Age-related changes

Gerontology is a science that studies the aging process, age-related changes in humans: its biological, medical, social, psychological, hygienic and economic aspects (the science of aging).

The sections of gerontology are:

• biology of aging - studies the general processes of aging of living organisms at different levels of their organization: subcellular, cellular, tissue, organ and organismal.
• Social gerontology is a field of gerontology that studies the influence of social and socio-cultural conditions on the aging process, as well as the social consequences of aging.
• geriatrics - the study of diseases of elderly and old people: the characteristics of their clinical course, treatment and prevention. Geriatrics also includes issues of organizing medical and social care,

Aging is a biological, destructive process that occurs as a result of the increasing damaging effects of exogenous and endogenous factors with age, leading to a decrease in the body's functions and its adaptability. Aging is universal for all living organisms and continues from inception to the end of existence.

This statement is also valid for humans. The process of fading is genetically programmed, i.e. it cannot be avoided, but it can be slowed down or accelerated.

Old age is a natural and inevitable final period of human development. According to the division of human life periods adopted by WHO, the age of 45-59 years is called middle, 60-74 years - elderly, 75-89 years - old, and people over 90 years old are considered long-livers.

Vitauct is a process that stabilizes the body's vital functions, increasing its reliability (counteracts aging).

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Age-related changes and their patterns

Heterochrony is the difference in the time of occurrence of destructive processes in tissues, organs and organ systems of one organism. For example: external signs of skin aging begin to appear from the age of 20, and age-related changes in the organs of vision are often recorded after 40 years.

Heterotropy - different expression for different organs and different tissues of the same organ in the body. For example: the same person may have pronounced age-related changes in the stomach, accompanied by atrophic processes and, at the same time, the structure and functional indicators of the respiratory organs may be quite intact.

Heterokineticity is the different rate of development of destructive processes in individual organs and systems. Thus, the skin ages over 40-50 years, and age-related changes in the central nervous system can progress over 10-15 years.

Heterocatephtism is the multidirectionality of processes associated with the suppression of the functional activity of some cells and the stimulation of other structural elements. For example: the glandular cells of the gonads produce less male or female sex hormones (respectively) with age, and the level of "tropic" hormones produced by the anterior pituitary gland increases.

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General mechanisms of aging

General mechanisms of aging are influenced by two mutually opposite, but dialectically united, processes: aging and vitauct. Aging leads to a decline in the intensity of metabolism, a decrease in functional capabilities and at the same time activates adaptive reactions - the vitauct process. This position underlies the adaptive-regulatory theory of aging (V.V. Frolkis). And life expectancy depends on the relationship between the processes of stabilization and destruction.

Tissue aging is characterized by such processes as atrophy, an increase in the amount of connective tissue or intercellular substance, the deposition of metabolic products (pigments, calcium, etc.), and the appearance of fatty degeneration. Primarily aging cells include nerve and connective tissue cells; muscle and glandular cells age as a result of increasing, over time, damaging effects and age-related changes in regulatory influences; aging of the epidermis and epithelium is caused by the entire complex of intraorgan influences (impaired blood circulation, nervous and humoral regulation, etc.).

Age-related changes in the adaptive and regulatory mechanisms of the body occur in three stages:

1. maximum voltage to maintain the range of adaptive capabilities;
2. decreased reliability: the body's adaptive capabilities are reduced while maintaining the level of basal metabolism and functions;
3. a decrease in the basal metabolic rate and body functions and a sharp limitation of the range of adaptability.

The concept of age in gerontology

Each person can be divided into the following types of age.

• Biological - reflects the functional state of organs and systems, determines the long-term ability to adapt and the reliability of the organism (a measure of the future ability to live).
• Calendar - the number of years a person has lived since birth.
• Psychological - a person's sense of belonging to a particular group, reflects the individual's ability to objectively assess the functional state of his body.

Age-related changes in each person are genetically programmed (determined by the species lifespan, hereditary information, possible mutations, etc.), but are not inevitably predetermined, since both the individual and the environment determine the acceleration or deceleration of aging processes. Age-related changes can be natural (biological age corresponds to calendar age), slow (leading to longevity) and accelerated (the severity of structural and functional processes in the body is ahead of calendar age). Age-related changes in various organs and systems are significantly expressed in old age.

A comprehensive assessment of the functional state of people of the “third” age includes determining the state of the following groups of parameters.

