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

BIOLOGY

SECTION 1. BIOLOGICAL BASES OF HUMAN VITAL ACTIVITY

1.4. ONTOGENETIC LEVEL OF LIFE ORGANIZATION

1.4.3. Biology of Individual Development

Congenital Malformations and Their Classification

Congenital malformations are permanent structural abnormalities of an organ or the entire Organism resulting from impaired morphogenesis during the prenatal period (and occasionally after birth). According to WHO data, the incidence of congenital malformations in various countries ranges from 2.7% to 16.3%. Various sources indicate that congenital malformations account for 20% of infant mortality cases. In Ukraine, over 1,000 infants under one year of age die from congenital malformations annually. Most malformations are caused by monogenic and multifactorial disorders. Examples of specific malformations include: aplasia, the absence of an organ; hypoplasia, underdevelopment of an organ; heterotopia, atypical localization of an organ; stenosis, narrowing of an opening; and atresia, the absence of an opening.

Depending on their Etiology, all congenital malformations are classified as hereditary, exogenous, or multifactorial. Hereditary malformations are caused by Mutations in parental Gametes; exogenous malformations result from environmental factors (teratogens) acting upon the embryo and fetus; and multifactorial malformations stem from a combination of exogenic and endogenic factors. Depending on the stage at which Embryogenesis is disrupted, conditions are categorized as gametopathies, blastopathies, embryopathies, and fetopathies. Gametopathies occur during gametogenesis; blastopathies, at the blastula stage; embryopathies, from the second to the eighth week; and fetopathies, from the ninth week of prenatal development onward. Malformations are further divided into Primary and secondary. Primary malformations are caused by the direct action of a teratogenic agent, whereas secondary malformations are complications of primary ones and are always pathogenetically linked to them.

All congenital malformations are classified into phylogenetically determined and non-phylogenetic. Phylogenetically determined malformations resemble Anatomical Features of ancestral or contemporary chordate groups. Examples include Spina bifida (failure of vertebral arches to fuse), cervical or lumbar Ribs, and cleft palate. These malformations demonstrate the evolutionary genetic connection between humans and other vertebrates. Non-phylogenetic malformations are those that have no analogs among modern vertebrate animals or their ancestors, such as conjoined (siamese) twins.

Ancestral (atavistic) malformations, or atavisms, are the expression of traits characteristic of distant ancestors. These include excessive body Hair, hyperthelia (multiple nipples), and the persistence of an elongated coccyx (tail). The Study of teratogenic factors and congenital malformations underscores the vital need to protect mothers and infants from harmful environmental influences, particularly during the critical teratogenic window (the second through the eighth week of Pregnancy).