Pathology is the study of the nature and causes of diseases, focusing on their origins, mechanisms, and effects on structures and functions. Key aspects include the etiology of diseases, pathogenesis, diagnosis, and the consequences such as sequelae. Additionally, it encompasses various diagnostic tools and branches, including histopathology and genetics, to understand and manage diseases effectively.

1. INTRODUCTION
PATHOLOGY
1. It is the study of nature & cause of disease which
involves changes in structure and function
2. The aspects of a disease process that form the core
of pathology include:
3. its cause, the pathogenesis that is the
sequence of events which give rise to the
manifestations of the disease), and
4. the morphologic changes (structural alterations
induced in cells & tissues by the disease

2. What is Pathology?
 Pathology is the study of patterns, causes,
mechanisms and effects of illness
(disease)
 To interpret symptoms and signs it is
important to know the range of
abnormalities possible in an organ system
 Basis of differential diagnosis

3. Pathology clinical disciplines
 Histopathology
 Haematology
 Clinical chemistry
 Immunology
 Microbiology
 Genetics

4. Pathology - diagnostic tools
 Structural examination
◦ Fluid and tissue cytology
◦ Biopsy
◦ Autopsy

5. Pathology encompasses all
aspects of disease
 Genetic function
 Physiological/ biochemical function
 Structural abnormalities
◦ Cells
◦ Tissues
◦ Organs

6. Aetiology
 The root cause of a disease process
• Genetic
• Environmental agent
• Immune
• Infective
• Neoplastic
• Primary inflammatory
• Vascular
• Iatrogenic

7. Pathogenesis
 The molecular, physiological and cellular
mechanisms that occur after the first
injury and which lead to the expression of
a disease
 Understanding pathogenesis is important
in choosing, or developing, an appropriate
therapy

8. Natural history
 The course of a disease process
◦ Untreated
◦ Modified by therapy
 Prognosis*
◦ Disability
◦ Disease-free survival
◦ Survival
* With its prefix pro-, meaning "before", prognosis means basically "knowledge
beforehand" of how a situation is likely to turn out. Prognosis was originally a strictly
medical term, but it soon broadened to include predictions made by experts of all
kinds. Thus, for example, economists are constantly offering prognoses (notice the
irregular plural form) about where the economy is going, and climate scientists
regularly prognosticate about how quickly the earth's atmosphere is warming.
Diagnosis: the process of determining by examination the nature and
circumstances of a diseased condition i.e. the decision reached from such examination.
Abbreviation: Dx.

9. Sequelae
 The clinical and pathological
consequences of a disease process
(A sequela (UK: /sᵻˈkwiːlə/, US: /sᵻˈkwɛlə/;
usually used in the plural, sequelae) is a
pathological condition resulting from a disease,
injury, therapy, or other trauma. Typically,
a sequela is a chronic condition that is a
complication which follows a more acute
condition)

10. Studying Pathology
 This is a GOOD thing…
 Pathology enters all disciplines of
medicine
 Pathology is the bedrock of good clinical
medicine
◦ General Pathology
◦ Systems Pathology

11. Pathological Manifestations
 Adaptation of cells to environmental
changes
 What happens to cells when they cannot
adapt and how they die
 Disorders due to abnormal cell growth, for
example cancer
 Tissue responses to injury and how
tissues heal

12.  Atheroma* and disease of blood vessels
 Thrombosis and infarction
 Tumour pathology
◦ Classification and nomenclature
◦ Behaviour and diagnosis
◦ Causation and cell biology
 Revision genetics
* Atheroma :degeneration of the walls of the arteries caused by
accumulated fatty deposits and scar tissue, and leading to
restriction of the circulation and a risk of thrombosis.
As well, the fatty material which forms deposits in the arteries.

13.  Systems pathology continues through
the whole of the clinical course
 Pathology tutorial system with guided
reading
 Probably 40% of the content of all
examinations in clinical course consist
of Pathology

14. It is defined as a variety of stresses a cell encounters
as a result of change in its internal and external environment

16. Flow chart (last page) depicts apoptotic and necrotic beta cell death
cascades along with possible modes of intervention. Causes/agents
of beta cell death are indicated in red while agents/strategies for
prevention of beta cell damage are indicated in blue. Red arrows
stand for possible sites of intervention. IL-11: Interleukin 11, IKK:
Inhibitor of kappa kinase, iNOS: inducible nitric oxide synthase,
NO, Nitric oxide, STZ: Streptozotocin, ROS: Reactive oxygen
species, PARP: Poly (ADP-Ribose) Polymerase, CAT: Catalase:
SOD, superoxide dismutase; GSH: glutathione peroxidase, NF-kB:
Nuclear Factor kappa B.
Mechanisms of (islet) cell death.

