Chapter - 5
Cellular adaptations
Introduction:
For the sake of survival, cells need to be adjusted in unfavourable
conditions, to release stress, so this process of reversible change in
number, size, phenotype, or function allows the cell to adapt to that
external stress.
If the stress is removed, the cell returns to its normal conditions. But
if injury or change persists, the cell can undergo irreversible injury.
Adaptations can be physiologic (Normal but beneficial) and
pathological (Harmful).
Types of cellular adaptations:
There are four types of cellular adaptations:
1. Atrophy
2. Hypertrophy
3. Hyperplasia
4. Metaplasia
5. Dysplasia (pre-neoplastic change)
1|Page @ Shoaiba Chaudhary, Medical Pathology Notes
, Atrophy:
Atrophy is defined as a reduction in cell size or number. It leads to the
shrinkage of a tissue or organ.
Mechanisms:
Decreased protein synthesis.
ubiquitin–proteasome system – increases protein degradation.
Reduced workload, reduced blood supply, or a nutritional deficiency.
Examples:
Thymus involution with age. (physiologic atrophy)
Uterus
atrophy during childbirth because of hormonal stimulation (e.g.,
Oestrogen, progesterone decreases)
Hypertrophy:
It is defined as the increase in size of a cell without an increase in cell
number.
Mechanisms:
2|Page @ Shoaiba Chaudhary, Medical Pathology Notes
Cellular adaptations
Introduction:
For the sake of survival, cells need to be adjusted in unfavourable
conditions, to release stress, so this process of reversible change in
number, size, phenotype, or function allows the cell to adapt to that
external stress.
If the stress is removed, the cell returns to its normal conditions. But
if injury or change persists, the cell can undergo irreversible injury.
Adaptations can be physiologic (Normal but beneficial) and
pathological (Harmful).
Types of cellular adaptations:
There are four types of cellular adaptations:
1. Atrophy
2. Hypertrophy
3. Hyperplasia
4. Metaplasia
5. Dysplasia (pre-neoplastic change)
1|Page @ Shoaiba Chaudhary, Medical Pathology Notes
, Atrophy:
Atrophy is defined as a reduction in cell size or number. It leads to the
shrinkage of a tissue or organ.
Mechanisms:
Decreased protein synthesis.
ubiquitin–proteasome system – increases protein degradation.
Reduced workload, reduced blood supply, or a nutritional deficiency.
Examples:
Thymus involution with age. (physiologic atrophy)
Uterus
atrophy during childbirth because of hormonal stimulation (e.g.,
Oestrogen, progesterone decreases)
Hypertrophy:
It is defined as the increase in size of a cell without an increase in cell
number.
Mechanisms:
2|Page @ Shoaiba Chaudhary, Medical Pathology Notes
