Aging is a complex process that affects every part of our body, from the surface of our skin to the intricate systems working underneath. In Part One of this series, we discussed the external and internal changes related to the musculoskeletal, cardiovascular and respiratory systems. However, many significant changes also occur within our immune, nervous and digestive systems: ones that can profoundly affect our quality of life as we grow older. In Part Two of the series, we’ll explore what these systems do, the changes that occur with age and how they can influence your health. 

Immune System 

When your partner or little one comes home with a sudden fever and sore throat that turns into the flu, you can thank your immune system if you manage to stay flu-free. (Of course, you may also end up cursing that same system if you catch the illness yourself.) 

The immune system plays a critical role in defending your body against pathogens like the cold and flu and helps you recover faster if you do get sick. It consists of several crucial parts, including: 

• White blood cells 
• Antibodies 
• Lymph nodes 
• Spleen 
• Tonsils and adenoids 
• Bone marrow 
• Skin 

Some components, such as the skin, tonsils and adenoids, serve as the first line of defense against germs, acting as protective barriers. However, if pathogens manage to get past these barriers, other parts of the immune system, like white blood cells and lymph nodes, spring into action, attacking harmful germs to eliminate the infection. 

As you age, your immune system’s response begins to slow. Your body produces fewer white blood cells and other cells that fight viruses and bacteria, making you more vulnerable to illnesses. Additionally, when you do get sick, recovery often takes longer due to the slower immune response.  

Nervous System 

The nervous system is the body’s communication hub. It transmits signals between the brain and the rest of the body and is responsible for voluntary actions, like talking or walking, and involuntary actions, like digestion. It also controls your thoughts and memories. 

The two main parts of the nervous system include: 

• Central Nervous System (CNS) 
  Made up of the brain and spinal cord, the CNS processes and interprets information and sends out instructions to the rest of the body. 

• Peripheral Nervous System (PNS) 
  Consisting of nerves that travel through the head, neck and body, the PNS works like a communication highway, carrying information to and from the CNS. 

As you age, your brain’s overall function begins to slow, making it more challenging to process new information or transition between tasks. Some older adults also experience memory decline, sometimes leading to cognitive disorders like dementia, with Alzheimer’s being the most common form. 

Furthermore, reflexes and response times may also slow due to less efficient neural communication. When signal transmission between the PNS and CNS becomes sluggish, it can lead to decreased coordination and difficulty with balance.  

Digestive System and Metabolic Changes 

The digestive system plays a crucial role in absorbing the nutrients from the food you eat, breaking it down and converting it into waste (a.k.a. feces) to be eliminated from the body during bowel movements. 

But how does the digestive system work? Here’s a breakdown: 

1. Food passes through your mouth and esophagus into the stomach, where it’s broken down into a more digestible form.  
2. It moves into the small intestine, a 22-foot-long tube that further processes the food, transforming it from a semi-solid state to a liquid form.  
3. The body absorbs essential nutrients like carbohydrates, proteins, fats and vitamins. 
4. Nutrients are sent to the liver, which processes them and produces the chemicals your body needs to function.  
5. The remaining waste continues to the large intestine (colon), where it is broken down further and eventually becomes stool.  
6. The feces are stored in the rectum until they’re expelled through the anus. 

Though this system functions efficiently, aging causes the digestive system to decline in several ways: 

• Your metabolism slows down, which can result in weight gain and constipation. 
• The production of digestive enzymes also slows down, making it more challenging to digest food. This can lead to more frequent bloating and indigestion. 
• Your body’s ability to digest nutrients also decreases, which may lead to vitamin deficiencies and an increased risk of conditions like osteoporosis and anemia. 

Take a Deep Dive Into the Functions of the Human Body at UF 

If you’re fascinated by the physiological effects of aging, considered a career in the medical sciences. From becoming a physician assistant to working in the biomedical devices industry, numerous career paths are available to those with a background in anatomy and physiology. 

The University of Florida proudly offers seven online graduate programs in the medical sciences. Many of them can be completed in as little as one year, and all allow you to study on your timeline. With year-round start dates, affordable tuition options and an education from Forbes’ No. 4 university in the nation, what’s stopping you from pursuing a career you’re passionate about?  

Explore our program offerings and choose the program that aligns with your goals. 

Sources:
https://medlineplus.gov/ency/article/004008.htm
https://www.lung.org/lung-health-diseases/how-lungs-work/lung-capacity-and-aging
https://www.health.harvard.edu/blog/surprising-findings-about-metabolism-and-age-202110082613
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2267679/ 

If you finally get around to sorting through those old boxes in your garage, you might stumble upon photos of you and your loved ones over the years. As you sift through them, you’ll likely notice physical changes: graying hair, fine lines, and maybe even a few extra pounds. 

But what about the changes no photo can capture? While a picture might be worth a thousand words, it can’t tell the full story of how time affects the body on a deeper, physiological level. Let’s take a closer look at some of the body’s systems and the physiological effects of aging to better understand the full impact of getting older.  

