Cellular Adaptations
ability of cells to respond to various types of stimuli and adverse environmental changes
Atrophy(decrease in cell size)
Hypertrophy(increase in cell size)
Hyperplasia(increase in cell number)
Metaplasia(change in cell type): Replacement of one differentiated cell type with another mature differentiated cell type that is not normally present in that tissue.
Dysplasia (increase in abnormal cell): Dysplasia is not cancer, but it may sometimes become cancer.
Terminologies used in Disturbances of Cell Growth which are not adaptations
Agenesis refers to the failure of an organ to develop during embryonic growth and development
Hypoplasia is the underdevelopment or incomplete development of a tissue or organ. It is technically not the opposite of hyperplasia (too many cells). Hypoplasia is a congenital condition, while hyperplasia generally refers to excessive cell growth later in life.
Aplasia is a birth defect where an organ or tissue is wholly or largely absent. It is caused by a defect in a developmental process.
2. Learning Outcomes
• By the end of the lecture you should be able to:
• Define Cell injury
• Enlist Cellular Response of cells
• Define and Discuss about the different types of adaptation e.g. Atrophy,
Hypertrophy, Hyperplasia, Metaplasia, Dysplasia
3. Cellular Injury
At some point, a stimulus exceeds the cell‘s ability to
adapt, causing cell injury to occur.
Cell Injury: Any change resulting in loss of the ability to
maintain the normal or adapted homeostatic state
4. Cellular Response
The cells react to an adverse influence by:
Cellular
adaptations
Atrophy,
hypertrophy,
hyperplasia etc.
Reversible cell
injury/
Degeneration
Cell Swelling
Fatty Change etc.
Irreversible cell
injury
Necrosis, Apoptosis
6. ABILITY OF CELLS TO RESPOND TO VARIOUS TYPES
OF STIMULI AND ADVERSE ENVIRONMENTAL
CHANGES
Cellular adaptation
CELLS RESPOND TO
HOMEOSTATIC CHALLENGES
THROUGH ADAPTATION
7. Cellular Adaptations
•Atrophy(decrease in cell size)
•Hypertrophy(increase in cell size)
•Hyperplasia(increase in cell number)
•Metaplasia(change in cell type): Replacement of one
differentiated cell type with another mature differentiated cell
type that is not normally present in that tissue.
•Dysplasia (increase in abnormal cell): Dysplasia is not cancer,
but it may sometimes become cancer.
11. Muscle - Atrophy in a male rat from a chronic study. Individual
hypereosinophilic muscle fibers of reduced diameter are sometimes
surrounded by clear spaces.
12. Skeletal muscle - Atrophy in a male mouse from a subchronic study. Note
the reduction in myofiber diameter of the affected fibers (top) compared
with the more normal myofibers along the bottom.
16. Pathologic hypertrophy. Liver from a dog with enlarged hepatocytes
having increased pale, “waxy” cytoplasm (a*), due to profound increase
in smooth endoplasmic reticulum
17. Skeletal muscle - Hypertrophy in a male rat from a subchronic study.
Large, hypertrophic fibers (arrows) are adjacent to longitudinally split
muscle fibers (arrowheads).
35. Terminologies used in Disturbances of Cell Growth
which are not adaptations
• Agenesis refers to the failure of an organ to develop during embryonic
growth and development
• Hypoplasia is underdevelopment or incomplete development of a tissue or
organ. It is technically not the opposite of hyperplasia (too many cells).
Hypoplasia is a congenital condition, while hyperplasia generally refers to
excessive cell growth later in life.
• Aplasia is a birth defect where an organ or tissue is wholly or largely absent.
It is caused by a defect in a developmental process.
