Anatomy and Physiology of the Visual System

Morphological basis and evolutionary structural features

Comparative anatomy and embryology explain the structural organization of body systems through evolutionary mechanisms. The accessory structures of the eye feature the vestigial third eyelid — an anatomical formation that lost its original functional significance in phylogenesis but persists in all representatives of the human species. Such vestiges serve as indirect evidence of divergence alongside the coccyx, wisdom teeth, and appendix.

The development of structures is subject to Von Baer's law of embryonic resemblance: at early stages of ontogenesis, embryos repeat the basic features of ancestral forms, developing a notochord and neural tube, and subsequently diverge sequentially. As studies have established, embryos repeat the structures of ancestral embryos rather than their definitive forms. Disruption of the reduction of embryonic primordia can lead to atavisms — rare returns to ancestral traits.

Physiology of visual strain in professional activities

In modern labor physiology, the proportion of visual tasks requiring prolonged concentration and fixation of gaze on microstructures is steadily increasing. Such functional overloads are typical for a number of specialists:

• assemblers of high-precision equipment;
• researchers working with an optical microscope;
• watchmaking masters;
• jewelers;
• dentists.

Prolonged functional overstrain of the visual organs occurs in close connection with constant tonic tension of the skeletal muscles. If professional activity requires continuous visual control of small details, the adaptive reserves of the analyzer are depleted. This naturally entails a decrease in functional performance and creates the groundwork for the development of occupational pathology.

Combined influence of working posture and ergonomic principles

Performing precision visual manipulations is almost always accompanied by a fixed working posture — most often sitting in a stooped position or standing.

To prevent fatigue and deformities, an ergonomic complex is necessary:

1. Workplace organization: an anatomical chair with seat height adjustment via a screw column, a backrest with vertical and anteroposterior adjustment, armrests for the hands, and a footrest.
2. Work and rest regimen: mandatory alternation of postures, introduction of regulated breaks, performance of occupational exercises, and self-massage of the upper extremities in the first half of the work shift.

Physical principles of tissue conduction and systemic homeostasis

Functional assessment of organs is based on the laws of sound wave propagation in heterogeneous and dense media. The physical basis of mechanical wave conduction is determined by the structural organization of tissue:

• Heterogeneous medium (e.g., air-containing cavities) has poor resonating properties and dampens vibrations.
• Acouistically homogeneous medium (densified tissues) ensures reliable conduction of phenomena to the body surface.

Turbulent flow movement and tissue vibrations reflect the dynamics of functional systems. However, the resources of any living organism are finite. Natural aging, physiological wear and tear, and senility naturally lead to the gradual fading of all functions and the end of the life cycle by non-violent physiological death.

Class and exam questions

What else to study on this topic

• The method of triple parallelism and comparative anatomical homologies of the forelimb
• Karl Ernst von Baer's law of embryonic resemblance and Severtsov's amendments to the biogenetic law
• Physical foundations of acoustic conduction and the emergence of turbulent murmurs during breathing
• Classification of manners and categories of non-violent and violent death
• Mechanical occupational hazards: comparative pathology of sitting, standing, and lying postures

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.