Growth Adaptatsis.........................

cell injury and cell death

1. Growth Adaptations
Dr Mishal Safi

2. Basic Principles

●Organ is in homeostasis with the physiologic
stress placed on it.
●Increase, decrease or change in stress on an
organ can result in growth adaptations.

3. Hyperplasia & Hypertrophy

●Increase in stress leads to increase in organ
size.
●Occurs via increase in size and/or number of
cells

5. Hypertrophy

●Increase in cell size
●Involves gene activation, protein synthesis
and production of organelles

6. Hyperplasia

●Increase in number of cells
●Involves production of new cells from stem
cells

8. ●Hypertrophy and hyperplasia usually occur
together e.g during pregnency.
●Permanent tissues can not form new cells
and undergo hypertrophy

10. ●Pathologic hyperplasia can lead to dysplasia
and cancer
●Example : Endometrial hyperplasia
●Exception : Benign prostatic hyperplasia

11. Atrophy
●Decrease in Stress leads to decrease in
organ size
●Occurs via decrease in size and number of
cells

14. ●Decrease in cell number occurs via
apoptosis
●Decrease in cell size occur via
Ubiquitin-proteosome degradation of
cytoskeleton and autophagy of cellular
components

15. Metaplasia
●Change in stress on organs leads to change in
cell type
●Most commonly involves surface epithelium
●Metaplastic cells are better able to handle new
stress

16. Barrett’s Esophagus

●Barrett’s esophagus is a classic example of metaplasia in which
the normal stratified squamous epithelium of the esophagus is
damaged by acid reflux, causing it to undergo metaplasia and
convert into columnar epithelium.

17. ●Barrett esophagus is a classic example

18. ●Metaplasia occurs via reprogramming of stem
cells
●Metaplasia is reversible if stress is removed
●Untreated metaplasia can progress to
dysplasia and cancer.

19. Vitamin A deficiency can also result in metaplasia

20. Dysplasia
●Disordered cellular growth
●Refers to proliferation of precancerous cells
●Arises from longstanding pathologic
hyperplasia or metaplasia
●Dysplasia is reversible
●If left untreated will convert into cancer

22. Aplasia and Hypoplasia
●Aplasia is failure of cell production during
embryogenesis e.g renal agenesis

●Hypoplasia is a decrease in cell production
during embryogenesis e.g streak ovary in
Turner’s syndrome