Cellular Adaptation

Chapter Two Tissue injury Cellular adaptation: Atrophy Hypertrophy Hyperplasia Metaplasia

CELLULAR ADAPTATION • Excessive physiologic stresses. • Some pathologic stimuli. A new, but altered state preserving the viability of the cell.

ATROPHY Decrease in mass of the cell HYPERTROPHY Increase in mass of the cell

ATROPHY • • • • • •

Decreased workload. Loss of innervation. Diminished blood supply. Inadequate nutrition. Loss of endocrine stimulation. Aging

Morphology of atrophy Brown atrophy Reduction in the number of cell organelles. Increase in the number of autophagic vacuoles. Lipofuscin granules (Brown atrophy)

Fig 2-5

HYPERTROPHY • Increased functional demand. • Specific hormonal stimulation.

Fig 2-6

HYPERPLASIA

The myth of Prometheus.

HYPERPLASIA • Physiologic hyperplasia: Hormonal hyperplasia Compensatory hyperplasia • Pathologic hyperplasia: Excessive hormonal stimulation. Effects of locally produced GFs on target cells.

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Fig 2-1

Matrix degradation

PARTIAL HEPATECTOMY

GROWTH FACTORS AND CYTOKINES HGF TGF-α EGF TNF-α IL-6 Others

Priming

ADJUVANTS Norepinephrine Insulin Glucagon Thyroid hormone

Proliferation

GROWTH INHIBITORS TGF-β Others

Groeth lnhibition

Growth factors Adjuvanis

Metaplasia • One adult cell type is replaced by another. • Genetic reprogramming of stem cells. • Epithelial and mesenchymal metaplasia.

•Squamous metaplasia Bronchial epithelia Epithelia in bile duct Cervical epithelia •Intestinal metaplasia of gastric epithelia •Bone metaplasia.