network.

Endothelial counterregulatory processes confine coagulation to injured tissue.

Subsequent fibrinolysis and tissue repair enable clot resorption.

Slide 10 · Three cellular and molecular partners

Platelets + coagulation proteins

Platelets adhere and build the primary plug

Membrane phospholipids support factor complexes

Thrombin produces fibrin and activates platelets

Vascular endothelium

Normal surface inhibits platelet activation and clotting

Injured or activated cells become prothrombotic

T-PA contributes to localized clot dissolution

Slide 11 · Platelets are specialized anucleate fragments

Bone marrow megakaryocytes release platelets into the bloodstream.

They normally circulate as small discoid, anucleate fragments.

Receptors, cytoskeletal machinery, and cytoplasmic granules support rapid responses.

Activated platelets provide a phospholipid surface for enzyme complexes.

Slide 12 · Adhesion and aggregation use different receptors

Receptor

Major ligand

Function

GpIb

Von Willebrand factor

Adhesion

GpVI; GpIa/IIa

Collagen

Adhesion

GpIIb/IIIa

Fibrinogen

Aggregation

Slide 13 · VWF bridges exposed collagen to GpIb

Exposed collagen

Matrix-bound vWF

Platelet GpIb binding

Firm platelet tethering

This adhesive bridge is particularly important where shear forces are high.

Slide 14 · Collagen is also a direct platelet ligand

GpVI and GpIa/IIa mediate platelet binding to exposed collagen.

The receptor pathways complement vWF–GpIb-mediated tethering.

Both platelet receptors and matrix ligands are required for normal adhesion.

Inherited deficiencies illustrate how failures in adhesion cause bleeding.

Slide 15 · Platelet activation changes shape and surface

Adhesion to exposed matrix

Discoid → spiky platelet

GpIIb/IIIa affinity rises

Phosphatidylserine exposed

The new membrane surface supports assembly of calcium-dependent coagulation complexes.

Slide 16 · Alpha granules provide adhesive and repair proteins

α-granules contain fibrinogen, vWF, and coagulation-related proteins.

Platelet factor 4 binds heparin and is relevant to immune-mediated HIT.

Fibronectin and platelet-derived growth factor contribute to repair responses.

P-selectin is present in granule membranes and appears at the surface after activation.

Slide 17 · Dense granules amplify platelet recruitment

Dense granules contain ADP, ATP, calcium, serotonin, and epinephrine.

Released ADP stimulates neighboring platelets through purinergic receptors.

Calcium supports membrane-associated coagulation reactions.

This release reaction helps turn local adhesion into a growing platelet plug.

Slide 18 · ADP and thromboxane recruit more platelets

Activated platelet

ADP release + TxA₂ synthesis

Additional platelet activation

Reinforced platelet aggregate

ADP acts through P2Y receptors; Thromboxane A₂ is generated through cyclooxygenase-dependent signaling.

Slide 19 · Thrombin links coagulation to platelet signaling

Thrombin activates platelets by proteolytically switching on PAR-1.

Platelet degranulation and aggregation therefore reinforce thrombin generation.

Activated platelet membranes promote additional coagulation reactions.

The platelet–thrombin feedback loop rapidly consolidates the plug.

Slide 20 · GpIIb/IIIa enables platelet aggregation

Platelet activation

GpIIb/IIIa conformation changes

Fibrinogen bridges platelets

Platelet–platelet aggregation

Fibrinogen forms bridges between receptors on adjacent activated platelets.

Slide 21 · Inherited defects map to distinct functions

Molecular defect

Impaired step

Named disorder

VWF

Adhesion

Von Willebrand disease

GpIb

Adhesion

Bernard–Soulier syndrome

GpIIb/IIIa

Aggregation

Glanzmann thrombasthenia

Slide 22 · Drug effects reveal platelet pathways

Cyclooxygenase inhibition

Aspirin reduces thromboxane A₂ synthesis

Platelet aggregation is impaired

The mechanism produces a mild bleeding tendency

P2Y₁₂ or PAR-1 antagonism

P2Y₁₂ blockade limits ADP-dependent signaling

PAR-1 antagonism interferes with thrombin signaling

Both target recruitment or activation pathways

Slide 23 · Platelet surfaces localize coagulation

Activated platelets expose negatively charged phospholipids.

Calcium bridges coagulation proteins to these surfaces.

Local assembly concentrates factors and accelerates enzymatic reactions.

