Hyperaemia

Hyperaemia is due to opening of new capillary and collection of blood in capillaries of tissue of any part of the body where as congestion is accumulation of blood in small vessels like venules or arteriols . hyperaemia may be divided in to active and passive types –

i)                    Active hyperaemia – Due to the dilation of both arteriols and capillaries , there will be an increased blood flow in a particular area . hyperaemia in inflammation is best example . The features of active hyperaemia is the part will be warm , bluish – red in colour , swollen , the capillaries aree dialated and engorged .

ii)                  Passive hyperaemia -  This is also called passive venous congestion . it is due to the stragnation of blood . here , the blood flow ;will be slow , the part will be purpe in coour and cold due to the less incoming of arterial blood . passive hyperaemia may be-

a)      Local -  It may be due to the obstruction in the venouis passage and it may be-

i)                    Acute obstruction -  A thrombus or an embolus may occlude the venous passage . Voilvulus and twisting of pedicle of an ovarian tumour may cause acute obstruction .

ii)                  Chronic local venous congestion -  Due to portal obstruction , there will be congestion in liver .

b)      General -  It is du8e to difficulty in venous to the central area like cardiac and pulmonary area . It may be due to –

i)                    Acyute passive venous congestion – It is found in pulmonary oedema due to left ventricular failure .

ii)                  Chronic generalized passive hyperaemia – It is found in congestive cardiac failure .