Pathology 2420A Study Guide - Final Guide: Pulmonary Embolism, Oncotic Pressure, Myocardial Infarction
22 Jul 2018
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Final Exam Objectives
Module 6-12
Module 6 Objectives:
1. Understand basic principles of fluid balance and be familiar with edema both local and
generalized, i.e. definition, mechanisms, causes and effects of each.
• Starlings Law
▪ HYDROSTATIC PRESSURE- in vessel which measures, 32mmHg at
arterial end, 12mmHg at venous end
▪ Oncotic pressure- colloid osmotic pressure (COP) of plasma (26mmHg)
which reflects the amount of serum protein (albumin)
▪ Interstitial fluid pressure- tissue tension, 3-4mmHg
▪ Tissue (interstitial) fluid OSMOTIC PRESSURE- very low, amount
leaking vessel
o Edema- accumulation of abnormal/excess fluids in the interstitial/intracellular
tissue, leading to swelling of the subcutaneous tissues
o Edema will occur when: an increase in hydrostatic pressure, fall in COP,
lymphatic obstruction, sodium retention
o Local Edema
▪ Occurs due to:
▪ Increase in hydrostatic pressure due to local vascular obstruction
▪ Lymphatic obstruction: compression by tumour or inflammation (local)
o Generalized Edema
▪ Reflects a global disorder of fluid or electrolyte metabolism
▪ Occurs due to:
▪ Increase in hydrostatic pressure, e.g heart failure, severe cirrhosis where
blood is blocked from the liver (portal hypertension, increased hydrostatic
pressure)
▪ Decreased COP due to: loss of serum albumin and proteins in renal
failure, decreased synthesis of albumin (liver failure or cirrhosis), loss of
serum proteins due to malnutrition
▪ Sodium retention (increased blood volume), e.g. kidney disease
2. Understand the basic principles of thrombosis, i.e. definition, mechanisms, causes and
effects.
• Thrombosis is a formation of a mass within the heart or blood vessels, adherent to the
vascular endothelium
o Clotted blood- coagulated blood containing platelets, fibrin, RBC, WBC
o THROMBUS IN DEEP VEINS OF THE LEG HAVE AN INCREASED RISK
OF PULMONARY EMBOLISM
o Causes:
▪ Vessel wall damage/alteration as a result of injury (tear), inflammation,
atherosclerosis
▪ Changes in blood flow due to: turbulence (in aneurysm or at site of arterial
branching), stasis (slow of circulation) because of lack of activity,
decreased cardiac output, increased blood viscosity
▪ Changes in blood composition: an increase in platelets
o Prognosis:
▪ Dissolve or be lyzed by fibrinolytic activity (won’t obstruct)
▪ Increase in size and obstruct vessels
▪ Breakdown and form emboli (causes death if blocks arteries)
▪ May cause less blood flow but not fully block an artery
o Most commonly affect vessels:
▪ Coronary artery- heart attack (MI)
▪ Cerebral artery- stroke
▪ Mesenteric arteries- kidney infarct
▪ Arteries of the leg- gangrene
3. Become familiar with the types of embolism and know their effects.
• Embolism- occlusion of blood vessel by a mass and is TRANSPORTED TO THE SITE
through the blood stream
o Sources:
▪ Large majority of pulmonary emboli (90%) arise from the deep veins of
the legs
▪ The heart is the most common source of arterial emboli (usually from
thrombi on the heart walls or from diseased valves); they lodge in the
brain (cause infarction and stroke)
o Types:
▪ Formed from thrombi (may be termed a thromboembolus)
▪ Gas (air)= gas bubbles in divers (Bend’s disease)
▪ Fat= often after fracture of large bones
▪ Tumor
▪ Others= foreign body (drug addicts); clumps of bacteria in severe bacterial
infections (septic emboli), amniotic fluid
4. Know the difference between a thrombus and an embolus.
• Thrombus- mass formed WITHIN a blood vessel
o Embolus- mass that TRAVELS through the CIRCULATION and becomes lodged
in a blood vessel
5. Know the causes and effects of ischemia.
• Ischemia:
▪ Due to: inadequate blood supply to an area of tissue
▪ Result is: infarction- area of necrosis (death) produced by ischemia
(usually after occlusion of an artery)
o Causes:
▪ Decreased blood supply: inadequate cardiac output
▪ Can be due to obstruction of blood vessel by: thrombus, embolus,
pressure, damage of vessel wall (inflammation)
o Effects:
▪ Depends on degree of ischemia
▪ No effects if there is alternate or collateral blood supply
▪ Tissue death (infarction) if infarct is severe and complete
• Define hemorrhage and define and describe the various types
• Hemorrhage- a discharge or escape of blood from the blood vessels into surrounding
tissues, the exterior of the body or into a body cavity
o Causes:
▪ Trauma, surgical procedures, weakened artery (from atheroscleriosis, e.g.
abdominal aorta), infections (e.g. pulmonary TB), invasive tumours
(erosion of vessel wall)
o Definitions:
▪ Hematoma- bleeding into the soft tissues
Document Summary
Increase in hydrostatic pressure due to local vascular obstruction: lymphatic obstruction: compression by tumour or inflammation (local, generalized edema, reflects a global disorder of fluid or electrolyte metabolism, occurs due to: Atherosclerosis begins early in life and remains clinically silent until it has progressed to the point where it results in disease. The earliest pathological lesion is called a fatty streak. Some fatty streaks slowly progress into mature atherosclerotic lesions (fibro fatty plaque): plaque development is a result from chronic inflammatory response resulting from injury to the endothelial lining of the artery. Many atherosclerotic risk factors act by contributing to some form of endothelial damage. The damage results in endothelial dysfunction, which allows for platelets and monocytes to adhere to the lining. These elements release various growth factors and cytokines which recruits the migration of smooth muscle cells and fibroblasts into the endothelium. Macrophages engulf lipids and cholesterol from the blood.