• Daily activities:
  • mobility;
  • useful daily activities, i.e. the ability to be an active member of society, coping with household chores;
  • daily physical activity, i.e. performing basic self-care activities.
• Mental activity, including:
  • cognitive activity;
  • severity of intellectual disabilities.
• Psychosocial functioning, i.e. emotional well-being in a social and cultural context.
• Physical health, including:
  • health status according to one's own assessment;
  • physical symptoms and diagnosed conditions;
  • frequency of use of health services;
  • activity level and assessment of self-care inadequacy.
• Social resources:
  • the presence of family, friends, and a familiar environment;
  • availability of these resources when needed.
• Economic resources that are typically measured by comparing income with an external measure such as the poverty rate.
• Environmental resources including:
  • adequacy and accessibility of housing;
  • the distance of the home from certain types of transport, shops and public services.

In geriatrics, to assess the effectiveness of treatment and preventive measures and actively monitor the health of patients, it is necessary to determine the biological age (BA) as a measure of the body's viability and compare it with the proper biological age (PBA - population standard of the aging rate according to V.P. Voitenko and A.V. Tokar). The development of accessible, informative, safe methods for determining PBA and PBA is an urgent task of gerontology.

Age-related changes in organs and systems

Changes in the respiratory system

In the respiratory tract:

• atrophy of the mucous membrane of the upper respiratory tract;
• slowing down of the movement of epithelial villi;
• reduction of glandular secretion, increase in its viscosity;
• the appearance of areas where the multi-row ciliated epithelium is replaced by stratified squamous epithelium;
• increasing the cough reflex threshold,
• decreased self-cleaning of the respiratory tract (slowing of mucociliary clearance and decreased effectiveness of immune responses);
• expansion of the lumen of the larynx, reduction of tension of the vocal cords (the voice deepens and becomes raspy);
• displacement of the larynx downwards (on average by one vertebra).

In the respiratory sections:

• the interalveolar septa are destroyed, the alveolar ducts expand - senile emphysema (increased airiness of the lung tissue) develops;
• connective tissue grows in the interalveolar septa, and pneumosclerosis develops;
• the blood vessels in the lungs change, their blood supply decreases;
• the volume of dead space and residual volume increases;
• the vital capacity of the lungs decreases;
• gas exchange disorders lead to a decrease in the oxygen content in arterial blood (hypoxemia);
• breathing increases to 22-24 per minute in old age.

Age-related changes in the musculoskeletal system of the chest:

• the mobility of the costovertebral joints decreases;
• calcium salts are deposited in the hyaline cartilage of the ribs;
• muscles weaken (due to degenerative changes);
• thoracic kyphosis increases;
• the chest loses elasticity, its anteroposterior diameter becomes equal to the transverse one (the shape of the chest approaches cylindrical).

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Age-related changes in the cardiovascular system

Age-related changes in the heart muscle:

• the contractility of the myocardium decreases; the cavities of the heart and the openings between them expand, the final systolic and diastolic volumes increase;
• heterotropic hypertrophy of cells develops, their contractile ability decreases, the isometric phase of contraction lengthens, and the relaxation index decreases;
• the systolic and minute volume of blood decreases (even under normal conditions the heart works with considerable stress); the connective tissue stroma increases (cardiosclerosis develops), the myocardial extensibility decreases:
• weakness of the sinus node (the first-order pacemaker) develops, the conduction of excitation through the myocardium slows down - the duration of systole increases, the number of muscle contractions becomes less frequent;
• the intensity of tissue respiration decreases, anaerobic breakdown of glycogen is activated, which leads to a decrease in the energy reserve of the heart muscle;
• In old age, muscle fibers atrophy and substitution obesity may develop.

Age-related changes in the vascular bed:

• the elasticity of the arteries decreases due to the thickening of their walls by overgrown connective tissue - vascular resistance and diastolic pressure increase;
• nutrition deteriorates, energy metabolism in the vascular wall decreases, the sodium content in it increases, which leads to the activation of the atherosclerotic process, a tendency to vasoconstriction (narrowing of the vascular lumen);
• the tone and elasticity of the venous wall decreases, the venous bed expands, the blood flow in it slows down (the return of blood to the heart is reduced, the risk of thrombosis is high);
• the number of functioning capillaries decreases - they become tortuous, arteriovenous shunting of blood increases (the transition of blood from the arterial bed directly to the veins through anastomoses, bypassing the capillaries), the basement membrane of the capillaries thickens, making it difficult to transport substances through it;
• lymphatic vessels become less elastic, and areas of expansion appear in them;
• cerebral and coronary circulation decreases to a lesser extent than hepatic and renal circulation;
• with aging, the sensitivity of vascular receptors to adrenaline increases, leading to the frequent development of spastic reactions and contributing to sharp changes in blood pressure;
• the total blood circulation time increases due to an increase in the capacity of the vascular bed and a decrease in cardiac output.