Restriction of this surface to activated cells helps confine clot formation.

Slide 24 · Coagulation is an amplifying protease network

Inactive coagulation zymogen

Proteolytic activation

Active enzyme + cofactor

Activation of next factor

The result is highly amplified thrombin generation and insoluble fibrin deposition.

Slide 25 · The laboratory pathways are not the in vivo map

Laboratory assay model

Contact activation defines the intrinsic arm

Added tissue factor activates the extrinsic arm

Both feed a common pathway in test conditions

Coagulation in vivo

Exposed tissue factor is the major initiating trigger

TF–VIIa activates factors X and IX

IXa–VIIIa efficiently activates factor X

Slide 26 · Tissue factor initiates physiologic clotting

Vessel wall injury

Tissue factor becomes accessible

Tissue factor–VIIa complex

Activation of factor X and IX

Tissue factor normally resides in cells shielded from circulating blood.

Slide 27 · The intrinsic tenase complex activates factor X

Factor IXa

Factor VIIIa (cofactor)

Ca²⁺ + platelet phospholipid

Factor X → Xa

The factor IXa–VIIIa complex is a major physiologic route to generating factor Xa.

Slide 28 · Prothrombinase generates thrombin

Factor Xa

Factor Va (cofactor)

Ca²⁺ + phospholipid surface

Prothrombin (II) → thrombin (IIa)

Coagulation factor complexes use an enzyme, a substrate, a cofactor, and a catalytic surface.

Slide 29 · Thrombin is the central effector

Converts soluble fibrinogen into insoluble fibrin monomers.

Amplifies coagulation through factors V, VIII, and XI.

Activates factor XIII to cross-link fibrin.

Stimulates platelets and selected inflammatory cells through PAR signaling.

Slide 30 · Fibrin polymerization creates mechanical stability

Fibrinogen cleavage by thrombin

Fibrin monomer formation

Fibrin polymerization

Factor XIIIa cross-linking

A cross-linked fibrin mesh strengthens the initially fragile platelet aggregate.

Slide 31 · Thrombin coordinates clotting and inflammation

Hemostatic actions

Generates fibrin and activates factor XIII

Amplifies coagulation factors

Promotes platelet activation and aggregation

Cellular actions

Acts via protease-activated receptors

Activates endothelial and inflammatory responses

Contributes to repair-associated signaling

Slide 32 · PT and PTT interrogate laboratory pathways

Test

Principal pathway interrogated

Interpretive limit

PT

Tissue factor–initiated and common factors

Does not duplicate all in vivo reactions

PTT / aPTT

Contact-initiated and common factors

Contact system is less central in vivo

Slide 33 · Clotting must stay at the site of injury

Flow dilutes activated factors and allows their clearance by the liver.

Coagulation complexes require localized membrane phospholipid surfaces.

Intact adjacent endothelium expresses potent anticoagulant activities.

Fibrinolysis limits clot size and later assists resorption.

Slide 34 · Resting endothelium suppresses platelet activation

An intact monolayer separates platelets from subendothelial vWF and collagen.

Prostacyclin (PGI₂) and nitric oxide inhibit platelet activation.

Endothelial ADPase limits activation by degrading ADP.

These actions collectively prevent unnecessary platelet adherence.

Slide 35 · Endothelial proteins restrain coagulation

Regulatory axis

Main effect

Thrombomodulin + EPCR

Shift thrombin to protein C activation

Heparin-like molecules + antithrombin

Inhibit thrombin and activated factors

Tissue factor pathway inhibitor

Restrict TF–VIIa–dependent initiation

Slide 36 · Activated protein C inactivates cofactors

Thrombin binds thrombomodulin

Protein C binds EPCR and is activated

Activated protein C + protein S

Factors Va and VIIIa inhibited

Normal endothelium redirects thrombin from procoagulant to anticoagulant activity.

Slide 37 · Antithrombin and TFPI block amplification

Antithrombin

Activity enhanced by endothelial heparin-like molecules

Inhibits thrombin and factors IXa, Xa, XIa, XIIa

Basis for pharmacologic heparin action

Tissue factor pathway inhibitor

Endothelial anticoagulant regulator

Inhibits the tissue factor–VIIa pathway

Restrains propagation of TF-initiated coagulation

Slide 38 · Plasmin degrades fibrin

Plasminogen recruited to fibrin

T-PA promotes plasmin formation

Plasmin cleaves fibrin

Fibrin breakdown products

Fibrin-derived D-dimers indicate breakdown of cross-linked fibrin, but are not specific for a single cause.

