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Basic Pathology Terms

Posted by medliorator on January 6, 2008

Infection: detrimental colonization of a host organism by a foreign species.
the infecting organism seeks to utilize the host’s resources to multiply (usually at the expense of the host). The infecting organism, or pathogen, interferes with the normal functioning of the host and can lead to chronic wounds, gangrene, loss of an infected limb, and even death.The host’s response to infection is inflammation (read below). Colloquially, a pathogen is usually considered a microscopic organism though the definition is broader, including feces, parasites, fungi, viruses, prions, and viroids. A symbiosis between parasite and host, whereby the relationship is beneficial for the former but detrimental to the latter, is characterised as parasitism.

 

The branch of medicine that focuses on infections and pathogens is infectious disease.

 

Inflammation: complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. It is a protective attempt… to remove the injurious stimuli as well as initiate the healing process. Inflammation is not a synonym for infection… infection is caused by an exogenous pathogen, while inflammation is the response of the organism to the pathogen.

 

In the absence of inflammation, wounds and infections would never heal and progressive destruction of the tissue would compromise the survival of the organism. However, inflammation which runs unchecked can also lead to a host of diseases, such as hay fever, atherosclerosis, and rheumatoid arthritis. It is for this reason that inflammation is normally tightly regulated by the body.

 

Inflammation can be classified as either acute or chronic.

 

Necrosis: accidental death of cells and living tissue. Necrosis is less orderly than apoptosis, which is part of programmed cell death. In contrast to apoptosis, cleanup of cell debris by phagocytes of the immune system is generally more difficult, as the disorderly death generally does not send cell signals which tell nearby phagocytes to engulf the dying cell. This lack of signalling makes it harder for the immune system to locate and recycle dead cells which have died through necrosis than if the cell had undergone apoptosis.

 

The release of intracellular content after cellular membrane damage is the cause of inflammation in necrosis. There are many causes of necrosis including prolonged exposure to injury, infection, cancer, infarction, poisons, and inflammation. Severe damage to one essential system in the cell leads to secondary damage to other systems, a so-called “cascade of effects”. Necrosis can arise from lack of proper care to a wound site.

 

Necrosis is accompanied by the release of special enzymes, that are stored by lysosomes, which are capable of digesting cell components or the entire cell itself. The injuries received by the cell may compromise the lysosome membrane, or may initiate an unorganized chain reaction which causes the release in enzymes.

 

Unlike apoptosis, cells that die by necrosis may release harmful chemicals that damage other cells. In biopsy, necrosis is halted by fixation or freezing.

 

Atrophy: partial or complete wasting away of a part of the body. Causes… include poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply to the target organ, disuse or lack of exercise or disease intrinsic to the tissue itself. Hormonal and nerve inputs that maintain an organ or body part are referred to as trophic.

 

Atrophy is a general physiological process of reabsorption and breakdown of tissues, involving apoptosis on a cellular level. When it occurs as a result of disease or loss of trophic support due to other disease, it is termed pathological atrophy, although it can be a part of normal body development and homeostasis as well.

 

Hypertrophy: increase of the size of an organ or in a select area of the tissue. It should be distinguished from hyperplasia which occurs due to cell division increasing the number of cells while their size stays the same; hypertrophy occurs due to an increase in the size of cells, while the number stays the same.

 

Fibrosis: formation or development of excess fibrous connective tissue in an organ or tissue as a reparative or reactive process, as opposed to a formation of fibrous tissue as a normal constituent of an organ or tissue.

 

Tuberculosis: a common and deadly infectious disease caused by mycobacteria, mainly Mycobacterium tuberculosis. Tuberculosis most commonly attacks the lungs (as pulmonary TB) but can also affect the central nervous system, the lymphatic system, the circulatory system, the genitourinary system, bones, joints and even the skin.

 

Other mycobacteria such as Mycobacterium bovis, Mycobacterium africanum, Mycobacterium canetti, and Mycobacterium microti can also cause tuberculosis, but these species do not usually infect healthy adults.

 

Over one-third of the world’s population has been exposed to the TB bacterium, and new infections occur at a rate of one per second. Not everyone infected develops the full-blown disease; asymptomatic, latent TB infection is most common. However, one in ten latent infections will progress to active TB disease, which, if left untreated, kills more than half of its victims.

 

In 2004, mortality and morbidity statistics included 14.6 million chronic active TB cases, 8.9 million new cases, and 1.6 million deaths, mostly in developing countries. In addition, a rising number of people in the developed world are contracting tuberculosis because their immune systems are compromised by immunosuppressive drugs, substance abuse, or HIV/AIDS. The rise in HIV infections and the neglect of TB control programs have enabled a resurgence of tuberculosis.

 

Sarcoidosis: an immune system disorder characterised by non-caseating granulomas (small inflammatory nodules) that most commonly arises in young adults. The cause of the disease is still unknown. Virtually any organ can be affected; however, granulomas most often appear in the lungs or the lymph nodes.

 

Symptoms can occasionally appear suddenly but usually appear gradually. The clinical course varies and ranges from asymptomatic disease that resolves spontaneously to a debilitating chronic condition that may lead to death.

 

Granuloma: a group of epithelioid macrophages surrounded by a lymphocyte cuff. Granulomas are small nodules… seen in a variety of diseases such as Crohn’s disease, tuberculosis, Leprosy, sarcoidosis, berylliosis and syphilis. It is also a feature of Wegener’s granulomatosis and Churg-Strauss syndrome, two related autoimmune disorders.

 

An important aspect of granulomas is whether they are caseating or not. Caseation (literally: turning to cheese) is a form of necrosis at the centre of a granuloma and is a feature of the granulomas of tuberculosis.

Pathology Terms (part1) [My MD Journey]

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2 Responses to “Basic Pathology Terms”

  1. Y. S. said

    Hopefully I’ll be posting Part2 soon. 😉

  2. I have a granuloma in my left side of my lumg. I ask my doctor and she toll me that is not important that I should’t worry about it but, I’m having a dried cuff and that worries me. I’m not happy with my doctor answer.

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