DMD 24. Introduction to Circulatory Disorders

Learning Outcomes

By the end of the lecture, you should be able to:

• Describe vascular insufficiency and define key terms:

  • Ischaemia: Impaired blood flow or perfusion to tissues, leading to nutrient deprivation.

  • Infarction: Tissue death due to ischaemia.

• List the main causes of ischaemia.

• Describe thrombosis and Virchow’s triad.

• Define embolus and describe the implications of thrombo-embolic events.

Importance of Circulatory Disease

• Significance:

  • Major cause of morbidity and mortality.

  • Poses a massive burden on the NHS.

• Dental Implications:

  • Patients with circulatory issues may require special dental considerations.

Key Terms to Know

• Ischaemia/ Vascular Insufficiency -Vascular occlusion leading to decreased blood flow. ischaemia - Impaired blood flow depriving tissues of oxygen/nutrients

• Infarction -Cell death (necrosis) resulting from ischaemia

• Haemostasis

• Thrombosis -A solid mass of blood constituents formed in the vascular system during life

• Embolism -blockage of a blood vessel by a foreign substance, such as a blood clot,

• Atheroma -a fatty deposit that builds up in the walls of arteries

Normal Circulation

• Vascular System:

  • Comprises the heart and vessels, delivering blood to organs/tissues and returning it to the heart.

• Lymphatic System:

  • Passive drainage system that returns extracellular fluid to the vascular system.

Anatomy of Blood Vessels

1. Tunica Intima

   • Endothelium, subendothelium, internal elastic lamina.

2. Tunica Media

   • Smooth muscle layer, external elastic lamina.

3. Tunica Adventitia

   • Composed of collagen 1, vasa vasorum, nervi vasorum.

Complications of Blood Vessels

• Issues:

  • Blocked or occluded (internally, externally, within the wall).

  • Dilated

  • dissected/ruptured

  • inflamed

  • abnormal growths (tumors hemangioma, congenital defects)-present from birth

Vascular Insufficiency

• Definition: Vascular occlusion leading to decreased blood flow.

• can affect both arterial and venous structure

• effects depends on tissue involved, rate of occlusion, collateral blood suppy present

• Ischaemia: - progressive occulsion, reversible

  • Impaired blood flow depriving tissues of oxygen/nutrients

  • may be reversible based on duration and metabolic demands of the tissye

Infarction - irreversible

• Definition:

  • Cell death (necrosis) resulting from ischaemia; effects are irreversible and tissues vary in their repair abilities. elicit an inflammatory response

Appearance of Infarcts

• Types of Infarcts:

  • Red Infarcts:

    • Caused by venous occlusion, found in loose tissues (e.g., lung), and areas with dual circulation.(lung and liver)

  • Pale (White) Infarcts:

    • Usually occur in solid organs (e.g., heart, spleen, kidney) with single blood supply.

Causes of Ischaemia/Vascular Insufficiency

• Factors Leading to Ischaemia:

  • Vascular blockage, the occlusion of varying locations (internally, externally, or within the wall).

  • Irreversible infaction depends on and pattern of occlusion, collateral blood supply, tissue vulnerability to hypoxia.

  • 

Thrombus Formation

• Definition:

  • A solid mass of blood constituents formed in the vascular system during life

  • Thrombus formed of alternating layer of platelet, fibrin and RBC

  • on damage endothelial wall with a platelet plug

  • grow in the direction of blood flow

  • pale deposit - platelet

  • dark deposit - dark

  • Lines of Zahn - alternating bands

  • Embolus can cause renal infaction

    

• Distinction from Clots:

  • Clot: solid mass occurring outside the vascular tree or after death

Virchow’s Triad - 3 predisposing factors

• Components:

  1. Changes in the intimal surface of the vessel. (endothelial injury)

  2. Changes in blood flow pattern (e.g., turbulence, stasis).

  3. Changes in blood constituents (e.g., hypercoagulability).

• arteries - atheroma

• veins - stasis venous return

Changes to Endothelial Surface

• Intima is only one cell thick, usually resist thrombus formation → damage expose extracellar matrix proteins and glycoprotein → inducing thrombosis

• Factors Causing Damage:

  • Haemodynamic forces, hyperlipidemia (fat build up in artery) , cigarette smoke, immune complex deposition, infections, trauma, chemicals, infarction.

Changes in Blood Flow

• Turbulence in arteries and stasis in veins contribute to thrombus formation.

Changes in Blood Constituents

• Condition:

  • Blood may have increased susceptibility to coagulation (hypercoagulable state). By increase coagulation protein, platelet aggregation. Decreae anti thrombotic

  • seen in conditions like

  • polycythaemia - increase RBC

  • Burns - loss of plasma

  • thrombocythaemia - increase platelet

  • Myeloma - increase plasma protein in bone marrow

Clinical Implications of Thrombosis

• Effects:

  • Variability influenced by the vascular system involved, speed of development, collateral flow availability, and tissue sensitivity to ischaemia.