Human Anatomy, Part 1 - K. A. Dyubenko, A. K. Kolomiysev, Yu. B. Chaykovsky 2002

General Part
General Information on the Structure of the Human Body
The Concept of Norm, Variants of Norm, and Anomalies

It is well known that the overall Structure OF THE human body, its parts, Organs, and systems exhibits certain—and sometimes significant—differences among individuals. At the same time, thanks to the adaptive (adaptatio) Properties of the Organism, its full functionality is maintained even under extreme variants of individual Variability. Thus, the range within which the individual CHARACTERISTICS OF THE morphofunctional state can ensure the performance of biological and social Functions is defined as the norm. It depends on both hereditary factors and environmental influences. When the latter do not exceed the adaptive capacity of the organism, the normal state is preserved. Excessive environmental influences may cause deviations from the norm, known as variants (from Lat. variatio - modification), which generally do not significantly impair bodily functions.

The most persistent congenital deviations from normal Structure and function are termed anomalies (from Greek anomalia - irregularity). Deviations acquired after birth should not be classified as anomalies. Congenital defects and developmental malfunctions impair the body's functions, and some of them are incompatible with life.

The causes of anomalies are environmental factors that lead to Congenital Malformations. These factors most frequently disrupt normal development during the so-called critical periods, specifically the period of blastocyst implantation (days 7–12) and the period of placentation (weeks 3–6). A thorough knowledge of anatomical variants and anomalies is essential for clinical practice.