essay 4 = disorders of peripheral circulation arterial and venous hyperemia, ischemia, infarction. thrombosis and embolism

what is arterial hyperemia

• increased inflow of arterial blood with normal outflow of venous blood.

• It is characterised by increased blood flow due to tissues being more active than normal, with local arterioles responding by dilating

• It can be physiologic such as during physical activity, emotional blushing or menopausal hot flashes

• Can also be pathologic, in case of inflammatory, allergic and burn reactions

what does the areas affected by arterial hyperemia look like

1. impaired venous outflow

2. blood backs up on the venous side of circulation and hydrostatic pressure in the venules and capillaries increases

3. the vessels overfill with deoxygenated blood leading to tissue hypoxia

4. tissues becomes blue and cold

what is ischemia

• insufficient blood flow to a specific area, leading to decreased oxygen levels, nutrient delivery and waste removal

• caused by vasoconstriction, external compression and arterial occlusion

• the symptoms are paleness, decreased size and decreased temperature of the affected organ

• prolonged ischemia leads to necrosis and infarction

what is infarction

• tissue necrosis caused by a prolonged lack of oxygen supply to the affected organ

• there are two types:

1. White infarction - anemia

— affects solid organs e.g spleen, heart kidney

— caused by arterial occlusion

— infarcts appear pale without significant bleeding into necrotic tissue

2. red infarction - hemorrhagic

— affects soft tissues e.g brain, lungs

— caused by venous occlusion

— infarcts appear red due to blood pooling or re-entry into necrotic tissue

what is thrombosis

• pathological formation of blood clots within vascular system causing an obstruction of blood flow.

• The causes of thrombosis are explained using virchows triad:

1. endothelial injury

2. changes in blood flow

3. changes in blood composition

process of thrombosis

1. platelets adhere to endothelium and to each other

2. blood flow has slowed, the RBC are entangled causing an occlusion of the blood vessel lumen

3. coagulation and precipitation of plasma proteins

what is embolism

• obstruction of a vessel by material that has entered and traeled in the circulation.

• Types of embolus (the material) = air, gas, fat, thrombus, atherosclerotic plaque, tumor cells and amniotic fluid

types of embolism based on its path is

• orthograde = follows blood flow

• retrograde = against the blood flow

• paradoxical = embolus from the venous circulation crosses into the arterial circulation through an abnormal opening (such as a patent foramen ovale or atrial septal defect), leading to systemic embolism