1. Cellular Aging: Aging involves a gradual decline in the function and efficiency of cells throughout the body. This cellular aging affects various tissues and organs, not just the skin. Cells accumulate damage over time, which can lead to a wide range of age-related health issues.
2. Organ Decline: Aging impacts the functionality of vital organs such as the heart, lungs, kidneys, and liver. These organs play essential roles in maintaining overall health and can be affected by age-related conditions like cardiovascular disease, respiratory problems, and kidney disease.
3. Muscle and Bone Health: Muscles and bones also change with age. Muscle mass decreases, leading to muscle weakness and a decline in physical strength. Bone density may decrease, increasing the risk of fractures and osteoporosis.
4. Cognitive Decline: Aging is associated with cognitive changes, including a decline in memory, attention, and problem-solving abilities. Neurodegenerative conditions like Alzheimer's disease become more common with age.
5. Metabolic Changes: Metabolism tends to slow down with age, which can contribute to weight gain and an increased risk of conditions like type 2 diabetes.
6. Hormonal Changes: Hormonal fluctuations are a part of the aging process. Changes in hormone levels can affect various bodily functions, from reproductive health to mood regulation.
7. Immune System Weakening: The immune system becomes less efficient with age, making older individuals more susceptible to infections and less capable of fighting off illnesses.
8. Cardiovascular Health: Aging can lead to the development of cardiovascular diseases such as hypertension, atherosclerosis, and heart disease.
9. Vision and Hearing: Vision and hearing decline with age due to changes in the eyes and ears, leading to conditions like cataracts, presbyopia, and hearing loss.
10. Emotional and Psychological Changes: Aging can bring about emotional and psychological changes, including shifts in priorities, perspectives, and coping mechanisms. Mental health can also be affected. 
11. Genetics and Environmental Factors: Genetic predisposition and environmental factors, such as diet, exercise, and exposure to toxins, play significant roles in how an individual ages and the extent to which age-related changes occur.

In summary, aging is a multifaceted process that affects nearly every aspect of the human body, not just the skin. It involves a combination of genetic, cellular, physiological, and environmental factors that collectively contribute to the various physical and functional changes associated with getting older. Skin changes are just one visible aspect of this complex and natural progression of life.