Lecture # 17
CELL ADAPTATION - 2
Dr. Iram Sohail
Assistant Professor
Pathology
College Of Medicine
Majmaah University
CLINICAL SIGNIFICANCE
OF
CELL ADAPTATION
OBJECTIVE
• Explain the clinical significance of cell
adaptation
• When cell faces any physiologic stresses or
pathologic stimuli, first the cell goes to
adaptation.
• Adaptation means acquiring a new steady
state and preserve the viability & function of
cell.
CLINICAL SIGNIFICANE
• Adaptation is very necessary for our body to
adjust in a new environment and also to
preserve the function and viability of cells.
Examples of clinical significance
of hypertrophy
1. Uterine hypertrophy during pregnancy
• As the pregnancy progresses, the growing
fetus requires more space for his
development.
• Uterine smooth muscle cannot replicate
(cannot divide and increase in numbers)
• So that’s why under the stimulation of
pregnancy hormone (estrogen) they only
increase in size (hypertrophy).
2. Skeletal muscle hypertrophy in weightlifter
• In response to increased workload during
weightlifting and exercise, the individual
skeletal muscle cell will undergo hypertrophy
and shows a strong physique.
3. Heart enlargement in hypertension & aortic
valve disease
• In hypertension & aortic valve disease, heart has to
contract forcefully to fulfill the requirement of body.
For this forceful contractility the cardiac muscle cells
goes into hypertrophy.(because they cannot divide
and can’t go into hyperplasia)
Examples of clinical significance
of hyperplasia
1. Hyperplasia of female breast at puberty &
pregnancy
• Under the influence of female hormones, the
glandular epithelium of breast proliferates at
puberty and during pregnancy.
2. Compensatory hyperplasia in liver
• This type of hyperplasia occurs when a portion
of an organ is removed or diseased.
Example
• When some portion of liver is removed in the
process of transplantation, the remaining
portion of liver starts replication and
eventually the normal weight of liver will be
restored.
• The stimulus for this restoration is growth
factors, produced by the remaining liver cells.
• After restoring the normal weight, the growth
is turned off by growth inhibitors.
3. Endometrial hyperplasia
• The endometrial lining of uterus is maintained
at a normal thickness by growth stimulatory &
growth inhibitory pituitary and ovarian
hormones.
• When this hormonal balance is disturbed by
any disease, the thickness of endometrium is
increased and eventually results in
endometrial hyperplasia.
• This endometrial hyperplasia can change into
cancer.
Examples of clinical significance
of atrophy
1. Loss of innervation
– In polio virus ----- loss of innervation ----- atrophy
of limb
2. Loss of blood supply
– In atherosclerosis ------ atrophy of brain
3. Decreased workload
– In fracture ------ because of immobilization
------- atrophy of limb
4. Ageing
– Brain & other body parts atrophy
5. Loss of endocrine (hormonal) stimulation
– Postmenopausal atrophy of female genital
organs
Examples of clinical significance
of metaplasia
1. Metaplasia in smokers
• In smokers, the normal columnar ciliated
epithelium of respiratory tract is replaced by
stratified squamous epithelium.
• This metaplasia will enable respiratory tract to
survive under tough circumstances that has
created by cigarette smoke. It may lead to
lung cancer in future.
2. Vitamin A deficiency
– causes metaplasia in respiratory tract and eye.
3. Esophageal metaplasia
• In gastric esophageal reflux disease, the
normal squamous epithelium of lower
esophagus is replaced by columnar
epithelium.
4. Bone metaplasia
– Sometimes bone is formed in soft tissue especially
after injury.