Cellular adaptations, injury and death.. Lecture 1

Chapter I: Cellular responses to stress and
toxic insults: Adaptation, Injury and Death
GENERAL PATHOLOGY
CHAPTER I
CELLULAR RESPONSES TO
STRESS AND TOXIC INSULTS
ADAPTATION, INJURY AND
DEATH

Email: pathologybasics@gmail.com, Website: www.pathologybasics.wix.com/notes
Introduction to this lecture series
 Welcome to series of lectures through ppts
on General pathology
 I, Dr. Ashish Jawarkar am a practising
pathologist based in India.
 The very idea behind this came from my
own experience, the difficulty I faced in
understanding general pathology concepts.
Chapter I: cellular responses to stress and
2

Introduction to this lecture series
 The first seven chapters of Robbins have
immense weightage not just for exams, but
for understanding pathology as a whole.
 I will try here to be brief and precise yet
cover all important aspects with full use of
pictures and multimedia links.
 I hope this will help students in becoming
thorough with pathology concepts.
3

OVERVIEW
 1. Homeostasis and other definitions
 2. Adaptations of cellular growth and
differentiation
 3. Cell injury and cell death
 4. Apoptosis
 5. Intracellular accumulations
 6. Pathologic calcification
 7. Cellular aging
4

Definitions
 1. Homeostasis
 2. Adaptations
 3. Cell injury
 4. Cell death
 5. Intracellular accumulations
 6. Cellular aging
5

Definitions
 Homeostasis
– A normal cell achieves a steady state of
functioning due to its
• Differentiation (genetic)
• State of metabolism
• Effects of neighbouring cells
• Metabolic substrates
– This is called normal homeostasis
6

 That was for the definition
 Robbins tries to explain, but still do we get
it? No?
 After every definition I will try to explain
the concept in an easier way
 So lets understand homeostasis through a
few pictures
7

nd
8

a
9

 For further understanding see the following
youtube video
 https://www.youtube.com/watch?v=XZxu
Qo3ylII
10

 Hope that clears your mind..
 Homeostasis done.. Lets move on..
11

What happens when a cell in
homeostasis is subjected to stress or
injury
12

Definitions
 Adaptation
– When a cell in homeostasis is subjected to
stress, there is a functional and a structural
response from the cell
– It consists of hypertrophy, hyperplasia,
atrophy or metaplasia
– Due to this it achieves a new steady state
– It is a reversible response (see above chart)
13

14

Definitions
 Cell injury
– When cells are exposed to stress/injury and
limits of adaptation are exceeded, a sequence
of events follows termed cell injury
– It is reversible up to a certain point, then
becomes irreversible (cell death)
– Irreversible injury is in form of necrosis or
apoptosis
15

16

Definitions
 Intracellular accumulations
– Some types of stresses which are chronic and
sublethal in nature may lead to certain changes
in cells apart from adaptations, necrosis or
apoptosis
– It may lead to accumulation of a number of
different substances including proteins, lipids
or carbohydrates
17

18

Definitions
 Pathologic calcification
– Calcium is often deposited at sites of cell
death
19

20

Definitions
 Cellular aging
– There is a progressive decline in cellular
function and viability caused by genetic
abnormalities and accumulation of cellular and
molecular damage due to effects of exposure
to exogenous influences
21

22

 That was an overview of what is in store
for us in this chapter…
 Now lets look at each topic one by one..in
detail…
 I will try to be as explanatory as possible
 For any queries you can get back to me at
pathologybasics@gmail.com
23

ADAPTATIONS
24

Hypertrophy
 Definition
 Examples
 Molecular Mechanisms
25

Hypertrophy
 Definition
– Increase in size of the cells
– due to increased synthesis of structural
components
– Happens when non dividing cells such as
myocardium and skeletal muscle cells are
exposed to stress
26

Hypertrophy
 Examples
– Pathological hypertrophy
• Myocardium in hypertension
• Skeletal muscle in response to exercise
– Physiological hypertrophy
• Growth of uterus during pregnancy
27

28

29

30

Pathological Hypertrophy
Mechanism
31

32

33

Physiological Hypertrophy
Mechanism
 Due to cell growth in response to estrogen
34

Hypertrophy
Molecular mechanism
35

Hyperplasia
 Definition
 Examples
 Molecular Mechanisms
36

Hyperplasia
Definition
 Increase in number of cells in the organ
37

Hyperplasia
Examples
 Physiologic hyperplasia
– Hormonal
• Glandular epithelium of the breast during puberty and
pregnancy
– Compensatory
• Liver regeneration
 Pathologic hyperplasia
– Hyperplasia of endometrium due to excess estrogen
– Benign prostatic hypertrophy
– Skin warts (papilloma virus)
38

Hyperplasia
Examples
39

Hyperplasia
Molecular mechnism
40

Atrophy
 Definition
 Examples
 Molecular mechanism
41

Atrophy
Definition
 Atrophy is decrease in size of the organ
due to decrease in cell size and number
42

Atrophy
Examples
 Physiologic atrophy
– Fetal organs – like notochord and thyroglossal duct
– Uterus after parturition
 Pathologic atrophy
– Disuse atrophy after immobilization in fracture cast
– Denervation atrophy
– Ischemic atrophy
– Senile atrophy – heart
– Inadequate nutrition – marasmus, cachexia
– Loss of endocrine stimulation – vaginal, endometrial and
breast atrophy after menopause
– Pressure atrophy – in areas surrounding the tumor
43

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45

46

Atrophy
Molecular mechanism
47

Metaplasia
 Definition
 Examples
 Molecular mechanism
48

Metaplasia
Definition
 It is a reversible change occuring in a
differentiated cell
 One cell type is replaced by another cell
type due to stress/injurious stimuli
 It is always pathological
 If it becomes irreversible, it is called
dysplasia – leads to cancer
49

Metaplasia
Examples
50

51

 That’s all for this lecture…we shall
continue with remaining part of this
chapter in the next lecture
 Keep visiting
facebook.com/pathologybasics for
updates..
Chapter I: Cellular responses to stress and
52

Cellular adaptations, injury and death.. Lecture 1

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