Necrosis - AbsoluteAstronomy.com

Necrosis is the premature death

Death

Death is the permanent termination of the biological functions that sustain a living organism. Phenomena which commonly bring about death include old age, predation, malnutrition, disease, and accidents or trauma resulting in terminal injury....

of cell

Cell (biology)

The cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of life that is classified as a living thing, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos....

s in living tissue

Biological tissue

Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

. Necrosis is caused by factors external to the cell or tissue, such as infection, toxins, or trauma. This is in contrast to apoptosis

Apoptosis

Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, cell shrinkage, nuclear fragmentation, chromatin condensation, and chromosomal DNA fragmentation...

, which is a naturally occurring cause of cellular death. While apoptosis often provides beneficial effects to the organism, necrosis is almost always detrimental and can be fatal.

Cells that die due to necrosis do not usually send the same chemical signals

Signal transduction

Signal transduction occurs when an extracellular signaling molecule activates a cell surface receptor. In turn, this receptor alters intracellular molecules creating a response...

to the immune system that cells undergoing apoptosis do. This prevents nearby phagocyte

Phagocyte

Phagocytes are the white blood cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells. Their name comes from the Greek phagein, "to eat" or "devour", and "-cyte", the suffix in biology denoting "cell", from the Greek kutos, "hollow vessel". They are...

s from locating and engulfing the dead cells, leading to a build-up of dead tissue and cell debris at or near the site of the cell death. For this reason, it is often necessary to remove necrotic tissue surgically

Surgery

Surgery is an ancient medical specialty that uses operative manual and instrumental techniques on a patient to investigate and/or treat a pathological condition such as disease or injury, or to help improve bodily function or appearance.An act of performing surgery may be called a surgical...

, a process known as debridement

Debridement

Debridement is the medical removal of a patient's dead, damaged, or infected tissue to improve the healing potential of the remaining healthy tissue...

Classification

There are seven distinctive morphologic

Morphology (biology)

In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....

patterns of necrosis:

Coagulative necrosis
Coagulative necrosis
Coagulative necrosis is a type of accidental cell death typically caused by ischemia or infarction.It is characterised by the 'ghostly' appearance of cells under light microscopy in the affected area of tissue. In coagulative necrosis the architecture of dead tissue is preserved for at least a...

is typically seen in hypoxic
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...

(low-oxygen) environments, such as an infarction. Cell outlines remain after cell death and can be observed by light microscopy
Microscopy
Microscopy is the technical field of using microscopes to view samples and objects that cannot be seen with the unaided eye...

. Hypoxic
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...

infarcts in the brain however result in Liquefactive necrosis.
Liquefactive necrosis
Liquefactive necrosis
Liquefactive necrosis is a type of necrosis which results in a transformation of the tissue into a liquid viscous mass. Often it is associated with focal bacterial or fungal infections...

(or colliquative necrosis) is usually associated with cellular destruction and pus
Pus
Pus is a viscous exudate, typically whitish-yellow, yellow, or yellow-brown, formed at the site of inflammatory during infection. An accumulation of pus in an enclosed tissue space is known as an abscess, whereas a visible collection of pus within or beneath the epidermis is known as a pustule or...

formation (e.g., pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...

). This is typical of bacterial or, sometimes, fungal infections because of their ability to stimulate an inflammatory reaction. Ischemia
Ischemia
In medicine, ischemia is a restriction in blood supply, generally due to factors in the blood vessels, with resultant damage or dysfunction of tissue. It may also be spelled ischaemia or ischæmia...

(restriction of blood supply) in the brain produces liquefactive, rather than coagulative necrosis due to the lack of any substantial supportive stroma
Stroma (animal tissue)
In animal tissue, stroma refers to the connective, supportive framework of a biological cell, tissue, or organ.The stroma in animal tissue is contrasted with the parenchyma.Examples include:* Stroma of iris...

.
Gummatous necrosis is restricted to necrosis involving spirochaetal infections (e.g., syphilis
Syphilis
Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...

