Cellular Adaptation- PRELIMS L3

ADAPTATION

Reversible changes in size, number, phenotype, metabolic activity, or functions of cells in response to changes in their environment.

ABNORMALITIES IN CELL GROWTH

1. Retrogressive changes

2. Progressive changes

3. Degenerative changes

RETROGRESSIVE CHANGES

Organs or tissues are smaller than normal

TWO MAIN TYPES OF RETROGRESSIVE CHANGES

1. Developmental changes- present at birth

2. Atrophy- acquired

DEVELOPMENTAL CHANGES

• Aplasia

• Agenesia

• Hypoplasia

• Atresia

APLASIA (DC)

• Incomplete or defective development of tissue or organ, represented only by a mass of fatty or fibrous tissue, bearing no resemblance to the adult structure

• Most commonly seen in one paired structures such as kidneys, gonads, adrenals

AGENESIA (DC)

Complete non-appearance of the organ

HYPOPLASIA (DC)

Failure of an organ to reach or achieve its full mature or adult size due to incomplete development

ATRESIA (DC)

Failure of an organ to form an opening

ATROPHY

• Decreased cell and organ size, as a result of decreased nutrient supply of disuse

• Decreased cell size and total number of cells or both

TYPES OF ATROPHY

1. Physiologic atrophy

2. Pathologic atrophy

3. Starvation atrophy

PHYSIOLOGIC ATROPHY

During normal development

• In adult:

  ⚬ Thymus

  ⚬ Uterus during parturition

  ⚬ Breast tissue after lactation

PATHOLOGIC ATROPHY

Depends on the basic cause & maybe generalized or localized

STARVATION ATROPHY

Wasting of muscle

COMMON CAUSE OF ATROPHY

1. Decreased workload

2. Loss of innervation

3. Diminished blood supply

4. Inadequate nutrition

5. Loss of endocrine stimulation

6. Pressure

PROGRESSIVE CHANGES

• Organs or tissues are larger than normal

  • Hypertrophy

  • Hyperplasia

HYPERTROPHY

• Increased cell size and organ size

• No new cells. Just Increased in size due to synthesis of more structural components

TYPES OF HYPERTROPHIES

1. True hypertrophy

2. False hypertrophy

3. Compensatory hypertrophy

TRUE HYPERTROPHY

Due to increased workload and endocrine stimulation

FALSE HYPERTROPHY

Due to edema fluid and connective tissue proliferation

COMPENSATORY HYPERTROPHY

Involves one of the paired organs when the other opposite organ has been removed or suffered functional insufficiency

HYPERLASIA

• Increased in size of an organ or tissued due to increase in the number of cells resulting from growth of new cells

• Does not always increase the size of an organ

• Hypertrophy and Hyperplasia co-exist in many organs

• Only if cells is dividing in response to hormones and growth factor

PATHOLOGICAL HYPERPLASIA

Excess hormones & GF

PHYSIOLOGICAL HYPERPLASIA

Growth of normal cells in response to a specific stimulus and remains subject to normal regulatory control mechanisms

DEGENERATIVE CHANGES

Changes due to aberration of cellular growth

• Metaplasia

• Dysplasia

• Anaplasia

• Neoplasia

METAPLASIA

• Replacement of one type of cell with another type of cell

• Often in response or adaptation to chronic injury.

• Differentiated cell type is replaced by similarly differentiated cell

• Usually induced by altered differentiation pathway of tissue stem cells; may result in reduced functions or increased propensity for malignant transformation.

DYSPLASIA

• Literally means “disordered growth”

• Regressive alteration in adult cells manifested by variation in size, shape and orientation.

• Premalignant change

ANAPLASIA

• Differentiation

• Marked regressive change in adult cells towards a more embryonic cell type.

• Criterion towards malignancy

NEOPLASIA

• Continuous abnormal proliferation of cells without control.

• Overproduction of cells leads to mass or tumor.