MEDICAL BIOLOGY, HUMAN ANATOMY, PHYSIOLOGY, AND PATHOLOGY - Ya.I. Fedonyuk 2010

ANATOMY, PHYSIOLOGY, PATHOLOGY

SECTION 1. ORGAN. ORGAN SYSTEM. ORGANISM

HYPERTROPHY AND HYPERPLASIA

Hypertrophy refers to an increase in the volume of an organ, tissue, Cell, or intracellular structures accompanied by an enhancement of their function. Hyperplasia refers to an increase in the number of Cells, intracellular structures, and interstitial tissue. Both processes frequently

occur concurrently. Hypertrophy and hyperplasia have a pronounced adaptive significance aimed at compensating for the Functions of a damaged or overworking organ or system.

Taking into account The ratio of adaptation and compensation processes, a distinction is made between hypertrophy of an adaptive nature (neurohumoral form, hypertrophic growths) and a compensatory nature (working compensatory form and vicarious, or substitute, form).

Neurohumoral (hormonal) hypertrophy can be generalized or focal in nature. In the first case, it affects the entire Organism, while In the second, it involves individual Organs or Tissues. An example of generalized hypertrophy is acromegaly, a disorder in which, against the Background of impaired Nutrition, There is a simultaneous increase in the volume and size of the protruding PARTS OF THE face (Nose, lower jaw, supraorbital ridges) and the peripheral parts of the limbs. If the disease manifests at a young age, symptoms of general gigantism develop (acromegalic gigantism). Morphologically, this hypertrophy is based on the proliferation of all tissues comprising the enlarging parts, including an increase in the size of Internal Organs. The condition is triggered by elevated activity of the anterior Pituitary Gland with Excessive production of somatotropic hormone.

An example of focal hypertrophy is gynecomastia (from Greek gyne — woman, mastos — breast), which most commonly results from testicular atrophy, as well as glandular hyperplasia of the endometrium. The latter is based on a significant thickening of the uterine mucosa (up to 5 times the normal rate).

Hypertrophic growths involve one or more adjacent tissues. These growths are observed in chronic inflammation (polyps on mucous membranes) and in cases of impaired Lymph flow in the lower extremities leading to stasis (elephantiasis). False and compensatory vacuum hypertrophy also belong to this type of pathological process.

In false hypertrophy, the volume of an organ increases due to the proliferation of interstitial tissue, while the function of the organ is not compensated. Moreover, in false hypertrophy, the specialized parenchyma of the organ often undergoes atrophy, and its function declines. For instance, atrophy of Muscle fibers is accompanied by a marked proliferation of adipose tissue, which overall creates the impression of an overall increase in muscle bulk.

Vacuum hypertrophy represents the proliferation of connective or adipose tissue in response to parenchymal atrophy of internal organs, such as fat accumulation around atrophied Kidneys or the overgrowth of the cranial flat bones during cerebral atrophy.

The group of compensatory processes predominantly includes Two Types of hypertrophy: working compensatory hypertrophy and vicarious (substitute) hypertrophy.

Working (compensatory) hypertrophy occurs under conditions of functional insufficiency in a given tissue or organ, aiming to compensate for it during various pathological processes or diseases. The physiological prototype of such hypertrophy is the enlargement of somatic Muscles in physical laborers and athletes (gymnasts, wrestlers). Left Ventricular Hypertrophy of The Heart is observed in aortic valve stenosis resulting from inflammatory processes. Similar changes develop in Hypertension and atherosclerosis. In esophageal strictures, the muscular layer thickens in the segments located above the narrowing.

Vicarious (substitute) hypertrophy is observed following the destruction or surgical removal of one of a pair of organs. Under these conditions, the remaining organ compensates for the functional impairment through intensified activity (kidneys, Lungs, Testes).

Regenerative hypertrophy occurs when a portion of a tissue or organ is destroyed. For example, regenerative hypertrophy of surviving Muscle tissue develops in myocardial infarction. In this case, the area of necrosis (infarction) is replaced by scar tissue, while cardiomyocyte hypertrophy is underpinned by the hyperplasia of their intracellular structures.