Biochemical and pathogenetic mechanisms
Cellular loss is based on a pronounced imbalance between the synthesis and breakdown of substances, with catabolic processes beginning to dominate. Neurotrophins play an important role in these changes: specifically, the nerve growth factor precursor (pro-NGF) is capable of triggering the apoptosis program in denervated structures.
In addition, persistent modifications of the cellular genetic apparatus occur. The appearance of new antigenic properties in the altered tissue is recognized by the body as a distress signal, leading to activation of the immune system. In response, rejection reactions develop with characteristic cellular infiltration.
Intracellular degradation and residual bodies
At the microscopic level, biochemical shifts manifest as profound remodeling of intracellular structures:
- The number of mitochondria and myofilaments decreases.
- The total volume of the endoplasmic reticulum is reduced.
- Autophagic vacuoles actively form, engulfing fragments of damaged organelles.
Undigested cellular debris inside autolysosomes turns into residual bodies. A textbook example is the accumulation of the pigment lipofuscin, an excess of which gives the tissue a characteristic brown tint.
General patterns of organ remodeling
Regardless of the specific localization, the pathological process follows universal rules. The parenchyma of the organ steadily decreases in volume, while stromal elements often persist and replace the dead cells.
- Stromal sclerosis: activated fibroblasts proliferate, forming connective tissue.
- Induration: the combination of parenchymal atrophy and sclerosis leads to organ densification.
- False hypertrophy: apparent enlargement of the organ due to adipose tissue masking the internal loss of working elements.
Atrophy means "catabolism overcomes synthesis": the parenchyma melts away, the stroma becomes sclerotic, and lipofuscin accumulates in lysosomes under the action of pro-NGF.
Class and exam questions
Which biochemical shifts predominate in atrophy?
In affected tissues, catabolic processes sharply intensify, beginning to predominate over the synthesis of new molecules and structures.
What role does the pro-NGF protein play in the development of the process?
The nerve growth factor precursor (pro-NGF) can directly induce apoptosis in denervated cells.
Why does atrophic tissue acquire a brown color?
Due to the massive accumulation of residual bodies—lipofuscin pigment granules inside autolysosomes during the breakdown of intracellular structures.
What else to study on this topic
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- Molecular disorders in hemochromatosis and iron metabolism
- Pathogenesis of cardiac obesity and alcoholic cardiomyopathy
- Features of corticosubcortical atrophy of the CNS
- Impact of complete absence of enteral nutrition on the gastrointestinal mucosa
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