MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY AND PATHOLOGY - Y.I. Fedoniuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

SECTION 1. ORGAN. ORGAN SYSTEM. ORGANISM

INJURY

1. Dystrophy

Dystrophy is a complex pathological process driven by impaired tissue METABOLISM that leads to structural alterations. Therefore, dystrophy is considered a form of cellular injury. At the core of injury lies a disruption of trophic processes, or Nutrition. The trophic supply of Cells and Tissues is maintained by cellular and extracellular mechanisms. Cellular mechanisms involve intrinsic autoregulation of The Cell, whereas extracellular mechanisms rely on transport factors (Blood, Lymph) and regulatory factors (neural, endocrine). Thus, disorders in either of these mechanisms can act as the direct cause of dystrophy development.

The primary pathogenetic mechanisms leading to dystrophy include infiltration, decomposition, distorted synthesis, and transformation.

Infiltration refers to the accumulation of various substances within cells or the Extracellular matrix that cannot be utilized due to enzymatic system dysfunctions (for instance, Cholesterol infiltration of arterial walls in atherosclerosis, or the appearance of fat droplets in hepatocytes during Fatty Liver disease).

Decomposition is The breakdown of cellular ultrastructures and intercellular substance, accompanied by the accumulation of decay products within them. For example, Hypoxia-induced breakdown of intracellular membranes composed of lipoprotein complexes results in an excess of either Proteins or fats accumulating inside the cell, leading to protein or fat dystrophy respectively.

Distorted synthesis involves The production of abnormal substances within cells or the extracellular matrix that are not normally present (such as amyloid or alcoholic hyaline).

Transformation is a process whereby, due to specific triggers, substances characteristic of one type of metabolism are formed instead of another—for instance, proteins transforming into fats or CARBOHYDRATES.

Depending on the severity of metabolic impairment and the extent of morphological changes, dystrophies can be either reversible or irreversible. In the latter case, the pathological process progresses until cell or tissue death (necrosis) occurs. Consequently, irreversible dystrophies culminate in necrosis.

The Classification of dystrophies is based on specific criteria.

I. Depending on the localization of the process:

1) parenchymal (cellular);

2) mesenchymal (stromal-vascular, extracellular);

3) mixed.

II. Depending on which type of metabolism is predominantly impaired:

1) protein;

2) lipid;

3) carbohydrate;

4) mineral.

III. Depending on The Influence of genetic factors:

1) acquired;

2) hereditary.

IV. According to the spread of the process:

1) generalized;

2) local.

Parenchymal dystrophies occur within cells and are characterized by the accumulation of proteins, fats, and carbohydrates in their Cytoplasm, which is accompanied by functional decline and specific structural alterations.

Depending on the type of metabolic disorder involved, parenchymal dystrophies are classified into protein, lipid, and carbohydrate dystrophies.

Mesenchymal dystrophies develop due to metabolic disturbances in the interstitial Connective Tissue, which forms the stroma of Organs and is a component of vascular walls. Pathological alterations in Protein metabolism within the connective tissue lead to several forms of protein dystrophy (dysproteinosis): mucoid and fibrinoid Swelling, hyalinosis, and amyloidosis.

Pathological Changes in the metabolism of neutral fat, cholesterol, or cholesterol esters result in mesenchymal lipid dystrophies (lipidoses).

Mesenchymal carbohydrate dystrophies are primarily associated with impaired glycoprotein metabolism, manifesting as the accumulation of a thick, mucus-like substance replacing connective tissue, Cartilage, and adipose tissue.

In mixed dystrophies, Metabolic Disorders occur simultaneously in both cells and the intercellular substance. This type of dystrophy stems from a breakdown in the Metabolic pathways of complex proteins and minerals. Complex proteins are compounds consisting of a protein bound to non-protein components. In Chromoproteins, the protein is bound to pigments; in Nucleoproteins, to Nucleic Acids; in Lipoproteins, to Lipids; and in Glycoproteins, to carbohydrates. Among the disorders of complex protein metabolism, disturbances involving chromoproteins (endogenous pigments) play a major role. For instance, aberrations in bilirubin metabolism lead to jaundice.

Disturbances in Mineral Metabolism arise from inadequate intake of salts into the body, or from pathological defects in their excretion or the distribution of ions between the intracellular and extracellular environments.