Ontogenesis of man. Short description. Ontogenesis of the human nervous system

Human ontogeny is a process of individual development from the moment of conception to death. The main characteristics are closely interconnected qualitative and quantitative transformations, defined specifically for each stage.

The concept of "ontogeny" was first introduced by Haeckel (German biologist) in 1866. Different representatives of the animal world have different development. Thus, the ontogeny of insects occurs in a larval type with subsequent metamorphosis. In animals laying eggs, individual development predominantly occurs in eggs laid in the external environment. Placental animals, human development is prenatal. In this case, the process is divided into three periods: postembryonic, embryonic, proembryonic.

The latter is characterized by the formation and development of male and female gametes - gametes, with the fusion of which a fertilized egg is formed.

The ontogeny of a person in the embryonic period consists of the stages of the embryo and the fetus.

The post-embryonic period begins after the birth is authorized. This stage lasts a lifetime, ending with death. The post-embryonic ontogeny of man is divided into age stages. At each stage the body undergoes its anatomical and physiological changes. According to experts, the most vulnerable and critical periods are the climacteric (the time of extinction of sexual functions) and pubertal (the stage of puberty). These are the main features of human ontogeny.

The early stages of embryonic life are characterized by the birth of the central nervous system. Ontogenesis of the nervous system in humans continues and during the first years after birth.

In the dorsal department, the embryo forms a plate. Later, a neural groove is formed, and later - a neural tube.

For a week-old embryo, there is an insignificant thickening of the tube in the oral section. By the third week in the head region three brain bubbles (primary) are formed: posterior, middle, anterior. The main parts of the brain are formed from them (rhomboid, medium, terminal). Subsequently, dismemberment occurs in two blisters (anterior and posterior). From the final hemisphere of the brain and the nucleus (subcortical).

By the third month of embryonic development the main sections of the central nervous system begin to be determined. These include the large hemispheres, cerebral ventricles, trunk, spinal cord. By the fifth month the main furrows are allocated in the cortex (hemispheres). After four weeks, the prevalence (of a functional nature) of the higher divisions over the stem-spinal regions is determined.

Nerve cells of the embryo and newborn are concentrated in white matter and on the surface of the hemispheres. In connection with the increase in surface, the migration of cells into gray matter begins.

In comparison with an adult, the neonatal occipital lobe in the cortex has a relatively large size. The ontogeny of man in the first five to six years after birth has a certain specificity. During this period, the greatest changes occur in the topographical location, shape and number of hemispheric convolutions. By fifteen - sixteen years there is a certain similarity with adults.

For the postnatal period, changes in the spinal cord are also characteristic. In a newborn, it is longer than for an adult. The spinal cord grows to about twenty years.

In a newborn, the nervous system is myelinated (covered with a membrane) insufficiently, the arrangement of bundles of nerve fibers is uneven, and they themselves (bundles) are rare.

The functioning of the nervous vegetative system begins in man from birth. In the postpartum period there is a fusion in separate sites and the formation of plexuses in the nervous sympathetic system.