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

ANATOMY, PHYSIOLOGY, PATHOLOGY

SECTION 1. ORGAN. ORGAN SYSTEM. ORGANISM

REGENERATION

Regeneration is the restoration of structural tissue elements to replace damaged or dead ones. Biologically, it is an adaptive process shaped by evolution, inherent to all living things, and aimed at restoring tissue Structure and function. The Significance of regeneration lies in ensuring the material basis of Homeostasis at various levels of the Structural Organization of living matter.

There are two forms of regeneration:

1. Intracellular regeneration — molecular, intraorganellar, and organellar regeneration.

2. Cellular regeneration — based on Direct and Indirect Cell Division.

Types of regeneration:

1. Physiological regeneration.

2. Reparative regeneration.

3. Pathological regeneration.

Physiological regeneration occurs throughout the life of an Organism and is characterized by the renewal of Cells in mucous membranes, serous membranes, Internal Organs, and various Tissues, depending on changing environmental conditions and the execution of specific Functions. Such regeneration occurs continuously, for example, in the integumentary epithelium, where keratinized cells undergo periodic desquamation and are replaced by proliferating cells from deeper layers. Similarly, erythrocytes, leukocytes, and other Blood Cells proliferate and mature in the Bone Marrow.

In highly differentiated cells, where regeneration through cell division is impossible, this process features the periodic renewal of intracellular Organelles (Brain, Heart, etc.).

Reparative (restorative) regeneration is essentially enhanced physiological regeneration within a diseased organism. In other words, during illness, physiological regeneration "transforms" into reparative regeneration, which, after the patient's recovery, returns to the baseline physiological framework.

Reparative regeneration occurs in two forms. In the first case, necrosis resulting from a pathological process is gradually replaced by tissue identical to the destroyed one, and the site of injury disappears without a trace. This type of regeneration is called complete regeneration, or restitution. This form is particularly characteristic of organs and tissues where regeneration occurs exclusively via cellular proliferation (bone marrow, epidermis, mucosal epithelium, etc.).

In other cases, the restoration of impaired functions is ensured through cellular and intracellular hyperplasia occurring not at the injury site, but in the surrounding tissues. The necrotic area itself is gradually filled with Connective Tissue, which subsequently transforms into a scar. This form is called incomplete regeneration, or substitution. This type of regeneration most commonly occurs in organs dominated by the intracellular form of regeneration (Central Nervous system, heart).

Pathological regeneration (i.e., deviating from normal conditions) occurs when the regenerative process is distorted. This is observed in cases of nutritional disorders (protein or vitamin deficiencies), impaired neural regulation, hormonal imbalances, or suppressed immune responses, and is characterized by slowed or distorted regeneration. In such cases, the healing of a wound or bone fracture is delayed and sluggish, leading to non-healing ulcers, keloid scars, pseudoarthrosis (false joints), and other complications. As a rule, pathological regeneration occurs when general and local conditions are unfavorable. The primary general conditions include the patient's age and overall health status. In youth, reparative processes are significantly more intensive than in advanced or old age. In weakened individuals exhausted by illness, reparative processes are sluggish and frequently take the form of pathological regeneration. Conversely, physically healthy individuals typically exhibit robust tissue repair processes. A major role in this is played by the proper regulation of reparative processes by the neuroendocrine system. Local conditions determining the course of regeneration include The Nature of the damaging agent and the Specific characteristics of the tissue injury.