).
Haemorrhagic necrosis is due to blockage of the venous drainage of an organ or tissue (e.g., in testicular torsion
Testicular torsion
Testicular torsion is when the spermatic cord to a testicle twists, cutting off the blood supply. The most common symptom is acute testicular pain and the most common underlying cause is a congenital malformation known as a "bell-clapper deformity". The diagnosis is often made clinically but if it...

).
Caseous necrosis
Caseous necrosis
Caseous necrosis is a form of cell death in which the tissue maintains a cheese-like appearance. The dead tissue appears as a soft and white proteinaceous dead cell mass.-Causes:...

is a specific form of coagulation necrosis typically caused by mycobacteria (e.g., tuberculosis
Tuberculosis
Tuberculosis, MTB, or TB is a common, and in many cases lethal, infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis. Tuberculosis usually attacks the lungs but can also affect other parts of the body...

), fungi, and some foreign substances. It can be considered a combination of coagulative and liquefactive necrosis.
Fatty necrosis
Fat necrosis
Fat necrosis is a form of necrosis characterized by the action upon fat by digestive enzymes.In fat necrosis the enzyme lipase releases fatty acids from triglycerides. The fatty acids then complex with calcium to form soaps...

results from the action of lipase
Lipase
A lipase is an enzyme that catalyzes the formation or cleavage of fats . Lipases are a subclass of the esterases.Lipases perform essential roles in the digestion, transport and processing of dietary lipids in most, if not all, living organisms...

s on fatty tissues (e.g., acute pancreatitis
Acute pancreatitis
Acute pancreatitis or acute pancreatic necrosis is a sudden inflammation of the pancreas. It can have severe complications and high mortality despite treatment...

, breast
Breast
The breast is the upper ventral region of the torso of a primate, in left and right sides, which in a female contains the mammary gland that secretes milk used to feed infants.Both men and women develop breasts from the same embryological tissues...

tissue necrosis).
Fibrinoid necrosis
Fibrinoid necrosis
Fibrinoid necrosis is a form of necrosis, or tissue death, in which there is accumulation of amorphous, basic, proteinaceous material in the tissue matrix with a staining pattern reminiscent of fibrin. It is associated with conditions such as immune vasculitis Fibrinoid necrosis is a form of...

is caused by immune-mediated vascular
Blood vessel
The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...

damage. It is marked by deposition of fibrin
Fibrin
Fibrin is a fibrous, non-globular protein involved in the clotting of blood. It is a fibrillar protein that is polymerised to form a "mesh" that forms a hemostatic plug or clot over a wound site....

-like protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

aceous material in arterial
Artery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....

walls, which appears smudgy and eosinophilic
Eosinophilic
Eosinophilic refers to the staining of certain tissues, cells, or organelles after they have been washed with eosin, a dye.Eosin is an acidic dye; thus, the structure being stained is basic....

on light microscopy.

Arachnogenic necrosis

In the United States, only spider bite

Spider bite

A spider bite is an injury resulting from the bites of spiders or other closely related arachnids.Spiders are active hunters and rely heavily on their bites to paralyze and kill their prey before consuming it. They also bite in self defense...

s from the brown recluse spider

Brown recluse spider

The brown recluse spider or violin spider, Loxosceles reclusa, is a member of the family Sicariidae . The spider has a venomous bite....

(genus Loxosceles) have been proven to cause necrosis. Other spiders of the same genus, such as the Chilean recluse

Chilean recluse

The Chilean recluse spider is a venomous spider, Loxosceles laeta, of the family Sicariidae . In Spanish, it is known as , or "corner spider"; in Portuguese, as or "brown spider"...

in South America, have similarly been shown to cause necrosis in other countries. While both the yellow sac spider

Cheiracanthium

Cheiracanthium is a genus of spiders in the Miturgidae family. Certain species are commonly known as the "yellow sac spider".- Description :...

s and Hobo spider

Hobo spider

The hobo spider is a member of the genus of spiders known colloquially as funnel web spiders, but not to be confused with the Australian funnel-web spider. It is one of a small number of spiders in North America whose bites are generally considered to be medically significant...

are often claimed to possess necrotic venom, these claims have been challenged.