Slide 39 · Fibrinolysis is spatially controlled

Endothelium produces tissue plasminogen activator (t-PA).

T-PA acts especially efficiently when associated with fibrin.

α₂-antiplasmin rapidly inhibits free plasmin.

Plasminogen activator inhibitors attenuate clot lysis.

Slide 40 · Endothelial activation reverses the balance

Resting endothelium

PGI₂, NO, ADPase suppress platelets

Protein C pathway, antithrombin, TFPI oppose coagulation

T-PA favors fibrinolysis

Activated or injured endothelium

Reduced thrombomodulin and anticoagulant activities

Procoagulant activation, tissue factor access

PAI release and reduced t-PA inhibit fibrinolysis

Slide 41 · Bleeding can reflect three distinct defects

Vessel wall defect

Platelet / vWF defect

Coagulation factor defect

Different defective components produce different anatomic patterns of hemorrhage.

Slide 42 · Primary hemostatic defects favor mucosal bleeding

Typical manifestations include petechiae and purpura.

Epistaxis, gastrointestinal bleeding, and heavy menstruation are characteristic.

Platelet number or function may be abnormal; VWF deficiency is another cause.

Very severe thrombocytopenia can cause catastrophic intracranial bleeding.

Slide 43 · Coagulation factor defects favor deep bleeding

Hematomas may develop in muscles and other soft tissues.

Hemarthrosis after minor trauma is characteristic of severe hemophilia.

Deep tissue bleeding reflects an inadequate stable fibrin clot.

Severe deficiencies can also produce intracranial hemorrhage.

Slide 44 · Vascular fragility produces purpura and bruising

Disorders of small vessels may produce palpable purpura.

Vasculitis and amyloidosis are examples of vascular disease.

Scurvy predisposes to vessel fragility.

Ecchymoses and soft tissue hematomas may occur without a primary factor deficiency.

Slide 45 · Bleeding morphology has useful terminology

Finding

Definition

Petechiae

Minute hemorrhages, typically 1–2 mm

Purpura

Larger skin / mucosal hemorrhages, ≥3 mm

Ecchymoses

Bruises measuring approximately 1–2 cm

Hematoma

Localized palpable collection of extravasated blood

Slide 46 · The bleeding pattern guides mechanism

Typical presentation

Most suggestive defect

Petechiae + epistaxis

Primary hemostasis / vessel wall

Hemarthrosis + muscle hematoma

Coagulation factor deficiency

Palpable purpura

Small-vessel inflammatory injury

Massive rupture-related bleed

Large-vessel structural failure

Slide 47 · Three variables determine hemorrhage severity

Volume of blood lost

Rate of blood loss

Anatomic location

A small intracranial bleed may be more dangerous than a larger superficial hemorrhage.

Slide 48 · Intracranial hemorrhage is a special emergency

The rigid skull limits accommodation of increased intracranial volume.

Rising pressure can compromise cerebral perfusion.

Severe hemorrhage can cause brainstem herniation.

Both platelet and coagulation defects can produce fatal intracranial bleeding.

Slide 49 · Chronic external bleeding depletes body iron

Repeated external blood loss

Loss of erythrocytes and their iron stores

Examples: Heavy menstruation, gastrointestinal bleeding

May cause iron deficiency anemia

Bleeding retained in tissues

Blood remains in body spaces or tissues

Iron can be recovered and recycled

Not equivalent to chronic external iron loss

Slide 50 · Hemostatic stress can unmask mild defects

Some bleeding tendencies are inconspicuous in everyday life.

Surgery, childbirth, dental work, menstruation, or trauma may reveal them.

Von Willebrand disease is a common inherited example.

Aspirin exposure and uremia are acquired causes of impaired platelet function.

Slide 51 · Thrombosis means pathologic intravascular clotting

A thrombus forms within intact blood vessels or cardiac chambers.

It differs from a localized hemostatic plug at a site of vascular injury.

Thrombi can obstruct blood flow or release emboli.

Arterial and venous thrombosis differ in their dominant pathophysiology.

Slide 52 · Virchow triad provides a causal framework

Endothelial injury / activation

Stasis or turbulence

Hypercoagulability

THROMBOSIS

Slide 53 · Endothelial injury promotes arterial thrombosis

Loss of endothelial integrity exposes vWF, collagen, and tissue factor.