The adaptive function of the cardiovascular system is reduced, largely due to the inadequate functioning of the hemodynamic center (at the cortical, diencephalic and stem levels). Of course, reflex reactions of the cardiovascular system to various types of stimuli - muscle activity, stimulation of interoreceptors (change in body position, oculocardiac reflex), light, sound, pain irritation - in old people occur with a long latent period, are expressed much less, and are characterized by a wave-like and protracted course of the recovery period.

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Age-related changes in the digestive organs

Age-related changes in the oral cavity:

• gradual loss of teeth occurs, teeth acquire a yellowish tint and varying degrees of wear, the barrier properties of dental tissues are reduced;
• the alveolar processes of the jaws atrophy, the bite changes (becomes prognathic);
• the volume and secretion of the salivary glands decreases - this leads to a constant feeling of dry mouth, disruption of the formation of the food bolus, and a tendency to inflammation of the mucous membrane;
• the enzymatic saturation and protective properties of saliva decrease;
• chewing and digestion of food is impaired;
• The tongue becomes flat and smooth due to atrophy of the muscles and papillae; taste thresholds increase.

Gradually, the tonsils of the lymphoepithelial pharyngeal ring atrophy;

The esophagus lengthens and curves due to kyphosis of the spine, its muscular layer undergoes partial atrophy, which can lead to swallowing difficulties and a high risk of hernias (protrusions);

The stomach decreases in size, takes a position closer to horizontal. The number of secretory cells in the glands decreases (less hydrochloric acid, enzymes and gastric juice in general are produced). The blood supply to the stomach wall is disrupted, its motor function decreases.

In the small intestine, the relief of the mucous membrane is smoothed out due to a decrease in the height of the villi and their number per unit area (the surface of parietal digestion and absorption is reduced); due to a decrease in the secretion of digestive juices and their enzymatic saturation, the depth and completeness of food processing is disrupted.

In the large intestine, due to atrophy of muscle cells, there is a high risk of developing diverticula, a tendency to constipation develops; the intestinal microflora changes: the number of putrefactive bacteria increases, and lactic acid bacteria decreases, which contributes to the growth of endotoxin production and disruption of the synthesis of vitamins B and K.

Liver: with age, the mass decreases, the functional capabilities of hepatocytes decrease, which leads to disruption of protein, fat, carbohydrate and pigment metabolism, a decrease in the antitoxic (neutralizing) function of the liver. The amount of glycogen in the cells decreases, lipofuscin accumulates, Blood flow in the liver changes: some of the sinusoidal capillaries collapse, additional pathways from the interlobular veins to the central veins are formed.

The gallbladder increases in volume, muscle tone and motor activity of the bladder decrease - the timely flow of bile into the intestine is disrupted and the risk of stone formation increases due to bile stagnation.

The pancreas reduces its external and internal secretory function due to decreased blood supply and a decrease in the number of glandular cells and islet cells (older people have higher blood glucose levels).

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Age-related changes in the urinary system

Age-related changes in the kidneys:

• the number of functioning nephrons decreases (by 1/3-1/2 in old age), and age-related nephrosclerosis develops;
• the level of renal blood circulation and glomerular filtration decreases, excretory (nitrogen, water, electrolyte excretion) and concentration (due to a decrease in the tubular part of the nephron) functions of the kidneys decrease;
• the ligamentous apparatus of the kidneys weakens as a result of splanchnoptosis (prolapse of internal organs).

Age-related changes in the urinary tract:

• the renal calyces and pelvis lose elasticity, speed and strength of movement (due to atrophy of some muscle fibers);
• the ureters expand, lengthen, become more tortuous, their walls thicken, and the evacuation of urine from the upper urinary tract slows down;
• impaired motor function of the urinary tract and imperfection of the physiological sphincters cause frequent reflux (reverse (against the normal direction) flow of urine) in old age;
• the bladder wall thickens, its capacity decreases, the inhibitory effect of the cerebral cortex on the bladder receptors during night sleep weakens - this leads (along with an increase in nocturnal diuresis associated with processes in the cardiovascular system) to an increase in the frequency of urges to urinate at night. Various types of urinary incontinence often develop:
  • stress type - when coughing, laughing, exercises associated with increased intra-abdominal pressure;
  • motivating type - the inability to delay the contraction of the bladder (caused by a violation of the nervous regulation of its activity);
  • excessive type - caused by functional insufficiency of the internal and external sphincters of the urinary bladder;
  • functional type - in the absence of the usual conditions for urination or in the presence of physical or mental disorders in the patient.