A few other spiders commonly suspected (but not all conclusively proven) of having necrotic venom include:

Hobo spider
Hobo spider
The hobo spider is a member of the genus of spiders known colloquially as funnel web spiders, but not to be confused with the Australian funnel-web spider. It is one of a small number of spiders in North America whose bites are generally considered to be medically significant...

in Northwestern United States
Northwestern United States
The Northwestern United States comprise the northwestern states up to the western Great Plains regions of the United States, and consistently include the states of Oregon, Washington, Idaho, Montana, Wyoming, to which part of southeast Alaska is also sometimes included...

Recluse spider
Recluse spider
The recluse spiders or brown spiders , also known as fiddle-back, violin spiders or reapers, are a venomous genus of spiders known for their necrotic bite, which sometimes produces a characteristic set of symptoms known as Loxoscelism...

Causes

Cellular necrosis can be induced by a number of external sources, including injury

Injury

-By cause:*Traumatic injury, a body wound or shock produced by sudden physical injury, as from violence or accident*Other injuries from external physical causes, such as radiation injury, burn injury or frostbite*Injury from infection...

, infection

Infection

An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...

, cancer

Cancer

Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...

, infarction

Infarction

In medicine, infarction refers to tissue death that is caused by a local lack of oxygen due to obstruction of the tissue's blood supply. The resulting lesion is referred to as an infarct.-Causes:...

, poisons, ROS (Reactive Oxygen Species), and inflammation

Inflammation

Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...

. For example, an infarction (blockage of blood flow to muscular tissue) causes necrosis of muscle tissue due to lack of oxygen to the affected cell, such as occurs in a myocardial infarction

Myocardial infarction

Myocardial infarction or acute myocardial infarction , commonly known as a heart attack, results from the interruption of blood supply to a part of the heart, causing heart cells to die...

-- a heart attack. Certain spider (brown recluse) and snake (rattlesnake

Rattlesnake

Rattlesnakes are a group of venomous snakes of the genera Crotalus and Sistrurus of the subfamily Crotalinae . There are 32 known species of rattlesnake, with between 65-70 subspecies, all native to the Americas, ranging from southern Alberta and southern British Columbia in Canada to Central...

, Bothrops

Bothrops

Bothrops is a genus of venomous pitvipers found in Central and South America. The generic name is derived from the Greek words bothros and ops that mean "pit" and "eye" or "face"; an allusion to the heat-sensitive loreal pit organs. Members of this genus are responsible for more human deaths in the...

) venom

Venom

Venom is the general term referring to any variety of toxins used by certain types of animals that inject it into their victims by the means of a bite or a sting...

s can cause necrosis of the tissue near the bite wound, as can a Group A streptococcus infection (one of the "flesh-eating" bacteria

Necrotizing fasciitis

Necrotizing fasciitis , commonly known as flesh-eating disease or Flesh-eating bacteria syndrome, is a rare infection of the deeper layers of skin and subcutaneous tissues, easily spreading across the fascial plane within the subcutaneous tissue.Necrotizing fasciitis is a quickly progressing and...

).

Necrotic tissue does not undergo the same chemical reactions that normally dying apoptotic tissue does. The sudden failure of one part of the cell triggers a cascade of events. In addition to the lack of chemical signals to the immune system, cells undergoing necrosis can release harmful chemicals into the surrounding tissue. In particular, cells contain small organelles called lysosome

Lysosome

thumb|350px|Schematic of typical animal cell, showing subcellular components. [[Organelle]]s: [[nucleoli]] [[cell nucleus|nucleus]] [[ribosomes]] [[vesicle |vesicle]] rough [[endoplasmic reticulum]]...

s, which are capable of digesting cellular material. Damage to the lysosome

Lysosome

membrane can trigger release of the contained enzymes, destroying other parts of the cell. Worse, when these enzymes are released from the non-dead cell, they can trigger a chain reaction of further cell death. If a sufficient amount of contiguous tissue necrotizes, it is termed gangrene

Gangrene

Gangrene is a serious and potentially life-threatening condition that arises when a considerable mass of body tissue dies . This may occur after an injury or infection, or in people suffering from any chronic health problem affecting blood circulation. The primary cause of gangrene is reduced blood...

