PATHOLOGY DEFINITIONS

1. PATHOLOGY DEFINITIONS
PATHOLOGY:
Is the study (logos) of disease (pathos, suffering)
HYPERTROPHY:
Hypertrophy is an increase in the sizeof cells resulting in increase in the
sizeof the organ.
HYPERPLASIA:
Increased number of cells
ATROPHY:
Shrinkagein the sizeof the cell by the loss of cell substanceis known as
atrophy
METAPLASIA:
Metaplasia is a reversible changein which one adult cell type (epithelial or
mesenchymal) is replaced by another adult cell type
NECROSIS:
Necrosis is the type of cell death that is associated with loss Of membrane
integrity and leakage of cellular contents culminating In dissolution of cells,
largely resulting from the Degradativeaction of enzymes on lethally injured cells
APOPTOSIS:
Apoptosis is a pathway of cell death in which cells activate Enzymes that
degrade the cells own nuclear DNA and nuclear And cytoplasmic proteins

2. AUTOPHAGY:
Refers to lysosomaldigestion of the cell’s own components.
FATTY CHANGE (STEATOSIS) :
Fatty changerefers to any abnormalaccumulation of triglycerides within
parenchymalcells
CELLULAR AGING:
Progressivedeclinein the life span and functional capacity of cells.
INFLAMMATION:
Inflammation is a protective responseinvolving hostcells, blood vessels,
and proteins and other mediators that is intended to eliminate the initial cause of
Cell injury, as well as the necrotic cells and tissues resulting from the original
insult, and to initiate the process of repair.
LEUKOCYTE RECRUITMENT:
Leukocytes normally flow rapidly in the blood, and in inflammation, they
have to be stopped and broughtto the offending agent or the site of tissue
damage, which are typically outside the Vessels
MARGINATION:
Process of leukocyte accumulation at the periphery of vessels
CHEMOTAXIS:
After extravasating fromthe blood, leukocytes movetoward sites of
infection or injury along a chemical gradient

3. REACTIVEOXYGEN SPECIES:
ROS are synthesized via the NADPH oxidase (phagocyte oxidase) pathway
and are released fromneutrophils and macrophages that are activated by
microbes, immune complexes, cytokines, and a variety of other inflammatory
Stimuli
COMPLEMENTSYSTEM:
Consists of plasma proteins that play an important role in host defense
(immunity) and inflammation
GRANULOMA:
Characterized by aggregates of activated macrophages with scattered
lymphocytes
STEM CELLS:
Defined as thosehave self-renewalcapacity and asymmetric replication property
GROWTH FACTORS:
Growth factors areproteins that stimulate the survivaland Proliferation of
particular cells, and may also promote migration, Differentiation, and other
cellular responses
ANGIOGENESIS:
Angiogenesis is the process of new blood vesseldevelopment from existing
vessels, primarily venules

4. FIBROSIS:
To denote the excessive deposition of collagen and other ECM components
in a tissue
HEMOSTASIS:
Is the process of blood clotting that prevents excessivebleeding after blood
vesseldamage
HYPEREMIA:
Increasein blood volume within a tissue – active process
CONGESTION:
Increasein blood volume within a tissue – passiveprocess
HEMORRHAGE:
Defined as the extravasation of blood from vessels, occurs in a variety of
settings
PETECHIAE:
Minute (1 to 2 mm in diameter) hemorrhages into skin, mucous
membranes, or serosalsurfaces
PURPURA:
Slightly larger (3 to 5 mm) hemorrhages.
ECCHYMOSES:
Larger (1 to 2 cm) subcutaneous hematomas

5. HEMOSTASIS:
Comprises a series of regulated processes thatmaintain blood in a fluid,
clot-free state in normalvessels while rapidly forming a localized hemostatic plug
at the site of vascular injury
COAGULATIONCASCADE:
Is a successiveseries of amplifying enzymatic reactions. At each step in the
process, a proenzymeis proteolyzed to become an active enzyme, which in turn
proteolysis the next proenzymein the series, eventually leading to the activation
of thrombin and the formation of fibrin
THROMBOSIS ((CALLED VIRCHOW’S TRIAD):
(1) Endothelial injury, (2) Stasis or turbulent blood flow, and
(3) Hypercoagulability of the blood
EMBOLISM:
An embolus is an intravascular solid, liquid, or gaseous mass that is carried
by the blood to a site distant fromits point of origin.
INFARCTION:
An infarctis an area of ischemic necrosis caused by occlusion of the
vascular supply to the affected tissue
SHOCK:
Is characterized by systemic hypo perfusion of tissues; it can be caused by
diminished cardiac output or by reduced effective circulating blood volume. The
Consequences are impaired tissueperfusion and cellular hypoxia

