Hyperemia

Hyperemia (congestion) is a condition in which capillaries are dilated and filled with blood.

Hyperemia in the oral cavity

Physiological hyperemia[edit | edit source]

Blood vessels that are normally closed at rest open and dilate or leak only plasma (vasa serosa).
This is a purely functional phenomenon occurring, for example, in working skeletal muscle.

Peristatic

Occurs in the vicinity of inflammation, when mediators (e.g. histamine) are released from damaged cells, causing maximal dilation of capillaries without corresponding opening of arterioles.
Blood flow slows to a halt (peristasis) and erythrocytes fill the entire capillary, widening the interstices between the endothelium and allowing extravascular penetration of fluid with proteins (exudation) and blood cells (infiltration).

Venostatic (passive)

Capillaries become engorged with blood when blood outflow through veins is restricted (oppression of a vein by tumors, thrombosis). This leads to an increase in hydrostatic pressure and transudation of fluid without protein (unlike inflammation, there are no mediators to cause opening of interstitial clefts in the capillary wall);
So-called venostatic oedema occurs (e.g. ascites in portal hypertension conditioned by hepatic vein thrombosis);
If the blood flow stops (congestion - venostasis), the relevant tissue undergoes hypoxemic necrosis, which is referred to as hemorrhagic infarction (e.g. in small bowel in thrombosis of the portal vein. However, a hemorrhagic infarction of the intestine in mesenteric artery thromboembolism will have the same picture);
Necrosis is healed by fibrosis with stiffening of the organ - called induction;
Organs are dark purple in venostasis (cyanotic induction, e.g. spleen in right-sided heart failure). An exception is the lung, in which congestion in left-sided heart failure takes the form of rust induction (erythrocyte breakdown extravascularly and the production of hemosiderinu, which is phagocytosed by alveolar macrophages).

Hyperemic effects can be targeted primarily by:

PASTOR, John. Langenbeck's medical web page [online]. [cit. 2009-09-01]. <https://langenbeck.webs.com/>.