Platelet adhesion is especially important under high-shear arterial flow.

Plaque rupture and vascular injury can trigger an arterial thrombus.

Inflammatory endothelial activation can be prothrombotic without overt denudation.

Slide 54 · Endothelial dysfunction is an active phenotype

Inflammation / disturbed flow / toxins

Endothelial gene-expression change

Less thrombomodulin / t-PA; More PAI

Greater local thrombogenicity

Endothelial activation links inflammatory and metabolic insults to clot formation.

Slide 55 · Laminar flow separates platelets from the wall

Physiologic laminar flow

Blood cells predominantly occupy a central stream

A plasma layer separates cells from the endothelium

Activated coagulation factors are diluted and washed away

Stasis or turbulence

Platelets contact the endothelium more readily

Activated factors accumulate locally

Endothelium may become activated or injured

Slide 56 · Stasis especially favors venous thrombosis

Immobility / impaired venous return

Slow blood flow

Reduced clearance of activated factors

Venous fibrin-rich thrombus

Turbulence is particularly important in arteries and the heart; Stasis is dominant in many veins.

Slide 57 · Common flow disturbances have specific settings

Hemodynamic problem

Illustrative setting

Turbulence

Atherosclerotic plaque; Stenotic arterial segment

Chamber stasis

Atrial fibrillation; Poorly contracting ventricle

Venous stasis

Prolonged bed rest; Reduced muscle pumping

Local stasis

Aneurysmal vessel dilation

Slide 58 · Hypercoagulability is a systemic predisposition

An increased tendency to clot is often caused by altered coagulation proteins.

Inherited thrombophilias include common variants and rare anticoagulant deficiencies.

Acquired states include immobilization, malignancy, surgery, pregnancy, and immune syndromes.

Hypercoagulability is particularly important in venous thrombosis.

Slide 59 · Factor V Leiden resists activated protein C

Factor V Leiden variant

Reduced factor Va inactivation by APC

Longer procoagulant cofactor activity

Increased venous thrombosis susceptibility

The mutation removes a natural anticoagulant feedback mechanism.

Slide 60 · Prothrombin G20210A increases substrate supply

Prothrombin 3′ UTR variant

Increased prothrombin levels

Greater thrombin-generating capacity

Venous thrombotic predisposition

Factor V Leiden and G20210A are distinct molecular mechanisms.

Slide 61 · Rare inherited defects affect anticoagulant brakes

Deficiency

Lost protection

Antithrombin

Inhibition of thrombin and activated factors

Protein C

Inactivation of activated cofactors Va and VIIIa

Protein S

Cofactor activity in anticoagulant pathways

Slide 62 · Genes and exposures act together

Underlying inherited predisposition

Additional acquired exposure

Combined prothrombotic pressures

Clinical thrombosis

An inherited variant alone does not imply that thrombosis is inevitable.

Slide 63 · Acquired thrombophilia has multiple mechanisms

Setting

Major mechanistic emphasis

Immobilization / heart failure

Stasis

Surgery / fracture / burns

Injury, tissue procoagulants, inactivity

Pregnancy / oral contraception

Hormonal shifts toward coagulation

Disseminated malignancy

Tumor-related procoagulants, inflammation

Slide 64 · Cancer can provoke systemic thrombosis

Some malignancies release tissue factor or other procoagulants.

Tumor-associated inflammation contributes to hypercoagulability.

Disseminated cancer can be associated with migratory thrombophlebitis.

Trousseau syndrome exemplifies the association between cancer and thrombosis.

Slide 65 · Heparin-induced thrombocytopenia is immunologic

Heparin + platelet factor 4 complexes

Anti-PF4/heparin IgG

Fc receptor–mediated platelet activation

Thrombocytopenia + thrombosis

Despite falling platelet counts, platelet activation generates substantial thrombotic risk.

Slide 66 · HIT: Platelet count and thrombosis diverge

Why platelets fall

IgG-containing complexes activate platelets

Antibody-coated activated platelets are removed

Thrombocytopenia is common

Why clotting rises

Activated platelets express procoagulant surfaces

Venous and arterial thrombosis can occur

Recognition depends on a compatible syndrome and anti-PF4 testing

Slide 67 · VITT shares PF4 autoimmunity, not heparin exposure

Vaccine-induced thrombotic thrombocytopenia has been described rarely after certain adenoviral-vector COVID-19 vaccines.