6. IMMUNITY:
Refers to protection againstinfections, and the immune systemis the
collection of cells and molecules that are responsiblefor defending the body
against the countless pathogenic microbes in the environment
HYPERSENSITIVITY:
Injurious immunereactions are grouped as hypersensitivity.
AUTOIMMUNITY:
Reactions against self-antigens
IMMEDIATE(TYPEI) HYPERSENSITIVITY:
Immediate hypersensitivity is a tissuereaction that occurs rapidly (typically
within minutes) after the interaction of antigen with IgEantibody that is bound to
the surfaceof mast cells in a sensitized host
(TYPE II HYPERSENSITIVITY) :
Antibody-mediated (typeII) hypersensitivity disorders are caused by
antibodies directed against target antigens on the surfaceof cells or other tissue
components.
(TYPE III HYPERSENSITIVITY) :
Antigen–antibody (immune) complexes that are formed in the circulation
may depositin blood vessels, leading to complement activation and acute
inflammation.

7. T CELL–MEDIATED (TYPE IV) HYPERSENSITIVITY:
Several autoimmune disorders, as wellas pathologic reactions to
environmental chemicals and persistent microbes, arenow known to be caused
by T cells.
IMMUNOLOGIC TOLERANCE:
Immunologic tolerance is unresponsiveness to an antigen that is induced by
exposureof specific lymphocytes to that antigen
RHEUMATOID ARTHRITIS:
Rheumatoid arthritis (RA) is a systemic, chronic inflammatory disease
affecting many tissues but principally attacking the joints to producea
nonsuppurativeproliferative synovitis thatfrequently progresses to destroy
Articular cartilage and underlying bone with resulting disabling arthritis
SJÖGRENSYNDROME:
Sjögren syndromeis a clinicopathologic entity characterized by dry eyes
(keratoconjunctivitis sicca) and dry mouth (xerostomia), resulting fromimmune-
mediated destruction of the lacrimal and salivary glands.
SYSTEMIC SCLEROSIS (SCLERODERMA) :
Systemic sclerosis (SS) is an immunologic disorder characterized by
excessivefibrosis in multiple tissues, obliterative vascular disease, and evidence
of autoimmunity, mainly the production of multiple autoantibodies
AMYLOIDOSIS:
Amyloidosis is a condition associated with a number of inherited and
inflammatory disorders in which extracellular deposits of fibrillar proteins are
responsiblefor tissue damageand functional compromise

8. NEOPLASIA:
Is an abnormal mass of tissue, the growth of which exceeds and it’s
uncoordinated with that of the normaltissues and persistin the same excessive
manner after cessation of the stimuli which evoked the changes.
Modernera: Disorder of cell growth that is triggered by a series of acquired
mutations affecting a single cell and its clonal progeny
ANAPLASIA:
Refers to a lack of differentiation in neoplastic cells.
METASTASIS:
Metastases are secondary implants of a tumor that are discontinuous with
the primary tumor and located in remote tissues
FETAL HYDROPS:
Refers to the accumulation of edema fluid in the fetus during intrauterine
growth
OBESITY:
Defined as a state of increased body weight, due to adipose tissue
accumulation, that is of sufficient magnitude to produceadversehealth effects
ATHEROSCLEROSIS:
Is characterized by the presence of intimal lesions called atheroma’s (or
atheromatous or atherosclerotic plaques). Atheromatous plaques are raised
lesions composed of softlipid cores (mainly cholesterol and cholesterol esters,
with necrotic debris) covered by fibrous caps

9. ANEURYSMS:
Congenital or acquired dilations of blood vessels or the heart
AORTIC DISSECTION:
Aortic dissection occurs when blood splays apartthe laminar planes of the
media to forma blood-filled channel within the aortic wall
VASCULITIS:
Is a general term for vesselwall inflammation.
VARICOSE VEINS:
Abnormally dilated tortuous veins produced by chronically increased
intraluminal pressures and weakened vesselwall support.
ISCHEMIC HEARTDISEASE:
Is a broad term encompassing several closely related syndromes caused by
myocardialischemia— an imbalance between cardiac blood supply (perfusion)
and myocardialoxygen and nutritional requirements
ANEMIA:
Is defined as a reduction in the oxygen-transporting capacity of blood,
which usually stems froma decrease in the red cell mass to subnormal levels
MEANCELL VOLUME (MCV) :
Average volumeper red cell, expressed in femtoliters (cubic microns)

10. MEANCELL HEMOGLOBIN(MCH):
The average mass of hemoglobin per red cell, expressed in pictograms
MEANCELL HEMOGLOBINCONCENTRATION (MCHC):
The average concentration of hemoglobin in a given volumeof packed red
cells, expressed in grams per deciliter
RED CELL DISTRIBUTIONWIDTH (RDW):
The coefficient of variation of red cell volume
APLASTIC ANEMIA:
Is a disorder in which multipotent myeloid stem cells are suppressed,
leading to bone marrow failureand pancytopenia
HODGKIN LYMPHOMA:
Encompasses a distinctive group of neoplasms that are characterized by the
presenceof a tumor giant cell, the Reed-Sternberg cell
MYELOID NEOPLASMS:
Arisefrom hematopoietic progenitors and typically give riseto clonal
proliferations that replace normal bone marrow cells
LEUKEMIAS:
With involvement of the bone marrow and the peripheral blood
ACUTE LEUKEMIAS:
Are malignant clonal disorders originating in hematopoietic stem cells
characterized by the proliferation of poorly differentiated blast (immature cells) in
the bone marrow & rapidly progressiveto fatal if untreated.