A decrease in the contractile ability of the internal and external sphincters of the urinary bladder, the longitudinal muscles of the posterior urethra, and depletion of the vessels of the venous plexus of the bladder weaken the function of the occlusive apparatus of the urinary bladder, and changes in the vesicoureteral angle (due to disruption of the ligamentous apparatus of the urethra) facilitate the release of urine from the bladder and also contribute to the development of incontinence.

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Age-related changes in the endocrine system

With aging, hormone production, hormone binding to proteins, and reception by target cells change.

In the hypothalamus, lipofuscin accumulates in nuclear cells, the neurosecretory response to reflex (skin-pain) or nerve afferent stimuli weakens, and the response to humoral stimuli (e.g., adrenaline) increases. In the pituitary gland, the production of the "triple" hormones of the anterior lobe increases - thyroid-stimulating hormone (TSH), somatotropic hormone (STH), adrenocorticotropic hormone (ACTH), and others. In general, age-related changes in various parts of the hypothalamic-pituitary system are uneven.

The aging process in the thymus gland begins during puberty, and by old age its cortex almost completely disappears, which leads to a significant reduction in the capabilities of the immune system.

In the thyroid gland, the connective tissue stroma increases, the number of follicles and the fixation of iodine by the thyroid gland decreases, which leads to a decrease in the level of thyroxine and triiodothyronine in the blood (up to 25-40% after 60 years) - signs of hypothyroidism develop.

In the adrenal glands after 30 years, a structural reorganization of the cortex occurs, the fascicular (glucocorticoids) and reticular (produces sex hormones) zones increase, at 50-70 years the adrenal cortex is represented mainly by the fascicular zone, while the overall production of adrenal hormones and their adaptive reserves decrease.

The blood supply to the pancreas worsens, the number of cells in the islets of Langerhans and the biological activity of the insulin produced in them decrease. With aging, the blood sugar level increases.

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Age-related changes in the sex glands

From 18 to 80 years of age, spermatogenesis activity in the testes decreases; the testosterone content in the blood plasma gradually decreases and the level of testicular estrogens increases. The mass of the testicles decreases, but libido and sexual potency can be observed in men up to 80-90 years of age. In the prostate gland, connective tissue and muscle elements prevail over secretory ones, the mass and tendency to hypertrophy increase. In the ovaries, follicle atrophy occurs, they shrink, gradually turning into dense fibrous plates (starting from the age of 30, the secretion of estrogens decreases, and after 50 years, the secretion of gonadotropins increases).

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Age-related skin changes

Age-related changes in the skin begin after 20 years, increase after 40 years, become pronounced by 60-75 years and are especially evident at 75-80 years:

• the formation of wrinkles, furrows, folds is characteristic (starting with open parts of the body - face, neck, hands);
• graying of hair, baldness, increased hair growth in the eyebrow area, external auditory canal;
• in the epidermis the germ layer decreases and the stratum corneum increases;
• collagen fibers become coarser and homogenized in places;
• elastic fibrils thicken, shorten, and their lysis increases;
• connective tissue papillae are smoothed out, the subcutaneous fat layer is reduced, and pigment spots appear;
• blood vessels are visible through the generally thinned skin;
• the number of sebaceous and sweat glands decreases,
• the skin becomes dry;
• the lumen of the vessels of the dermis narrows significantly, their walls become sclerotic;
• in general, the skin becomes thinner and its protective properties are significantly impaired;
• the threshold of tactile sensitivity increases.

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Age-related changes in the hematopoietic system

Age-related changes in red bone marrow:

• the bone marrow space is gradually filled with fatty tissue;
• the activity of erythropoietic (hematopoietic) tissue decreases, but the maturation of red blood cells is maintained;
• granulocyte maturation does not change significantly (neutrophil cytopoiesis is slightly reduced);
• lymphoid hyperplasia occurs;
• the number of megakaryocytes decreases, but they function longer and more economically.

