CELLULAR ADAPTATIONS AND

INJURY

Dr Vijay Shankar S

• Introduction • Cellular adaptations• Types of adaptations • Mechanism • Examples

Pretest

1. In smokers ,the ciliated columnar epithelium of trachea and bronchi are replaced by squamous epithelium. This is an example of

A. Hyperplasia B. Dysplasia C. Metaplasia D. Hypertrophy

• 2. Skin ‘warts’ is an example for A. Hyperplasia B. Dysplasia C. Metaplasia D. Hypertrophy

NORMAL CELL(HOMEOSTASIS)

STRESS

ADAPTATION CELL INJURYINABILITY TO

ADAPT

REVERSIBLE INJURY

MILDTRANSIENT

SEVEREPROGRESSIVE

IRREVERSIBLE INJURY

NECROSIS APOPTOSISCELLDEATH

CELLULAR ADAPTATIONS

ATROPHYHYPERTROPHY HYPERPLASIA

METAPLASIA

• New , steady altered state

• Allows them to survive

• Continue to function

• In abnormal environment

ATROPHY

• Decrease in the number and size of the cells of an organ

• Mechanism :Decreased protein synthesis andincreased protein degradation

in the cells

ATROPHY

PHYSIOLOGICATROPHY

PATHOLOGIC ATROPHY

1. Disuse atrophy

2. Nutritional/starvation atrophy

3. Ischemic atrophy

4. Neuropathic

5. Loss of endocrine stimulation

6. Pressure atrophy

1. Decrease in size of uterus after parturition

2. Brain, with ageing

HYPERTROPHY

• Increase in the SIZE of the parenchymal cells in the organ

• Cause : • Increased functional demand or• By stimulation of hormones and growth factors

• Mechanisms :• Increased production of cellular proteins.

HYPERTROPHY

PHYSIOLOGICHYPERTROPHY

PATHOLOGIC HYPERTROPHY

1. Skeletal muscle

2. Cardiac muscle

3. Smooth muscle

4. Compensatory hypertrophy

1. Enlarged size of the uterus in pregnancy

HYPERPLASIA

• Increase in the NUMBER of cells in an organ

• It takes place if the cell population is capable of dividing

• Mechanism :• Results from growth factor induced proliferation of

mature cells or• Increased output of new cells from stem cells.

HYPERPLASIA

PHYSIOLOGICHYPERPLASIA

PATHOLOGIC HYPERPLASIA

1. Hormonal excess- endometrial, prostate

2. Certain viral infections:papillomavirus- warts

1. Enlarged size of the uterus in pregnancy

2. Breast – puberty pregnancy, lactation

Compensatory hyperplasia

Regeneration of liver, kidney and skin

Marrow hyperplasia

METAPLASIA

• It is a reversible change in which one differentiated cell type (epithelial or mesenchymal) is replaced by another cell type

Mechanism

• Due to REPROGRAMMING of the precursor cells, present in the normal tissues.

METAPLASIA

EPITHELIAL METAPLASIA

MESENCHYMAL METAPLASIA

1. OSSEOUS METAPLASIA

1. Arterial wall

2. Myositis ossificans

3. Stroma of tumor

4. Cartilage of larynx in elderly

2. CARTILAGENOUS METAPLASIA

1. Healing of fractures

1. SQUAMOUS METAPLASIA

1. Bronchus

2. Uterine cervix

3. Gall bladder

4. Renal pelvis

2. COLUMNAR METAPLASIA

1. Barrett’s esophagus

2. Healed gastric ulcer

Post test

1. In smokers ,the ciliated columnar epithelium of trachea and bronchi are replaced by squamous epithelium. This is an example of

A. Hyperplasia B. Dysplasia C. Metaplasia D. Hypertrophy

C

• 2. Skin ‘warts’ is an example for A. Hyperplasia B. Dysplasia C. Metaplasia D. Hypertrophy

A