11. MYLODYSPLASTIC SYNDROMES:
Are a heterogeneous groups of acquired clonal stem cell disorders
characterized by occurrencein the elderly persons, dysplasia oneor more
hematopoietic cell lineage, ineffective erythropoiesis, increased risk of
transformation in to acute myeloid leukemia’s.
MYELOPROLIFERATIVEDISOEDERS:
Are the clonal neoplastic disorders of pluripotent hematopoietic stem cell
characterized by excessiveproliferation of one or more of the myeloid cell lines
like granulocytic, erythroid, megakaryocytic.
POLYCYTHEMIA VERA:
Is a myeloproliferativedisorder characterized by trilineage hyperplasia in
bone marrow with predominant involvement of erythroid series
PRIMARY MYELOFIBROSIS:
Is a clonal myeloproliferativeneoplasm characterized by trilineage
proliferation in bone marrow , reactive bone marrow fibrosis and extra medullary
hematopoiesis.
ESSENTIAL THROMBOCYTHAEMIA:
Is a clonal myeloproliferativedisorder characterized by marked
proliferation of megakaryocytes in bone marrow causing thrombocytosis in the
peripheral blood.
CHRONIC LYMPHOCYTIC LEUKAEMIA:
CLL is a neoplastic disorder characterized by monoclonal proliferation of
immunologically incompetent slowly dividing mature B lymphocyte.

12. HAIRY CELL LEUKEMIA:
Is a rare chronic lymphoproliferativedisorder of B cell origin characterized
by pancytopenia, splenic enlargement & hairy cells in bone marrow and other
sites.
PLASMA CELL DYSCRASIAS:
Also called paraproteinaemias or monoclonalgammopathies are a group of
disorders characterized by neoplastic proliferation of plasma cells & increased
production of a single homogeneous immunoglobulin
LYMPHOMAS:
Are a heterogeneous group of malignant neoplasms which originate
primarily in lymph node or other lymphoid tissues.
INFECTOIUS MONONUCLEOSIS:
Is an acute infectious disease caused by EBV characterized by fever,
pharyngitis, lymphadenopathy, atypical lymphocytosis
DIC:
Is caused by the systemic activation of coagulation and results in the
formation of thrombi throughoutthe microcirculation. As a consequence,
platelets and coagulation factors areconsumed and, secondarily, fibrinolysis is
activated
ACUTE RESPIRATORY DISTRESS SYNDROME:
Acute respiratory distress syndrome(ARDS) is a clinical syndromecaused by
diffusealveolar capillary and epithelial damage. The usual courseis characterized
by rapid onset of life-threatening respiratory insufficiency, cyanosis, and severe
arterial hypoxemia that is refractory to oxygen therapy and may progress to
multisystemorgan failure

13. EMPHYSEMA:
Is characterized by abnormalpermanent enlargement of the air spaces
distal to the terminal bronchioles, accompanied by destruction of their walls
without significantfibrosis.
CHRONIC BRONCHITIS:
Itis defined by the presence of a persistentproductivecough for at least 3
consecutivemonths in at least 2 consecutive years.
ASTHMA:
Asthma is a chronic inflammatory disorder of the airways thatcauses
recurrentepisodes of wheezing, breathlessness, chesttightness, and cough,
particularly at night and/or early in the morning. The hallmarks of the disease are
intermittent and reversibleairway obstruction, chronic bronchial inflammation
with eosinophils, bronchialsmooth muscle cell hypertrophy and hyper reactivity,
and increased mucus secretion
BRONCHIECTASIS:
Is the permanent dilation of bronchi and bronchioles caused by destruction
of the muscle and the supporting elastic tissue, resulting fromor associated with
chronic necrotizing infections
SARCOIDOSIS:
Is a multisystem diseaseof unknown etiology characterized by
noncaseating granulomas in many tissues and organs
NEPHRITIC SYNDROME:
Is a clinical complex, usually of acute onset, characterized by (1) Hematuria
with dysmorphic red cells and red cell casts in the urine; (2) Some degree of
oliguria and azotemia; and (3) Hypertension

14. THROMBOTIC MICROANGIOPATHY:
Refers to lesions seen in various clinical syndromes characterized
morphologically by widespread thrombosis in the microcirculation and clinically
by microangiopathic hemolytic anemia, thrombocytopenia, and, in certain
instances, renal failure
LEUKOPLAKIA:
A White patch or plaque that cannot be scraped off and cannot be
characterized clinically or pathologically as any other disease.