Exterior Changes 

As we age, changes to our outer appearance are often the most noticeable: 

• Skin 
  At 30, you could probably bump your arm on the sharp edge of the countertop and walk away unscathed. Two decades later, the same accident might result in an unwanted scratch or bruise. This is due to a reduction in collagen production, which makes the skin less elastic and more prone to scrapes and bruises. Additionally, thinning skin heals more slowly as we age. 

• Hair 
  After 35, you’re likely to notice more gray hairs. While some of us find them well before 35—or if we’re lucky, after—it’s not due to stress. Rather, our hair follicles produce less color as we age. So, if your hair was once a rich brown, you may see more strands turning gray with each new growth cycle. 

Musculoskeletal System 

The musculoskeletal system is made up of the body’s bones, muscles, tendons, cartilage, joints and other connective tissues. It plays a vital role in several functions essential for survival and quality of life: 

• Maintaining our posture 
  Muscles support the spine, helping to keep the body upright and stable. 

• Circulating our blood  While the circulatory system transports blood, the cardiac muscle — a part of the musculoskeletal system — pumps it throughout the body. 

• Being mobile 
  You can thank your bones, muscles and other parts of the musculoskeletal system for your ability to walk and run. 

• Breathing 
  The diaphragm, a key muscle in the system, contracts and relaxes to help the lungs fill with air for respiration. 

Unlike exterior body parts, like our skin and hair, the musculoskeletal system shows signs of internal aging in the following ways: 

• Muscle mass 
  Even with decades of consistent exercise, you might notice a loss of muscle mass or ‘tone’ over time. This is due to changes in muscle tissue, which becomes harder to contract efficiently as you age, leading to decreased strength and stamina. 

• Bone density 
  Bone mass naturally declines with age, particularly in women after menopause. The decrease in estrogen levels can lead to a rapid reduction in bone density — up to 10% in the first five years post-menopause — making bones more fragile and increasing the risk of fractures. 

• Joint health 
  Once enjoyable activities, like taking an afternoon nap, can quickly become less appealing — especially when your joints become painful and stiff afterward. In your youth, joints are well-lubricated by synovial fluid. As you age, this fluid decreases in quantity and quality, which can lead to stiffness and reduced mobility in the joints. 

Cardiovascular System 

The cardiovascular system is a complex network comprising the heart, arteries, veins and capillaries. Each component plays a vital role in circulating blood throughout the body, ensuring that oxygen and nutrients are delivered to cells while also removing waste. 

Our cardiovascular system works tirelessly from before birth. With the average heart beating 100,000 times a day, it’s no surprise that this hardworking system eventually shows signs of aging. Key changes include: 

• Declining heart health 
  One major age-related change is the thickening of heart walls, which makes it harder for the heart to pump blood efficiently. Additionally, the arteries that carry oxygen-rich blood tend to stiffen and lose elasticity over time, reducing the cardiovascular system’s ability to regulate blood pressure effectively. 

• Higher blood pressure 
  Over time, you may notice a gradual rise in blood pressure during routine checkups. While this increase is a natural part of aging — often influenced by hardening arteries, genetics and lifestyle factors — it can become problematic if it reaches hypertension levels. At that point, it becomes a significant risk factor for cardiovascular diseases. 

Respiratory System 

Your ability to breathe is made possible by your respiratory system, which includes the lungs, airways, diaphragm, larynx, throat, nose and mouth. While its main function is to exchange oxygen for carbon dioxide, the respiratory system also plays a role in: 

• Protecting you from germs and tiny allergens such as dirt and pollen. 
• Helping you speak. 
• Using your sense of smell. 

With time, many of the normal functions of the respiratory system begin to decline. You may notice minor changes, such as a decrease in your ability to smell some of your favorite (and not-so-preferred) scents, especially after age 70. 

However, more serious declines may occur in the lungs. They mature around age 25 and begin to decline gradually around age 35, often due to the following changes: 

• A weakening diaphragm, the muscle responsible for breathing. 
• Lung tissue losing elasticity, making airways narrower and air passage slightly more difficult. 
• Shrinking rib bones, which provide less room for lung expansion. 

Advance Your Understanding of Medical Sciences at the University of Florida 

The body systems discussed here are just a glimpse of the intricate mechanisms that keep us functioning. Several other integral systems also experience changes as we age, impacting our overall health and well-being. Join us for part two of our series, where we’ll explore even more inevitable physiological changes and what they mean for our aging bodies. 

If you’re passionate about understanding the complexities of the human body and want to apply this knowledge in fields such as medicine, education, public health or biomedical research, the University of Florida offers seven online graduate programs that provide the perfect opportunity to advance your expertise. Whether you’re drawn to our master’s degree in medical physiology and aging or our Graduate Certificate in Medical Human Anatomy, our programs are designed to fit your interests and prepare you for success in your chosen career path. 

Ready to take the next step in your journey? Apply today and unlock your potential in the field of medical sciences. 

Sources:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1606623/
https://www.health.harvard.edu/blog/hair-turn-gray-2017091812226
https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/menopause-and-osteoporosis
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2579627/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3593048/ 
https://www.lung.org/lung-health-diseases/how-lungs-work/lung-capacity-and-aging
https://www.bhf.org.uk/informationsupport/how-a-healthy-heart-works 

One moment, you’re scouring your phone’s camera roll for the infamous cake-in-the-hair photo of your kiddo on their first birthday. The next thing you know, you’ve spent an hour absorbed in eight years’ worth of photos, and you’re left wondering where those eight years went. 

