CELLULAR

BASIS OF

DISEASE(Cell Injury, Cell Death, and

Adaptations

Prof. Mark Anthony I. Jose, MSc.

Overview of Cellular Responses

to Stress and Noxious Stimuli

– Cells are active participants in their environment, constantly

adjusting their structure and function to accommodate changing

demands and extracellular stresses.

– Cells tend to maintain their extracellular milieu within a fairly

narrow range of physiologic parameters; that is they maintain

normal homeostasis.

– The principal adaptive responses are hypertrophy, hyperplasia,

atrophy, and metaplasia.

Adaptation VS Injury

Cellular Adaptation to

Stress

HYPERTROPHY

– Hypertrophy is an increase in the size of

individual cells, in response to a stimulus or

injury. Increased workload leads to increased

protein synthesis & increased size & number of

intracellular organelles which, in turn, leads to

increased cell size. The increased cell size leads to

increased size of the organ.

HYPERPLASIA

– Is an increase in the absolute number of cells, in

response to a stimulus or persistent cell injury. It

can lead to an increase in the size of the organ. It

is usually caused by hormonal stimulation. It can

be physiological as in enlargement of the breast

during pregnancy or it can pathological as in

endometrial hyperplasia.

Two (2) forms of Physiologic

Hyperplasia

Hormonal Hyperplasia

– Exemplified by the proliferation of

the glandular epithelium of the

female breast at puberty and

during pregnancy.

Compensatory Hyperplasia

– Occurs when a portion of the

tissue is removed or diseased.

– For example, when a liver is

partially resected, mitotic activity

in the remaining cells begin as

early as 12 hours later, eventually

restoring to its normal weight

ATROPHY

– Shrinkage in the size of the cell (with or without accompanying

shrinkage of the organ or tissue). Atrophied cells are smaller than

normal but they are still viable. Atrophy can be caused by:

A. Disuse

B. Undernutrition

C. Decreased endocrine stimulation

D. Denervation

E. Old age

METAPLASIA

– A reversible change in which one mature/adult cell type (epithelial

or mesenchymal) is replaced by another mature cell type of the

same category. Metaplasia is the replacement of one

differentiated tissue by another differentiated tissue. There are

different types of metaplasia.

Osseous Metaplasia