Age-related changes in the thymus gland:

• starting from the age of 16-20, the thymus undergoes reverse development, which is accompanied by a decrease in the number of lymphocytes, especially in the cortex of the lobules, the appearance of lipid inclusions in connective tissue cells and the proliferation of adipose tissue;
• the cortex atrophies significantly;
• the hematothymic barrier is often disrupted.

Age-related changes in the spleen:

• reticular fibers thicken, collagen fibers are formed;
• the red and white pulp gradually atrophies, the proliferation of T-lymphocytes weakens;
• the number of lymphoid nodules and the size of their germinal centers decrease;
• more iron-containing enzyme accumulates, reflecting the death of red blood cells.

Age-related changes in lymph nodes:

• thickening of the connective tissue capsule and trabeculae, myocyte atrophy and decreased motor function of the lymph node;
• signs of fatty degeneration of the superficial lymph nodes, leading to difficulty in lymph flow;
• in the cortex the number of lymphoblasts decreases, the number of macrophages, mast cells and eosinophils increases;
• Stabilization of aging processes in the lymph nodes occurs at the age of 60-75 years.

Age-related changes in blood:

• the lifespan of red blood cells increases to 154 days;
• the number of red blood cells in long-livers decreases slightly;
• the area of erythrocytes gradually decreases and the level of enzymes and hemoglobin in the cytoplasm of these cells decreases;
• the number of leukocytes and their activity decreases;
• in people over 70 years of age, the number of platelets decreases and their involution accelerates;
• in blood plasma the content of fibrinogen and gamma globulin increases and the level of albumin decreases;
• the rheological properties of the blood change, ESR increases to 40 mm per hour.

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Age-related changes in the musculoskeletal system

Age-related muscle changes:

• reduction in the number of muscle fibers and their diameter;
• increase in fatty inclusions and lipofuscin in muscle cells;
• a decrease in the number of functioning capillaries and neurons per muscle unit;
• ATPase activity of muscles decreases.

Age-related changes in bones:

• osteoporosis as a result of protein deficiency and a decrease in the content of minerals in tissues;
• enlargement of the epiphyses of tubular bones, formation of bone growths (hyperostoses and exostoses), thickening of the remaining bone beams;
• thoracic kyphosis and lumbar lordosis increase;
• the arch of the foot flattens, height decreases;

Age-related changes in joints:

• calcification of tendons and joint capsules;
• progressive degeneration of articular cartilage, narrowing of the joint space, decrease in intra-articular fluid;
• destructive age-related changes in the intervertebral discs and adjacent tissues (osteochondrosis develops).

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Age-related changes in the organ of vision

• Decreased elasticity of the lens and zonule, weakening of the ciliary muscle, leading to accommodation disorder; increase in the size of the lens and changes in its shape;
• presbyopia (on average 1 D every decade, starting from age 40); difficulty in the circulation of intraocular fluid, high risk of glaucoma (increased intraocular pressure); limitation of visual fields, decreased adaptation to darkness;
• weakening of the tone of the orbicularis oculi muscle, pumping function of the lacrimal canals - disruption of the timeliness of tear outflow.

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Age-related changes in the organ of hearing

• Hyperostosis and narrowing of the internal auditory canal;
• calcification of the articulations of the auditory ossicles and fibers of the basal membrane of the cochlea;
• decreased amplitude of movement of the eardrum;
• obstruction of the auditory tube; increased threshold of sound perception, especially high frequencies - development of presbycusis;
• weakening of the vestibular system, decreased sense of balance - dizziness, falls.

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Age-related changes in the nervous system

• The number of nerve cells gradually decreases: from 10-20% in 60-year-olds, to 50% in the elderly;
• dystrophic age-related changes in the cells of the nervous tissue increase: lipofuscin (a product of the oxidation of unsaturated fatty acids) accumulates in neurons, and senile amyloidosis of the brain develops (the appearance of a special protein in the cells - amyloid);
• focal demyelination of nerve fibers develops, which leads to a slowdown in the conduction of excitation along the nerve fiber and an increase in the reflex time;
• in various parts of the nervous system, the exchange of neurotransmitters (dopamine, serotonin and norepinephrine) is disrupted - this increases the risk of developing depression and Parkinson's disease;
• In the endbrain, atrophic age-related changes in the convolutions are observed, the sulci widen (this is most pronounced in the frontal and temporal lobes);
• The inhibitory influence of the cerebral cortex on the activity of subcortical formations is weakened;
• Old conditioned reflexes fade slowly and new ones are difficult to develop;

Memory, especially short-term memory, is reduced, which, along with other processes in organs and systems, reduces the ability to learn.

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