17. Definition:
If the limits of adaptive
responses are exceeded
or if cells are exposed to
injurious agents or
stress, deprived of
essential nutrients, or
become compromised by
mutations that affect
essential cellular
constituents, a sequence
of events follows that is
termed cell injury.
Cell injury

18. Overview of Cell Injury •
Cells actively control the composition of their
immediate environment and intracellular milieu
within a narrow range of physiological parameters
(“homeostasis ”) • Under physiological stresses or
pathological stimuli (“injury”), cells can undergo
adaptation to achieve a new steady state that would
be compatible with their viability in the new
environment. • If the injury is too severe
(“irreversible injury”), the affected cells die.

19. Causes of Cell Injury
•Hypoxia and ischemia
• Chemical” agents
•“Physical” agents
•Infections
•Immunological reactions
•Genetic defects
•Nutritional defects
•Aging

20. Apoptosis
A natural process of self-
destruction by degradative enzymes in certain cells, such as
epithelial cells and erythrocytes,
that are genetically programmed to have a limited lifespan or
are damaged, as by irradiation or toxic drugs.
Also called programmed cell death.

21. Necrosis
Pathologic death of one or more cells, or of a portion of tissue or
organ, resulting from irreversible damage; earliest irreversible
changes are mitochondrial, consisting of swelling and granular
calcium deposits seen by electron microscopy; most frequent
visible alterations are nuclear: pyknosis, shrunken and abnormally
dark basophilic staining; karyolysis, swollen and abnormally pale
basophilic staining; or karyorrhexis, rupture, and fragmentation of
the nucleus.
After such changes, the outlines of individual cells are indistinct
& affected cells may merge, sometimes forming focus
of coarsely granular, amorphous, or hyaline material.

22. Necrosis – phenomenon continued
( referred as Death of some or all cells in an organ or tissue).
The process involves swelling of the nucleus (pyknosis),
fragmentation
of nucleus (karyorrhexis) and complete dissolution of the
nuclear chromatin (karyolysis). Necrosis is caused by disease,
Trauma* or interference with blood supply.
There are many sequelae to ocular necrosis (e.g. inflammation,
reduction in aqueous humour production following ciliary
epithelium necrosis, corneal opacity following necrosis of
corneal epithelial cells, and visual loss and floaters following
retinal necrosis).
*Trauma is often the result of an overwhelming amount of stress that exceeds
one's ability to cope, or integrate the emotions involved with that experience.

23. Types Of Necrosis
There are six types of Necrosis:
•Coagulative necrosis
•Liquefactive necrosis
•Caseous necrosis
•Fat necrosis
•Fibroid necrosis
•Gangrenous necrosis
The type of necrosis can often be categorized based on how the
cells look after death. Sometimes the entire cell loses its
structure, and sometimes the outer architecture remains the same
and only the inside is affected.

24. More Common Types
Aseptic necrosis necrosis without infection or inflammation.
Caseous necrosis in which the tissue is soft, dry and cheesy, occurring typical
ly in tuberculosis.
Central necrosis affecting the central portion of an affected bone, cell or
lobule of the liver.
cheesy necrosis in which the tissue resembles cottage cheese; most often seen
in tuberculosis.
coagulation necrosisdeath of cells, the protoplasm of the cells becoming fixed
and opaque by coagulation of the protein elements, the
cellular outline persisting for a long time.
colliquative necrosis see liquefactive necrosis (below).
liquefactive necrosis when necrotic material becomes softened and liquefied.
moist necrosis here the dead tissue is wet and soft.
Zenker's necrosis wherein occurs the
hyaline degeneration and necrosis of striated muscle; also called Zenker's
degeneration.

25. Apoptosis & Necrosis
In General, there are two steps that occur when a cell dies:
1. Proteins inside the cell break down
2. The body releases enzymes that digest these dead cells
The apoptosis process is a natural part of the cell's life cycle, and the body is
ready to carry the dead cell materials away. In necrosis, however, the body isn't
prepared to remove the dead cells, and as a result, causes an inflammatory
response.
Cells need blood to live, and any interruption to blood flow results in necrosis.
Injury, infection, disease, toxins, and many other factors can block blood from
getting to a cell and cause unnatural death. Sometimes a dead cell releases
chemicals that can affect the nearby cells, spreading necrosis to wide areas in a
condition called gangrene, which occurs when tissues in certain areas, usually
the hands and feet, die. Again, a dead cell can't turn back into a living one, so
the only cure for gangrene is to amputate the area.
Sub cellular Responses: Autophagy is a common phenomenon involved in the
removal of damaged organelles during cell injury and the cellular remodeling of
differentiation, and it is particularly pronounced in cells undergoing atrophy
induced by nutrient deprivation or hormonal involution.