1, changes in the cardiovascular system As age increases, significant changes occur in the elastic arteries, especially the aorta, mainly including lipid deposits and fibrous tissue plaque formation in the arterial wall, thickening of the vessel wall, narrowing of the vessel; increased collagen in the middle layer of the vessel, reduced elastic fibers, reduced elasticity of the vessel wall, central arteriosclerosis leading to increased systolic and diastolic pressure, the vascular system can not buffer the heart beat and lead to ventricular afterload Increased ventricular afterload due to the inability of the pulsatile system to buffer the heart beat, eventually leading to left ventricular hypertrophy. At the same time, cardiac myocytes become hypertrophied and their number decreases due to increased vascular load. Diastolic filling pattern changes, the early diastolic filling rate of the left ventricle decreases with age, and the left ventricular ejection fraction decreases, which is a risk factor for heart failure, leading to left ventricular hypertrophy, atrial fibrillation and congestive heart failure occurring more easily in the elderly population, and the heart rhythm also changes due to autonomic regulation disorders in the elderly. 2, changes in the respiratory system The lung structure aging due to simple age increase: lung atrophy, alveolar cavity enlargement, alveolar wall thinning, capillary bed loss, alveolar wall elastic fiber reduction, collagen increase resulting in reduced lung tissue elasticity and reduced lung capacity. The combination of weakened alveolar and airway elastic retraction capacity and reduced respiratory muscle strength leads to increased residual air volume. Narrowing of the airways in the elderly, especially the lumen of the small airways, leads to increased airflow resistance. Mucous membrane and cilia shedding are reduced, bronchial secretions are not easily discharged, sputum is stored, and repeated infections form chronic bronchitis in the elderly, or secondary emphysema or pulmonary heart disease. At the same time, in the aging process, lung function also decreases with the aging changes of the respiratory system structure. 3. Changes in the digestive system Atrophy of the smooth muscle of the esophagus and weakened propulsive contraction lead to a weakened ability to push food. In the elderly, the lower esophageal sphincter is significantly weakened and leads to reflux of gastroduodenal contents. Atrophy of the gastric and small intestinal glands and reduced secretion of digestive juices lead to reduced digestive function. Gastrointestinal tract muscle atrophy, affecting food pushing and leading to constipation, poor nutrition, etc. 4, changes in the motor system Human bone mass changes with age from birth, generally from birth to 20 years old before, bone mass increases with age, bone density also increases significantly, and the rate of increase is greater in men than in women. For a period of time, bone density reaches peak equilibrium, i.e., the rate of bone formation and bone resorption is approximately the same, and then bone resorption is greater than bone formation, bone volume begins to decrease, and X-rays show obvious osteoporotic changes in bone mass in the elderly. Since estrogen is an important factor in stabilizing bone calcium, postmenopausal women have significantly lower bone mass than men. The bone salt component increases, the brittleness of bones increases, and fractures are likely to occur. At the same time, there can be osteophytes in the joints of the neck and lumbar spine, which compress the nerve roots and cause pain and unfavorable joint movement. Skeletal muscles may gradually atrophy and decrease in elasticity due to reduced activity, thus limiting the activities of the elderly. It has been found that the decrease in skeletal muscle may be related to the loss of mitochondria, and that articular cartilage gradually loses elasticity and flexibility as we age. Bone marrow adipose tissue also increases with age. 5. Changes in the endocrine system As age increases, endocrine glands atrophy and secretion function diminishes in old age, with gonadal changes being the most obvious. The production and degradation of hormones and the sensitivity of target organs to hormones all change differently, resulting in the disruption of the original balance in the body. Among them, due to the decrease in the number of beta cells, the sensitivity of pancreatic islets to glucose stimulation is reduced, therefore, the glucose tolerance of the elderly is reduced and the prevalence of diabetes increases with age. 6. Changes in the nervous system Nerve cells are not renewable and are filled by glial cells once they die. The death of a large number of nerve cells in the elderly leads to weight loss of the brain, widening of the brain sulcus, narrowing of the brain gyrus, degenerative changes in nerve fibers, shortening of synapses, slowing of nerve conduction speed and loss of sensation, and the formation of age spots due to pigmentation. In addition, the blood vessels in the brain become sclerotic, the walls of the blood vessels shrink, and the cerebral blood flow decreases, resulting in insufficient blood supply to the brain. As a result, the elderly often show disinterest in surrounding things, indifferent expressions, reduced memory, analysis and synthesis ability, inattention, shortened physiological sleep time, neurasthenia, menopausal syndrome and Alzheimer’s disease, etc. 7, changes in the immune system With age, the body’s immune system will degenerate, which can be manifested as a decrease in resistance to pathogenic microorganisms. The thymus gland begins to degenerate after sexual maturity, gradually fibrosis, weight loss, and eventually almost completely degenerated by the replacement of adipose tissue. The thymus is the organ where T-lymphocytes develop and mature, so its degeneration is the main reason for the decrease of T-lymphocytes, which leads to the decrease of the body’s immune function. Although the number of natural killer cells is not reduced, their ability to kill and secrete cytokines is significantly reduced, so the ability to resist infection and immune surveillance decreases in the elderly. In addition, humoral immunity gradually declines in aging. Although the number of B lymphocytes does not decrease significantly, the antibodies produced change from IgG to IgM, and the antibody affinity decreases.