An exudate is a fluid released by an

organism An organism is any life, living thing that functions as an individual. Such a definition raises more problems than it solves, not least because the concept of an individual is also difficult. Many criteria, few of them widely accepted, have be ...

through pores or a wound, a process known as exuding or exudation. ''Exudate'' is derived from ''exude'' 'to ooze' from

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

'to (ooze out) sweat' (' 'out' and ' 'to sweat').

Medicine

An exudate is any

fluid In physics, a fluid is a liquid, gas, or other material that may continuously motion, move and Deformation (physics), deform (''flow'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are M ...

that filters from the

circulatory system In vertebrates, the circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the body. It includes the cardiovascular system, or vascular system, that consists of the heart ...

into lesions or areas of

inflammation Inflammation (from ) is part of the biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. The five cardinal signs are heat, pain, redness, swelling, and loss of function (Latin ''calor'', '' ...

. It can be a pus-like or clear fluid. When an injury occurs, leaving skin exposed, it leaks out of the blood vessels and into nearby tissues. The fluid is composed of serum, fibrin, and leukocytes. Exudate may ooze from cuts or from areas of infection or inflammation.

Types

* Purulent or suppurative exudate consists of plasma with both active and dead neutrophils, fibrinogen, and necrotic parenchymal cells. This kind of exudate is consistent with more severe infections, and is commonly referred to as pus. * Fibrinous exudate is composed mainly of fibrinogen and fibrin. It is characteristic of rheumatic carditis, but is seen in all severe injuries such as

strep throat Streptococcal pharyngitis, also known as streptococcal sore throat (strep throat), is pharyngitis (an infection of the pharynx, the back of the throat) caused by ''Streptococcus pyogenes'', a Gram-positive bacteria, gram-positive, group A str ...

and bacterial pneumonia. Fibrinous inflammation is often difficult to resolve due to blood vessels growing into the exudate and filling space that was occupied by fibrin. Often, large amounts of antibiotics are necessary for resolution. * Catarrhal exudate is seen in the nose and throat and is characterized by a high content of mucus. * Serous exudate (sometimes classified as serous transudate) is usually seen in mild inflammation, with relatively low protein. Its consistency resembles that of serum, and can usually be seen in certain disease states like

tuberculosis Tuberculosis (TB), also known colloquially as the "white death", or historically as consumption, is a contagious disease usually caused by ''Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can al ...

. (See below for difference between transudate and exudate) * Malignant (or cancerous) pleural effusion is effusion where cancer cells are present. It is usually classified as exudate. Types of exudates: serous, serosanguineous, sanguineous, hemorrhaging and purulent drainage. *Serous: Clear straw colored liquid that drains from the wound. This is a normal part of the healing process. *Serosanguineous: Small amount of blood is present in the drainage; it is pink in color due to the presence of red blood cells mixed with serous drainage. This is a normal part of the healing process. *Sanguineous: This type of drainage contains red blood due to trauma of blood vessels, this may occur while cleaning the wound. Sanguineous drainage is abnormal. *Hemorrhaging: This type of drainage contains frank blood from a leaking blood vessel. This will require emergency treatment to control the bleed. This type of drainage is abnormal. *Purulent drainage: This type of drainage is malodorous and can be yellow, gray, or greenish in color. This is an indication of an infection.

Exudates vs. transudates

There is an important distinction between transudates and exudates. Transudates are caused by disturbances of hydrostatic or

colloid osmotic pressure Oncotic pressure, or colloid osmotic-pressure, is a type of osmotic pressure induced by the plasma proteins, notably albumin, in a blood vessel's plasma (or any other body fluid such as blood and lymph) that causes a pull on fluid back into ...

, not by inflammation. They have a low protein content in comparison to exudates. Medical distinction between transudates and exudates is through the measurement of the

specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

of extracted fluid. Specific gravity is used to measure the protein content of the fluid. The higher the specific gravity, the greater the likelihood of

capillary A capillary is a small blood vessel, from 5 to 10 micrometres in diameter, and is part of the microcirculation system. Capillaries are microvessels and the smallest blood vessels in the body. They are composed of only the tunica intima (the inn ...

permeability changes in relation to body cavities. For example, the specific gravity of the transudate is usually less than 1.012 and a protein content of less than 2 g/100 mL (2 g%). Rivalta test may be used to differentiate an exudate from a transudate. It is not clear if there is a distinction in the difference of transudates and exudates in plants.

Plant exudates

Plant exudates include saps, gums,

latex Latex is an emulsion (stable dispersion) of polymer microparticles in water. Latices are found in nature, but synthetic latices are common as well. In nature, latex is found as a wikt:milky, milky fluid, which is present in 10% of all floweri ...

, and

resin A resin is a solid or highly viscous liquid that can be converted into a polymer. Resins may be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures of organic compounds, predominantly terpenes. Commo ...

. Sometimes

nectar Nectar is a viscous, sugar-rich liquid produced by Plant, plants in glands called nectaries, either within the flowers with which it attracts pollination, pollinating animals, or by extrafloral nectaries, which provide a nutrient source to an ...

is considered an exudate. Plant seeds exudate a variety of molecules into the spermosphere, and roots exudate into the rhizosphere; these exudates include acids, sugars,

polysaccharides Polysaccharides (), or polycarbohydrates, are the most abundant carbohydrates found in food. They are long-chain polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. This carbohydrate can react with wat ...

and

ectoenzyme An exoenzyme, or extracellular enzyme, is an enzyme that is secreted by a cell (biology), cell and functions extracellular, outside that cell. Exoenzymes are produced by both prokaryotic and eukaryotic cells and have been shown to be a crucial co ...

s, and collectively account for 40% of root carbon. Exudation of these compounds has various benefits to the plant and to the

microorganisms A microorganism, or microbe, is an organism of microscopic size, which may exist in its single-celled form or as a colony of cells. The possible existence of unseen microbial life was suspected from antiquity, with an early attestation in ...

of the rhizosphere.

References

External links