Pathology definitions

PATHOLOGY DEFINITIONS

1. PATHOLOGY DEFINITIONS
PATHOLOGY:
Is the study (logos) of disease (pathos, suffering)
HYPERTROPHY:

Hypertrophy is an increase in the size of cells resulting in increase in the
size of the organ.

HYPERPLASIA:

Increased number of cells

ATROPHY:

Shrinkage in the size of the cell by the loss of cell substance is known as
atrophy

METAPLASIA:

Metaplasia is a reversible change in 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 Degradative action 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 lysosomal digestion of the cell’s own components.

FATTY CHANGE (STEATOSIS) :

Fatty change refers to any abnormal accumulation of triglycerides within
parenchymal cells

CELLULAR AGING:

Progressive decline in the life span and functional capacity of cells.

INFLAMMATION:

Inflammation is a protective response involving host cells, 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 brought to 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 from the blood, leukocytes move toward sites of
infection or injury along a chemical gradient

3. REACTIVE OXYGEN SPECIES:

ROS are synthesized via the NADPH oxidase (phagocyte oxidase) pathway
and are released from neutrophils and macrophages that are activated by
microbes, immune complexes, cytokines, and a variety of other inflammatory
Stimuli

COMPLEMENT SYSTEM:

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 those have self-renewal capacity and asymmetric replication property

GROWTH FACTORS:

Growth factors are proteins that stimulate the survival and Proliferation of
particular cells, and may also promote migration, Differentiation, and other
cellular responses

ANGIOGENESIS:

Angiogenesis is the process of new blood vessel development 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 excessive bleeding after blood
vessel damage

HYPEREMIA:

Increase in blood volume within a tissue – active process

CONGESTION:

Increase in blood volume within a tissue – passive process

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 serosal surfaces

PURPURA:

Slightly larger (3 to 5 mm) hemorrhages.

ECCHYMOSES:

Larger (1 to 2 cm) subcutaneous hematomas

5. HEMOSTASIS:

Comprises a series of regulated processes that maintain blood in a fluid,
clot-free state in normal vessels while rapidly forming a localized hemostatic plug
at the site of vascular injury

COAGULATION CASCADE:

Is a successive series of amplifying enzymatic reactions. At each step in the
process, a proenzyme is proteolyzed to become an active enzyme, which in turn
proteolysis the next proenzyme in 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 from its point of origin.

INFARCTION:

An infarct is 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 tissue perfusion and cellular hypoxia

6. IMMUNITY:

Refers to protection against infections, and the immune system is the
collection of cells and molecules that are responsible for defending the body
against the countless pathogenic microbes in the environment


HYPERSENSITIVITY:

Injurious immune reactions are grouped as hypersensitivity.

AUTOIMMUNITY:

Reactions against self-antigens

IMMEDIATE (TYPE I) HYPERSENSITIVITY:

Immediate hypersensitivity is a tissue reaction that occurs rapidly (typically
within minutes) after the interaction of antigen with IgE antibody that is bound to
the surface of mast cells in a sensitized host

(TYPE II HYPERSENSITIVITY) :

Antibody-mediated (type II) hypersensitivity disorders are caused by
antibodies directed against target antigens on the surface of cells or other tissue
components.


(TYPE III HYPERSENSITIVITY) :

Antigen–antibody (immune) complexes that are formed in the circulation
may deposit in blood vessels, leading to complement activation and acute
inflammation.

7. T CELL–MEDIATED (TYPE IV) HYPERSENSITIVITY:

Several autoimmune disorders, as well as pathologic reactions to
environmental chemicals and persistent microbes, are now known to be caused
by T cells.

IMMUNOLOGIC TOLERANCE:

Immunologic tolerance is unresponsiveness to an antigen that is induced by
exposure of 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 produce a
nonsuppurative proliferative synovitis that frequently progresses to destroy
Articular cartilage and underlying bone with resulting disabling arthritis

SJÖGREN SYNDROME:

Sjögren syndrome is a clinicopathologic entity characterized by dry eyes
(keratoconjunctivitis sicca) and dry mouth (xerostomia), resulting from immune-
mediated destruction of the lacrimal and salivary glands.