. Proper care and treatment of wounds or animal bites plays a key role in preventing this type of widespread necrosis. During a surgical biopsy

Biopsy

A biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...

, this necrosis chain-reaction is halted by fixation

Fixation (histology)

In the fields of histology, pathology, and cell biology, fixation is a chemical process by which biological tissues are preserved from decay, thereby preventing autolysis or putrefaction...

or freezing.

Necrosis typically begins with cell swelling, chromatin

Chromatin

Chromatin is the combination of DNA and proteins that make up the contents of the nucleus of a cell. The primary functions of chromatin are; to package DNA into a smaller volume to fit in the cell, to strengthen the DNA to allow mitosis and meiosis and prevent DNA damage, and to control gene...

digestion, and disruption of the plasma membrane and organelle

Organelle

In cell biology, an organelle is a specialized subunit within a cell that has a specific function, and is usually separately enclosed within its own lipid bilayer....

membranes. Late necrosis is characterized by extensive DNA

DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

hydrolysis

Hydrolysis

Hydrolysis is a chemical reaction during which molecules of water are split into hydrogen cations and hydroxide anions in the process of a chemical mechanism. It is the type of reaction that is used to break down certain polymers, especially those made by condensation polymerization...

, vacuolation of the endoplasmic reticulum

Endoplasmic reticulum

The endoplasmic reticulum is an organelle of cells in eukaryotic organisms that forms an interconnected network of tubules, vesicles, and cisternae...

, organelle breakdown, and cell lysis

Lysis

Lysis refers to the breaking down of a cell, often by viral, enzymic, or osmotic mechanisms that compromise its integrity. A fluid containing the contents of lysed cells is called a "lysate"....

. The release of intracellular content after plasma membrane rupture is the cause of inflammation

Inflammation

in necrosis.

Treatment

Treatment of necrosis typically involves two distinct processes. Usually, the underlying cause of the necrosis must be treated before the dead tissue itself can be dealt with. For example, a snake or spider bite victim will receive anti-venom to halt the spread of the toxins, while an infected patient will receive antibiotics.

Even after the initial cause of the necrosis has been halted, the necrotic tissue will remain in the body. The body's immune response to apoptosis, the automatic breaking down and recycling of the cell material, is not triggered by necrotic cell death.

The standard therapy of necrosis (wounds, bedsores, burns, etc.) is surgical removal

Debridement

Debridement is the medical removal of a patient's dead, damaged, or infected tissue to improve the healing potential of the remaining healthy tissue...

of necrotic tissue. Depending on the severity of the necrosis, this may range from removal of small patches of skin, to complete amputation of affected limbs or organs. Chemical removal, via an enzymatic debriding agent, is another option. In select cases, special maggot therapy

Maggot therapy

Maggot therapy is a type of biotherapy involving the intentional introduction of live, disinfected maggots into the non-healing skin and soft tissue wound of a human or animal for the purpose of cleaning out the...

has been utilized with good results.

In plants

If calcium is deficient, pectin

Pectin

Pectin is a structural heteropolysaccharide contained in the primary cell walls of terrestrial plants. It was first isolated and described in 1825 by Henri Braconnot...

cannot be synthesized, and therefore the cell walls cannot be bonded and thus an impediment of the meristems. This will lead to necrosis of stem and root tips and leaf edges.

External links

Life In The Fast Lane: toxicology Conundrum #018