PATHO CHAPTER 22

CHAPTER 22

What is hemostasis?

Stopping bleeding after vessel injury while keeping blood flowing elsewhere.

4 steps of hemostasis?

Vessel spasm → platelet plug → coagulation cascade → fibrin clot

Thrombosis = ?

Inappropriate clot in vessel

What is a bleeding disorder?

Failure to form an adequate clot after an appropriate injury/stimulus.

What is the purpose of vessel spasm?

Vasoconstriction → ↓ blood flow

What happens during platelet activation?

Platelets change from smooth discs to spiny spheres + expose receptors

What are the 3 key platelet-plug steps?

Activate → adhere → aggregate

What does von Willebrand factor (vWF) help platelets do?

Helps platelets stick to injured vessel

Needed for normal clotting?

Platelets + vWF + clotting factors + vitamin K

Both intrinsic + extrinsic pathways meet where?

Factor X/common pathway

What converts prothrombin to thrombin?

Prothrombin activator

Thrombin converts what?

Converts Fibrinogen → fibrin

Fibrin does what?

Forms an insoluble mesh → Stabilizes clot

Antithrombin III does what?

Inactivates thrombin/clotting factors

How does heparin affect antithrombin III?

Speeds up antithrombin III

What does protein C do?

Inactivates factors V + VIII → limit clotting

What does protein S do?

Helps protein C work

Plasmin does what?

Breaks down fibrin/clot

Arterial clot usually caused by?

Turbulent flow + platelet adhesion

Venous clot usually caused by?

Stasis + clotting factors

VTE risk factors?

Pregnancy + OCPs + surgery + immobility + CHF + cancer

Atherosclerosis causes clots how?

Endothelial injury → platelet adhesion → thrombus

Signs of platelet deficiency?

Petechiae + purpura + mucosal bleeding

Petechiae = ?

Tiny purple-red bleeding spots (small-vessel bleeding)

Purpura = ?

Purple bruising areas (under skin)

Thrombocytopenia = ?

↓ platelets

Causes of thrombocytopenia?

↓ production + ↑ destruction + spleen sequestration

A patient has low platelets and new petechiae. What is the priority concern?

Bleeding/hemorrhage risk.

Why does vitamin K deficiency cause bleeding?

The liver cannot make fully active clotting factors

Hemophilia A = ?

Factor VIII deficiency

Hemophilia B = ?

Factor IX deficiency

Von Willebrand disease = ?

↓/defective vWF → poor platelet adhesion + ↓ factor VIII

Scurvy causes bleeding how?

↓ vitamin C → weak collagen → fragile vessels

Why does Cushing disease cause easy bruising?

Excess cortisol causes protein wasting and weak vessel support

DIC = ?

Widespread clotting → uses factors/platelets → bleeding

Common DIC triggers?

Sepsis + shock + trauma + surgery + cancer + obstetric problems

Why can DIC cause both thrombosis and bleeding?

Factors used up making clots → cannot clot later

Image recall: What is the final clot pathway?

→ Factor X/V + Ca²⁺ + platelet phospholipids → prothrombin activator → thrombin → fibrinogen to fibrin clot.