Cellular Adaptation
Cellular adaptation refers to changes in the
number, size, or type of cells in response to
alterations in their environment.
These adaptations allow cells and tissues to
survive, maintain function, or minimize
damage under stressful conditions.
Adaptations are typically protective
mechanisms aimed at maintaining
homeostasis. However, if the stress persists or
becomes excessive, these adaptations can fail,
leading to cell injury or death.
Dr. MUHAMMAD IMRAN
Assistant Professor
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Hyperplasia
Hyperplasia occurs in tissues capable of mitotic division. It is often driven
by growth factors, hormones, or other signaling molecules that stimulate cell
proliferation.
Pathologic Hyperplasia
Physiologic Hyperplasia Endometrial Hyperplasia: Excessive
and prolong hormonal stimulation
Hormonal: Example—mammary (e.g., estrogen without progesteron)
gland hyperplasia during lactation. leads to an increase in the number of
cells lining the uterus and can
Compensatory: Example—liver predispose to pyometra.
regeneration after partial
hepatectomy. Prostatic Hyperplasia: Benign
prostatic hyperplasia (BPH) in older
male is often driven by androgens
(testosterone). preencoded.png
Prolactin, Estrogen, Progesterone,
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Atrophy
Atrophy is a decrease in the size of cells, leading to a reduction in the size of
the organ or tissue. It occurs due to decreased workload, inadequate nutrition,
reduced blood supply, loss of hormonal stimulation, or aging.
Physiologic Atrophy Pathologic Atrophy
Example—the thymus gland Example—muscle atrophy due to
atrophies with age. disuse or denervation.
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Metaplasia
Metaplasia is a reversible change in which one adult cell type is replaced by
another adult cell type. It is often a response to chronic irritation or injury, and
the new cell type is better suited to withstand the adverse environment.
Example
The lining of the trachea in smokers may undergo squamous metaplasia,
replacing the normal ciliated columnar epithelium with stratified squamous
epithelium, which is more resistant to the damaging effects of smoke.
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• Grossly –Difficult to appreciate grossly preencoded.png
Dysplasia
Dysplasia is abnormal development or growth of cells, often characterized by
changes in cell size, shape, and organization. It is considered a precancerous
condition, as it can progress to malignancy if the underlying stimulus is not
removed.
Example
Cervical dysplasia is a precancerous condition that can progress to cervical cancer
if left untreated.
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Cellular Adaptation: Key
Points
1 Adaptive Responses
Cellular adaptations are typically protective mechanisms
aimed at maintaining homeostasis.
2 Reversible Changes
Many cellular adaptations are reversible if the underlying
stimulus is removed.
3 Stress and Injury
If the stress persists or becomes excessive, these adaptations
can fail, leading to cell injury or death.
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