Cellular adaptations allow cells to survive and function in response to physiological or pathological stimuli by altering their structure and function. Adaptations include hypertrophy (increase in cell size), hyperplasia (increase in cell number), atrophy (decrease in cell size), and metaplasia (substitution of one normal cell or tissue type for another). Adaptations are reversible changes that occur in stages in response to stress or injury.

1. Cell Adaptation
30. Sept. 2013

2. Adaptations
• Adaptations; are functional and structural
responses to more severe physiologic or
pathologic stimuli,
give new, altered steady states,
allow cells to survive & function
• The adaptive response may consist of
(hypertrophy), (hyperplasia), (atrophy), or
(metaplasia).
• Reversible changes.

3. Stages of cellular response to stress & injurious stimuli.

4. Skeletal muscle hypertrophy

5. Hypertrophy; the muscle cells synthesize more proteins and the number of
myofilaments increases

6. Cardiac
hypertrop
hy involv
left vent.

7. HYPER-TROPHY
IN-CREASE IN SIZE OF CELLS

8. Physiologic hypertrophy of the uterus during pregnancy. A, Gross appearance of a normal
uterus (right) and a gravid uterus (left). B, Small spindle-shaped uterine smooth muscle
cells from a normal uterus (left) compared with large plump cells in gravid uterus (right).

9. HYPER-PLASIA
IN-CREASE IN NUMBER OF CELLS

10. Physiologic Hyperplasia; hormonal hyperplasia
a. Adult breast tissue.
B. lactating breast

11. Bone Marrow hyperplasia in anemia

12. Physiologic Hyperplasia; compensatory hyperplasia

13. Endometrial hyperplasi
(physiological &
pathological)

14. Pathologic Hyperplasia Nodular prostatic hyperplasia, or BPH. The normal prostate is 3 to 4 cm in

15. Nodular prostatic hyperplasia

16. Physiologic Hyperplasia; hormonal hyperplasia
a. Adult breast tissue.
B. lactating breast

17. Hyperplasia is also an important response of connective tissue cells in wound healing

18. ATROPHY?
DE-CREASE IN SIZE OF CELLS
IN CELL SIZE DUE
TO LOSS OF CELL
SUBSTANCE
SHRINKAGE

19. ATROPHY
•
•
•
•
•
•
DECREASED WORKLOAD
DENERVATION
DECREASED BLOOD FLOW
DECREASED NUTRITION
AGING (involution)
PRESSURE

20. Skeletal muscle hypertrophy

21. This is cerebral atrophy in a patient with Alzheimer disease. The gyri are narrowed
and the intervening sulci widened, particularly pronounced toward the frontal lobe
region

22. Right testicular atrophy.

23. METAPLASIA
• A SUBSTITUTION of one NORMAL CELL or
TISSUE type, for ANOTHER
– COLUMNAR SQUAMOUS (Cervix)
– SQUAMOUS COLUMNAR (Glandular)
(Stomach)
– FIBROUS BONE
–WHY?

24. Metaplasia. A, Schematic diagram of columnar to squamous metaplasia.
B, Metaplastic transformation of esophageal stratified squamous epithelium (left) to
mature columnar epithelium (so-called Barrett metaplasia).

25. Metaplasia of the normal esophageal Squamous mucosa, with the appearance of gastric columnar mucosa

26. Metaplasia of laryngeal respiratory epithelium in a smoker.