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15 results found

Intracranial aneurysm (overview)

Intracranial aneurysms, also called cerebral aneurysms, are aneurysms of the intracranial arteries. The most common morphologic type is the saccular aneurysm. Pathology There is not a universal classification for the types of intracranial aneurysms, resulting in a heterogeneous mix of terms ba...

Antineutrophil cytoplasmic antibody

Antineutrophil cytoplasmic antibodies (ANCAs) are a heterogenous class of IgG autoantibodies raised against the cellular contents of neutrophils, monocytes and endothelial cells 1. Under indirect immunofluorescence (IIF) microscopy, three ANCA staining patterns are observed, based on the varying...


Congestion is a pathological term referring to reduced blood flow out from tissues, which may be localized or systemic 1. Clinical presentation Congestion commonly presents with increased swelling and edema of tissues where blood flow is reduced. With prolonged congestion, the tissues may beco...

Angiotensin converting enzyme

Angiotensin converting enzyme (ACE) is a central component of the renin-angiotensin system (RAS) which assists in blood pressure control by regulating the volume of fluids in the body. Normal individuals may have a small volume of the angiotensin converting enzyme circulating in their blood. M...

Starling forces

Starling forces describe the movement of fluids between the vasculature and interstitial spaces. Fluid movement is determined by the balance of hydrostatic and osmotic pressure gradients 1. Starling forces Net pressure = [ (Pc - Pi) - (pc - pi) ] where: Pc = hydrostatic pressure of the capil...


Lymph (also known as lymphatic fluid) is the name given to the interstitial fluid once it has passed into the lymphatic vessels. Formation As blood passes through capillary beds a significant proportion of the plasma is filtered into the extracellular space. Most of this filtered tissue fluid ...

Hernia (general)

Hernias (or herniae) are a common pathological entity, in which an anatomical structure passes into an abnormal location via an opening. The opening may be a normal physiological aperture (e.g. hiatus hernia: stomach passes through the diaphragmatic esophageal hiatus) or pathological. Iatrogeni...


Alpha-fetoprotein (AFP) is an important plasma protein synthesized by the yolk sac and fetal liver. In adults, its main utility is as a tumor marker, primarily for hepatocellular carcinoma or teratoma. Functionally it is the fetal homologue of albumin i.e. it acts as a major carrier protein in t...


A fistula (plural: fistulae or fistulas) is an abnormal connection between two epithelial surfaces such as between hollow organs, skin or vessels. Conventionally, the name of a specific fistula type is a combination of the two organs. For discussions of specific fistulae please refer to individu...


Hematomas (alternative plural: hematomata) are the name given to localized collections of blood and they can form virtually anywhere in the body. They often form secondary to trauma or surgery but spontaneous formation is also not uncommon, especially in those with coagulation disorders or on an...


Lipohyalinosis (also known as fibrinoid necrosis) is a disease affecting the small cerebral arteries associated with lacunar infarction and deep white matter changes related to small vessel chronic ischemia. Pathology The histopathological landmarks of lipohyalinosis are irregular fibrosis and...

Liquefactive necrosis

Liquefactive necrosis is a form of necrosis where there is transformation of the tissue into a liquid viscous mass. Pathology In liquefactive necrosis, the affected cell is completely digested by hydrolytic enzymes leading to a soft, circumscribed lesion which can consist of fluid with remains...

Histology of blood vessels

Blood vessels, namely arteries and veins, are composed of endothelial cells, smooth muscle cells and extracellular matrix (including collagen and elastin). These are arranged into three concentric layers (or tunicae): intima, media and adventitia. the intima (or tunica intima) inner layer abut...

Intracranial arteries

Intracranial arteries have a unique structure when compared to extracranial vessels of similar size: see general histology of blood vessels entry. Proximal larger arteries The proximal arteries, arising from the internal carotid and vertebral arteries have differing distribution of elastic fib...


Aneurysms are focal abnormal dilatation of a blood vessel. They typically occur in arteries; venous aneurysms are rare. Aneurysms may also occur in the heart. Pathology Pathological types true aneurysm false aneurysm (or pseudoaneurysm) Etiology Atherosclerotic atherosclerosis Non-athero...

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