Lecture 5 - Cellular Adaptations

What are reversible/adaptive disorders of growth?

Atrophy

Involution

Hypertrophy

Hyperplasia

What are reversible/irreversible disorders of growth?

Metaplasia

Dysplasia

In hyperplasia and hypertrophy, the tissue is __

Bigger

In atrophy and involution, the tissue is __

Smaller

What is atrophy and involution in general?

Decrease in size or amount of cell, tissue, or organ size/weight after normal growth has been reached

Decreased functional capacity

What is atrophy?

Implies cause by adverse environment

What can cause atrophy?

Lack of/decreased nutrition, blood flow, stimulatory factors, workload/use, innervation, or endocrine stimulation

Pressure atrophy (ex. kidneys, masses)

What is involution?

A physiologic/normal process

When an organ is no longer needed

What is hypertrophy?

Increase in cell SIZE, not cell number

Histologic architecture is normal, but the cells are bigger

Cytoplasm swells due to increased numbers and size of organelles (because organelles are being stimulated)

Hypertrophy is a response to...

An increase in workload or ongoing stimulus (growth stimulus)

What are examples of pathologic hypertrophy?

Hypertrophic cardiomyopathy

Genetic mutations resulting in overdevelopment of muscle

What are examples of physiologic hypertrophy?

Cardiac/skeletal muscle hypertrophy from exercise

Hypertrophy of uterine wall during pregnancy

Compensatory renal hypertrophy after unilateral nephrectomy

Drug metabolism in liver

What is hyperplasia?

Increase in cell number from increased mitotic divisions

Hypertrophy may also be seen concurrently

Increase is in response to increased/ongoing stimulus or to accommodate tissue loss

What does chronic hyperplasia result in?

Increased times genetic information is replicated, which provides more opportunities for mutations (neoplasia)

What typically causes pathologic hyperplasia?

Chronic irritation or hormonal stimulation

What typically causes physiologic hyperplasia?

Often related to sexual development

Response to tissue loss, compensatory

What is metaplasia?

One cell type is replaced by another cell type

Less differentiated reserve/stem cells differentiate along a different line

Within the same germ line, usually epithelial

Not neoplastic

What causes metaplasia?

Chronic irritation or damage

What is an example of metaplasia?

Squamous metaplasia of respiratory epithelium in bronchi from chronic irritation

What is dysplasia?

Abnormal organization and cell maturation (disarray) +/- cellular atypia

What are the 2 major forms of dysplasia?

Developmental/primary: congenital conditions, generally referring to organ/tissue

Acquired/secondary: viral infection, chronic irritation/damage (UV damage)

What is a risk associated with acquired/secondary?

Carries the potential to progress to neoplasia

Is atrophy typically pathologic or physiologic?

Pathologic

Is involution typically pathologic or physiologic?

Physiologic