SYSTEMIC SCLEROSIS (SCLERODERMA) :

Systemic sclerosis (SS) is an immunologic disorder characterized by
excessive fibrosis 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
responsible for tissue damage and functional compromise

8. NEOPLASIA:

Is an abnormal mass of tissue, the growth of which exceeds and it’s
uncoordinated with that of the normal tissues and persist in the same excessive
manner after cessation of the stimuli which evoked the changes.
Modern era: 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 produce adverse health 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 soft lipid 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 apart the laminar planes of the
media to form a blood-filled channel within the aortic wall

VASCULITIS:

Is a general term for vessel wall inflammation.

VARICOSE VEINS:

Abnormally dilated tortuous veins produced by chronically increased
intraluminal pressures and weakened vessel wall support.

ISCHEMIC HEART DISEASE:

Is a broad term encompassing several closely related syndromes caused by
myocardial ischemia— an imbalance between cardiac blood supply (perfusion)
and myocardial oxygen and nutritional requirements

ANEMIA:

Is defined as a reduction in the oxygen-transporting capacity of blood,
which usually stems from a decrease in the red cell mass to subnormal levels


MEAN CELL VOLUME (MCV) :

Average volume per red cell, expressed in femtoliters (cubic microns)

10. MEAN CELL HEMOGLOBIN (MCH):

The average mass of hemoglobin per red cell, expressed in pictograms

MEAN CELL HEMOGLOBIN CONCENTRATION (MCHC):

The average concentration of hemoglobin in a given volume of packed red
cells, expressed in grams per deciliter

RED CELL DISTRIBUTION WIDTH (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 failure and pancytopenia

HODGKIN LYMPHOMA:

Encompasses a distinctive group of neoplasms that are characterized by the
presence of a tumor giant cell, the Reed-Sternberg cell

MYELOID NEOPLASMS:

Arise from hematopoietic progenitors and typically give rise to 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 progressive to fatal if untreated.

11. MYLODYSPLASTIC SYNDROMES:

Are a heterogeneous groups of acquired clonal stem cell disorders
characterized by occurrence in the elderly persons, dysplasia one or more
hematopoietic cell lineage, ineffective erythropoiesis, increased risk of
transformation in to acute myeloid leukemia’s.

MYELOPROLIFERATIVE DISOEDERS:

Are the clonal neoplastic disorders of pluripotent hematopoietic stem cell
characterized by excessive proliferation of one or more of the myeloid cell lines
like granulocytic, erythroid, megakaryocytic.

POLYCYTHEMIA VERA:

Is a myeloproliferative disorder characterized by trilineage hyperplasia in
bone marrow with predominant involvement of erythroid series

PRIMARY MYELOFIBROSIS:

Is a clonal myeloproliferative neoplasm characterized by trilineage
proliferation in bone marrow , reactive bone marrow fibrosis and extra medullary
hematopoiesis.

ESSENTIAL THROMBOCYTHAEMIA:

Is a clonal myeloproliferative disorder 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 lymphoproliferative disorder of B cell origin characterized
by pancytopenia, splenic enlargement & hairy cells in bone marrow and other
sites.

PLASMA CELL DYSCRASIAS:

Also called paraproteinaemias or monoclonal gammopathies 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 throughout the microcirculation. As a consequence,
platelets and coagulation factors are consumed and, secondarily, fibrinolysis is
activated

ACUTE RESPIRATORY DISTRESS SYNDROME:

Acute respiratory distress syndrome (ARDS) is a clinical syndrome caused by
diffuse alveolar capillary and epithelial damage. The usual course is characterized
by rapid onset of life-threatening respiratory insufficiency, cyanosis, and severe
arterial hypoxemia that is refractory to oxygen therapy and may progress to
multisystem organ failure

13. EMPHYSEMA:

Is characterized by abnormal permanent enlargement of the air spaces
distal to the terminal bronchioles, accompanied by destruction of their walls
without significant fibrosis.

CHRONIC BRONCHITIS:

It is defined by the presence of a persistent productive cough for at least 3
consecutive months in at least 2 consecutive years.

ASTHMA:

Asthma is a chronic inflammatory disorder of the airways that causes
recurrent episodes of wheezing, breathlessness, chest tightness, and cough,
particularly at night and/or early in the morning. The hallmarks of the disease are
intermittent and reversible airway obstruction, chronic bronchial inflammation
with eosinophils, bronchial smooth 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 from or associated with
chronic necrotizing infections

SARCOIDOSIS:

Is a multisystem disease of 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.