Antibodies against PF4 are involved, without requiring exposure to heparin.

Thromboses may affect cerebral venous sinuses and other venous territories.

The source describes this as a very rare but potentially life-threatening syndrome.

Slide 68 · Antiphospholipid syndrome combines thrombosis and obstetric disease

Antiphospholipid antibodies are associated with venous or arterial thrombosis.

Pregnancy manifestations include repeated losses and other placental complications.

APS may be primary or accompany systemic autoimmune disease, especially SLE.

Antibody positivity alone does not establish the full clinical syndrome.

Slide 69 · APS pregnancy morbidity is not purely thrombotic

Early fetal loss

Interference with trophoblast growth and differentiation

Impaired placentation may be central

Not fully explained by placental vascular thrombosis

Later obstetric complications

Trophoblast dysfunction remains relevant

Inflammatory and complement pathways also contribute

Preeclampsia and preterm birth can occur

Slide 70 · Why “lupus anticoagulant” is misleading

In vitro observation

Antiphospholipid antibodies can prolong PTT

They interfere with phospholipid-dependent assays

The historic term “anticoagulant” reflects laboratory testing

In vivo clinical phenotype

Patients may have a prothrombotic state

Thrombosis and pregnancy morbidity define the clinical risk

Interpret assays with the clinical context

Slide 71 · Thrombi contain components of flowing blood

Thrombi contain platelets, fibrin, erythrocytes, and degenerating leukocytes.

Their relative proportions depend on flow conditions and location.

They are attached to the vascular or endocardial surface where they originate.

Propagation may create an unstable trailing segment.

Slide 72 · Lines of Zahn signify formation during flow

Pale platelet + fibrin layers

Darker erythrocyte-rich layers

Original schematic — not histology

Slide 73 · Plaque disruption initiates an arterial thrombus

Arterial flow

Platelet/fibrin-rich thrombus

Atherosclerotic plaque

Original vascular schematic — not a gross or histologic specimen

Slide 74 · Arterial thrombi commonly relate to endothelial injury

Arterial thrombi are frequently occlusive.

Ruptured or eroded atherosclerotic plaques commonly provide the substrate.

Platelets and fibrin are prominent in these higher-flow environments.

Coronary, cerebral, and femoral arterial beds are common sites.

Slide 75 · A venous thrombus may fill the entire lumen

Slow venous flow

RBC-rich luminal thrombus

Venous wall

Original vessel schematic — not a gross or histologic specimen

Slide 76 · Venous thrombi are typically red and occlusive

Venous thromboses often form elongated casts of the venous lumen.

Sluggish flow favors extensive entrapped red cells with relatively fewer platelets.

These are called red or stasis thrombi.

Deep veins of the lower extremities are common sites.

Slide 77 · Mural thrombi adhere to the heart or aorta

Cardiac mural thrombi

Develop at abnormal endocardial surfaces

Promoted by myocardial infarction, dyskinetic contraction, and arrhythmia

Can give rise to systemic emboli

Aortic mural thrombi

May accompany aneurysmal dilatation

Atherosclerotic ulceration contributes injury and turbulence

Can provide a source of embolic fragments

Slide 78 · Antemortem thrombus versus postmortem clot

Characteristic

Antemortem thrombus

Postmortem clot

Wall attachment

Usually present

Usually absent

Texture

Typically firmer

Gelatinous

Lamination

Lines of Zahn may appear

Generally not laminated

Appearance

Flow-associated layering

Red dependent + yellow “chicken fat”

Slide 79 · Valve vegetations are thrombotic masses

Vegetations are thrombi that form on cardiac valves.

Infective endocarditis creates microbial-associated, thrombotic masses.

Nonbacterial thrombotic endocarditis may occur in hypercoagulable states.

Libman–Sacks vegetations may accompany systemic lupus erythematosus.

Slide 80 · Propagation and flow direction matter

Arterial thrombi

Often begin at injury or turbulence

May extend retrograde relative to local blood flow

Growth generally proceeds toward the heart

Venous thrombi

Typically originate in stasis-prone segments

Propagate in the direction of venous flow

Poorly attached regions may detach and embolize

Slide 81 · Four possible fates of a thrombus

Propagation

Embolization

Dissolution

Organization ± recanalization

These outcomes may coexist in a single evolving thrombus.

Slide 82 · Clot age influences fibrinolytic dissolution

Recent thrombi may be largely dissolved through fibrinolysis.