As you watch time fly via photo slideshow, you may also notice a few extra fine lines or gray hairs where there were none a few years ago, which begs the question: Why do we age? 

Today, we’re exploring five factors that contribute to the aging process. 

#1 Genetics 

Our genes are one of the main components that impact how and why we age, with each individual’s unique genetic combinations playing a role in determining our overall lifespan. For example, some individuals are born with robust cellular repair mechanisms. This allows them to physically age at a slower rate than those that have less efficient DNA repair mechanisms. 

#2 Hormonal Changes 

Our bodies use hormones to help us complete a myriad of functions, from regulating our metabolism and reproduction to influencing our mood and sleep patterns. Over the years, our hormone production begins to decline.  

Below, we discuss how lower numbers of certain hormones can exacerbate aging. 

Estrogen and Testosterone 

These well-known sex hormones are responsible for more than their fundamental role in helping us reproduce. They also play a part in regulating our bone health and cognitive function. As women age, their estrogen levels lower. This makes them more likely to experience signs of aging in the form of bone loss. For aging men, however, the loss of testosterone can decrease muscle mass and libido, contributing to declines in overall physical function. 

Growth Hormone (GH) 

As you might expect, GH is crucial during our formative years, as it regulates our metabolism and body composition as we grow into our adult bodies. But like with most internal processes, GH declines with age. 

In turn, our metabolic rate may decrease, leading to an accumulation of fat. Depleted GH production can also impair our bodies’ ability to repair tissue, which can contribute to age-related declines in muscle mass, skin elasticity and bone density. 

#3 Chronic Inflammation and Aging

When we get sick or scrape our knees, our bodies get straight to work to repair the damage by initiating an inflammation response. That’s because, as children, our cellular repair capabilities are in their prime. 

As adults, however, our bodies sometimes initiate low-level inflammation even when there’s no infection to fight against. That inflammation can last for days, months or even years at a time. This continuous low-grade inflammation causes what’s known as inflammaging, which makes some individuals more prone to certain age-related diseases and accelerated aging. 

#4 Environmental Factors 

It’s hard to pass up some of life’s simple pleasures, like soaking in the warm rays of the summer sun or treating yourself to an extra glass of wine. However, some of those indulgences contribute to the aging process. 

For instance, the sun’s ultraviolet rays introduce unstable molecules, called free radicals, into our skin. Over time, free radicals have the potential to damage your DNA, which can cause premature aging, wrinkles and cancer. 

Other environmental factors that can cause signs of aging include air pollution and exposure to carcinogens, such as cigarette smoke. 

#5 Lifestyle Choices 

We can’t control how our genes impact the aging process, but we can control some of the lifestyle choices that affect how we age. Below, we explore how some of these can impact you negatively if neglected:  

• Diet 
  A diet that consists largely of processed foods, unhealthy fats and sugar can accelerate internal cellular damage. This increases the likelihood of developing diseases that speed the rate of aging, such as diabetes, obesity and cardiovascular disease. 

• Physical activity
  A sedentary lifestyle can prematurely contribute to muscle loss, decreased mobility and age-related diseases.  

• Sleep
  Your body needs ample sleep (at least seven hours) to function at maximum capacity. Getting less than that for an extended period can disrupt your body’s natural circadian rhythm, increasing the risk of accelerated brain aging, a condition that occurs when your brain ages faster than your chronological age. This can lead to cognitive decline and memory impairment. 

Fortunately, you can control the lifestyle aspect of aging. With an improved diet, regular exercise and adequate sleep each night, you’re doing your part to slow the inevitable process of aging. But if you want to dive deeper into other mysteries of the human body, why not turn your fascination into a career? 

Unravel the Body’s Many Medical Mysteries at the University of Florida 

UF’s College of Medicine is proud to offer several entirely online graduate programs that focus on medical physiology. Each program enables you to embrace your passion and gain the foundational knowledge and skills to begin a career in medicine, from becoming a physician to pursuing a role as a clinical scientist — and so much more. 

Below, you can browse our diverse range of online graduate degree and certificate programs: 

• Master’s Degree in Medical Physiology and Pharmacology 
• Master’s Degree in Medical Physiology and Aging 
• Graduate Certificate in Medical Physiology 
• Graduate Certificate in Medical Physiology with a specialization in Cardiovascular/Renal Physiology 

Our programs are asynchronous and affordable, and we offer year-round start dates. Choose the program that’s right for you, and apply today! 

Sources:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3295054/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5850851/
https://www.nature.com/articles/s41574-018-0059-4
https://pubmed.ncbi.nlm.nih.gov/8865143/
https://pubmed.ncbi.nlm.nih.gov/16670164/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6305861/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7698794/
https://www.sciencedirect.com/science/article/pii/S0197458022000264
https://www.mayoclinic.org/healthy-lifestyle/adult-health/expert-answers/how-many-hours-of-sleep-are-enough/faq-20057898