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PATHOLOGY & PATHOPHYSIOLOGY
CHAPTER 2: CELLULAR PATHOLOGY
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OBJECTIVES
Discuss the factors that can cause injury to cells
Differentiate between the various ways that cells adapt to
stressors
Look at the two ways that cell death can occur
Classify body cells into three categories according to their
ability to undergo regeneration
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CELL STRESSORS
Physical agents, e.g. trauma, electric shock, extreme cold/heat
Chemical agents, e.g. insecticides, alcohol and heavy metals
Biological agents, e.g. viruses, bacteria and worms
Nutritional agents (deficiency, obesity and starvation)
Free radicals
Lack of oxygen
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CELL STRESSORS
NUTRITIONAL AGENTS:
Malnutrition:
Person does not ingest adequate amounts of nutrients for
normal body function
Protein-energy malnutrition: When you break down lean
tissue (fat-free tissue: skeletal muscles, viscera and cells of
the immune system or blood) in order to supply your body
with energy. It occurs in cases of starvation or serious
illnesses, e.g. cancer
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CELL STRESSORS
NUTRITIONAL AGENTS:
Malabsorption:
Inability of the small intestine to absorb
one/more necessary nutrients, e.g.
gastro-intestinal infections, pernicious
anaemia and coeliac disease
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CELL STRESSORS
NUTRITIONAL AGENTS:
Obesity:
Obesity is defined as a condition characterised by excess body fat
Clinically, obesity and overweight have been defined in terms of the BMI
(body mass index)
Overweight is a BMI of ≥ 25 and obesity is BMI of ≥ 30
It is the 2nd leading cause of preventable death in the US
Research suggests that fat distribution may be a more important factor
for morbidity and mortality than overweight or obesity
Two types: central and peripheral obesity
Central obesity is more of a health risk than peripheral obesity
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OBESITY
Obesity increases risk for:
Hypertension
Type 2 diabetes
Coronary heart disease
Gallstones
Hernias
Varicose veins
Osteo-arthritis
Post-operative complications
Infertility
Carpal tunnel syndrome
Sleep apnea
Cancer of endometrium, prostate, colon, uterus, ovaries, kidneys,
gallbladder and breast (in post-menopausal women)
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Weight loss is important as it improves metabolic or
hormonal abnormalities
Prevention:
OBESITY
Regular good quality meals
Increased activity
Education! (parents, children,
teenagers and adults)
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OBESITY
Treatment of Obesity:
Healthy diet:
Must be individualised
500 to 1000 kcal/day less than current dietary intake
A reduction of dietary fat without a calorie deficit will not result in
weight loss
Frequent contact with a dietician/nutritionist
Increased physical therapy:
Reduces body fat
Prevents the loss of muscle mass that often occurs with weight loss
Exercise should be started slowly
Aim for 30 minutes of moderate activity for most days of the week
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OBESITY
Treatment of Obesity:
Behaviour therapy:
Self-monitoring of eating habits
Stress management
Stimulus control
Problem solving
Social support
Relapse control
Pharmacotherapy
Surgery
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CELL STRESSORS
What does a cell do when it is under “stress”?
The cell tries to adapt in order to secure its survival by
undergoing changes in their size, number and type
When a cell experiences prolonged or overwhelming stress it
will become injured or die
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CELLULAR ADAPTION
ATROPHY:
Cells become smaller in size
Why does atrophy occur?
The cell is not getting what it needs OR the cell is not as necessary for the
body anymore
Atrophy of a cell decreases its energy requirements
Occurs when there is:
disuse
denervation
loss of endocrine stimulation
inadequate nutrition
decreased blood flow to a cell
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CELLULAR ADAPTION
HYPERTROPHY:
Increase in cell size
Why does hypertrophy occur?
Occurs when there is an increase in workload on cells that cannot divide
(skeletal muscle, cardiac muscle)
The cell requires more nutrients and oxygen
Examples:
Skeletal muscles that become bigger due to exercise
Increase in the size of cardiac muscle cells if a person has high blood
pressure
One kidney becomes bigger if the other one is removed
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CELLULAR ADAPTION
HYPERTROPHY:
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CELLULAR ADAPTION
METAPLASIA:
Reversible change in which one cell type is replaced by another cell type
Why does metaplasia occur?
Usually occurs in response to chronic irritation and inflammation
Aim is to protect
Examples:
Trachea of smokers
Intestinal
Cervical http://ocw.tufts.edu/Content/51/lecturenotes/551831/552054
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CELLULAR ADAPTION
DYSPLASIA:
Deranged cell growth in a tissue that results in cells that vary in size,
shape and organisation
Why does dysplasia occur?
Examples:
Respiratory tract
Uterine cervix
Associated with chronic irritation
and inflammation
Warning sign of impending cancer
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CELL INJURY
When cell adaptation is not enough to protect the cell…
Mild injury
Repair
Healing
Severe injury
Apoptosis
Necrosis
Cell death
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CELL INJURY
APOPTOSIS:
“Programmed cell death”
Examples:
After 100–120 days red blood cells are destroyed in the spleen by means of
apoptosis
Occurs in the uterus during the menstrual cycle
Occurs in breast tissue once the baby is weaned
A normal process that occurs at the
end of the lifespan of a cell
http://www.systembio.com/rnai-libraries/pathway-focused/apoptosis/overview
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CELL INJURY
NECROSIS:
Abnormal cell death, e.g. during a heart attack, a part of the heart muscle
dies
Differs from apoptosis in that it provokes inflammation around the dead
cells
Examples:
Abscess
Infarction
In the centre of TB granulomas Necrotic leg wound caused by a brown
recluse spider bite http://en.wikipedia.org/wiki/Necrosis
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CELL INJURY
GANGRENE:
This term is used when a considerable
mass of tissue undergoes necrosis
The dead tissue becomes invaded by
anaerobic bacteria
The affected area is brown or black
and smells foul
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TISSUE REPAIR AND HEALING
REGENERATION:
Injured cells are replaced with new cells of same
type or with scar tissue
Depends on the type of cell and amount of
damage
There are 3 types of cells (depending on how they
regenerate):
Labile
Stable
Permanent
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QUESTIONS