Older thrombi accumulate dense, cross-linked fibrin.

Established organized thrombi are less susceptible to dissolution.

This distinction underlies the importance of timing in thrombolytic therapy.

Slide 83 · Organization converts thrombus into tissue

Endothelial + fibroblast ingrowth

Granulation-like organization

Capillary channel formation

Partial recanalization / fibrosis

Recanalization may restore part of the lumen, but not necessarily normal vessel structure.

Slide 84 · Arterial and venous thrombi create different hazards

Arterial / cardiac thrombi

Critical-artery occlusion causes tissue ischemia

Consequences include myocardial and cerebral infarction

Detached material may cause systemic emboli

Deep venous thrombi

Obstruction produces venous congestion and edema

Deep thrombi may be clinically silent

Embolization can lead to pulmonary embolism

Slide 85 · Deep vein thrombosis may be clinically silent

Leg DVT can cause swelling, pain, or tenderness.

Collateral venous channels may limit obvious local symptoms.

The source notes that many DVTs are asymptomatic until embolization.

Immobility, cardiac failure, surgery, pregnancy, and cancer raise susceptibility.

Slide 86 · Disseminated intravascular coagulation consumes factors

Systemic thrombin activation

Widespread microvascular fibrin thrombi

Platelet / factor consumption

Bleeding + organ dysfunction

DIC is a secondary syndrome, not one specific primary disease.

Slide 87 · Case: Epistaxis, petechiae, and heavy menses

A patient develops frequent epistaxis, petechiae, and excessive menstrual bleeding after minor hemostatic stresses.

Which hemostatic compartment is most likely involved?

Mechanistic interpretation

Primary hemostasis—platelet number/function or vWF-dependent adhesion. The bleeding distribution is more informative here than any single molecular diagnosis.

Slide 88 · Case: Spontaneous knee hemarthrosis

A young patient has recurrent bleeding into the knee joint after minimal trauma but lacks prominent petechiae.

What kind of defect should be considered first?

Mechanistic interpretation

A coagulation factor deficiency affecting secondary hemostasis. Hemarthrosis is a characteristic deep-bleeding pattern.

Slide 89 · Case: Thrombosis despite thrombocytopenia

Following heparin exposure, platelet counts decrease and the patient develops a new venous thrombus.

What mechanism links low platelet count to new thrombosis?

Mechanistic interpretation

Immune platelet activation by anti-PF4/heparin antibodies can cause both platelet consumption and a strong procoagulant state.

Slide 90 · Case: Prolonged immobility and a leg thrombus

A hospitalized patient develops a proximal leg venous thrombosis after prolonged immobilization.

Which Virchow component is especially important?

Mechanistic interpretation

Venous stasis: Reduced muscle pumping and slow flow limit the washout of activated coagulation factors; Other factors may also contribute.

Slide 91 · Integrate bleeding pattern with the failed step

Impaired step

Clue

Mechanistic interpretation

Platelet adhesion / function

Mucocutaneous bleeding

Poor primary plug formation

Factor-generated fibrin

Deep tissue / joint bleeding

Unstable secondary plug

Vascular integrity

Palpable purpura / ecchymoses

Fragile or inflamed vessel wall

Systemic coagulation activation

Thrombosis plus bleeding

Consumptive coagulopathy

Slide 92 · A compact mechanism map of thrombosis

Endothelial injury / dysfunction

Abnormal flow and local stasis

Inherited / acquired procoagulant bias

Platelet + fibrin thrombus

Virchow triad components interact; The dominant contribution depends on the vascular bed.

Slide 93 · What a thrombus can ultimately do

Local growth / propagation

Vascular obstruction

Fragmentation / embolization

Organization / dissolution

The dominant clinical consequence depends on location, vascular supply, and embolization.

Slide 94 · Integrated core principles

Normal hemostasis requires a platelet plug, thrombin-mediated fibrin, and endothelial containment.

Mucosal versus deep-tissue bleeding suggests different failing components.

Thrombosis results from injury, abnormal flow, hypercoagulability, or their combination.

Thrombus morphology and location predict obstruction, embolization, and remodeling.

Slide 95 · Principal source and coverage

Robbins, Cotran & Kumar: Pathologic Basis of Disease

11th edition (2026)

Hemostasis, Hemorrhagic Disorders, and Thrombosis

Coverage: normal hemostasis, bleeding disorders, and thrombosis

Figures are original, editable conceptual schematics; no textbook images reproduced.